First: thank you for registering on the RASNZ web site. For RASNZ members this is the first step toward gaining access to the RASNZ Members only area of the site. The next step is that the site administrators will notice your registration and add you to the Members group - as a RASNZ member you don't need to do anything more. This will usually happen within a day, but may occasionally take longer if our membership officer is not available. If the process is taking too long and you are anxious to get access to Southern Stars please This email address is being protected from spambots. You need JavaScript enabled to view it. who will get it sorted for you pending confirmation by the membership officer.

If you aren't yet a member of RASNZ we don't yet offer much "extra" on the site, although we are thinking about what we can provide for you. If you have ideas about what you would like to see please This email address is being protected from spambots. You need JavaScript enabled to view it. and we'll see what we can do for you. Otherwise you might consider joining the society. See Glen Rowe's article outlining the benefits of membership.

Anyway, have a fun, inspiring and educational time visiting our site and please let us know what you like or would like to see improved.

Welcome to the Royal Astronomical Society of New Zealand website.

The RASNZ website provides astronomical information with a New Zealand and Southern Hemisphere focus for members of the RASNZ and for people interested in astronomy and astronomical events generally.

Registered RASNZ members have access to the online version of the Southern Stars (RASNZ journal) and other member specific information.

Hey! How did I get here?

Some of the pages from our old site (from before 2014) haven't made it across to this site. Please This email address is being protected from spambots. You need JavaScript enabled to view it. and let us know which page you were looking for so we can provide it for you.

Please Register

Please take the time to create an account, especially if you are a RASNZ member.  For RASNZ members this opens up a members only section of the website where you can download the latest Southern Stars journal. We also provide various RASNZ documents for member's use. If you think there is something missing that we should provide to members please This email address is being protected from spambots. You need JavaScript enabled to view it. and let us know!

If you are not a RASNZ member now would be a good time to sign up for membership. You can do this using the online membership application form found under the RASNZ heading.

If you belong to a society affiliated with RASNZ note it during registration and we will keep you informed of upcoming events by email as information comes to hand.

We are here to help

Please do tell us (by emailing the This email address is being protected from spambots. You need JavaScript enabled to view it.) about any issues or missing material you notice. We would also love to hear about ideas for content you may have.

Take some time to have a look around, and come back again soon as we develop and grow the site.

Clear Skies,
Peter J. & Simon L.

RASNZ Electronic Newsletter November 2017

The RASNZ Email newsletter is distributed by email on or near the 20th of each month. If you would like to be on the circulation list This email address is being protected from spambots. You need JavaScript enabled to view it. for a copy. The latest issue is below.

Email Newsletter Number 203

Affiliated Societies are welcome to reproduce any item in this email newsletter or on the RASNZ website http://www.rasnz.org.nz/ in their own newsletters provided an acknowledgement of the source is also included.

Contents

1. First Interstellar Asteroid
2. Upcoming Astronomy Camps, Star Parties
3. Treasurer Sought
4. RASNZ Administrative Deadlines
5. Back Issues of Southern Stars Wanted
6. BAA Membership Search
7. Impact of Blue Light LEDs
8. The Solar System in December
9. Variable Star News
10. Solar Storms and Auckland's Damaged Fuel Pipeline
11. NZ's Stargazing Places Reviewed
12. Surprising Science from Cassini's Grand Finale
13. How to Join the RASNZ
14. Email Address Changes, Please
15. Next Newsletter December 16
16. Quotes

1. First Interstellar Asteroid

The first asteroidal object from interstellar space has been discovered. Previously only some dust, recorded as micro-meteors, has been known to come from beyond the solar system.

On October 18 the Pan-STARRS 1 telescope on Haleakala, Hawaii, found an asteroidal object moving in a comet-like orbit. It was given the comet designation C/2017 U1. However its orbit was much too hyperbolic, the object was going much too fast, to be comet from the outer edge of the solar system. Also long exposure images taken with the Very Large Telescope in Chile showed that it wasn't a comet. No fuzziness could be seen, it looked totally asteroidal, so it was re-designated A/2017 U1.

The shape of an orbit is described by its eccentricity, 'e'. A circular orbit has an eccentricity of 0. The main planets have orbital eccentricities of less than 0.1 except for Mercury for which e = 0.21. With few exceptions comets have orbital eccentricities near 1. Long- period comets, those taking centuries to return, have orbits shaped like long thin cigars. Their orbital eccentricities are a fraction less than 1.

An eccentricity of 1 is a parabola, a cigar-shaped curve at the sun end but with the inward and outward tracks never closing together at great distances. Comets approaching the Sun from far away move in almost parabolic orbits. A small nudge by the gravity of a planet can easily speed up the comet slightly or slow it down. If it is speeded up then its orbit becomes hyperbolic: it has an eccentricity slightly bigger than 1 and enough speed to escape the Sun's gravity altogether.

Comets that have come from far way often appear to be in hyperbolic orbits when they are near the Sun. This is because, on their way in, they are being accelerated by the combined gravity the Sun and the planets. That makes the gravity pull 0.1% stronger than the Sun's gravity alone. So a comet's orbital eccentricity might be as great as 1.005 when near the Sun but reverts to less than 1, an elliptical orbit, as it moves away from the Solar System and has the combined gravity of the Sun and planets slowing it down.

The most extreme hyperbolic orbit previously observed was that of Comet Bowell (C/1980 E1) which had an eccentricity near 1.05. But that was due to it passing just 0.23 AU, 35 million km from Jupiter and picking up extra speed.

The orbit of A/2017 U1 has an eccentricity of 1.19. To have this orbit shape it must have already been travelling toward the Sun at 26 km/sec when it was first acted on by the Sun's gravity. Before discovery it had passed just 0.25 AU or 38 million km from the Sun on September 9. Given its small size, estimated from its brightness to be around 160 metres, it was lucky to survive the cooking.

Running the object's trajectory backwards in time finds that it entered the solar system from the direction of the constellation Lyra, within ½° of right ascension 18h 44m, declination +34°40'. That's 4½° from the present position of Vega.

More intriguing is the fact that A/2017 U1 is coming from a spot only 6° from the solar apex, the direction that our Sun is moving (at about 20 km/s) through its interstellar neighbourhood and thus, statistically, the most likely incoming direction for an interstellar visitor.

Interstellar asteroids are no real surprise. We know that stars like the Sun form proto-planetary disks during their formation. The stars are also relatively close together in their early stages so close encounters would be common. These would allow outer planets or planetesimals to be removed. The MOA microlensing survey at Mt John has found evidence of several Jupiter-sized planets in interstellar space. Because the space between the stars around us is so big the chance of any of interstellar object, even a small one, coming close enough to be seen is very low but, as A/2017 U1 has shown, not zero.

-- Some bits of the above cribbed from Kelly Beatty's article at http://www.skyandtelescope.com/astronomy-news/astronomers-spot-first-known-interstellar-comet/ The discovery announcement and first orbital elements are in Minor Planet Electronic Circular 2017-U181.

2. Upcoming Astronomy Camps, Star Parties

 

-- From 'Keeping in Touch' #23, 1 October 2017.

3. Treasurer Sought

Retiring RASNZ Treasurer Simon Lowther writes:

After eight years in the position I will be retiring as the society's treasurer. I am happy that I am leaving the post with the society in a healthy financial position and can see that a new burst of enthusiasm will continue the growth of the last few years.

Please consider giving something back to this society that gives to the NZ astronomical community by putting your name forward at the next conference.

4. RASNZ Administrative Deadlines

February 3 is the deadline for the following: RASNZ Fellow nominations - RASNZ Rule 19 RASNZ Honorary Members nominations - RASNZ Rule 11 RASNZ Murray Geddes Prize nominations - RASNZ By-Law G5 Nominations of RASNZ Officers for 2018-20 - RASNZ Rule 74 Earth & Sky Bright Star Award - RASNZ By-Laws K

Feb 15 RASNZ Section and Group reports due to the Secretary - RASNZ By-Law F14 Mar 15 SWAPA applications deadline (for high school students) - http://www.rasnz.org.nz

-- From Keeping in Touch #24, 18th November 2017

5. Back Issues of Southern Stars Wanted

Leonard Matula, a US collector of astronomical publications would appreciate the following editions to fill gaps in his collection. If anyone can help, please send them to Bob Evans (address below) and he will pass them on. Volume 51 (2012) numbers 1, 3 and 4 Volume 52 (2013) numbers 2, 3 and 4 Volume 53 (2014) numbers 1, 3 and 4 Volume 54 (2015) numbers 1 and 4 Volume 55 (2016) numbers 1, 2 and 3

In addition, if anyone can supply him with earlier editions of Southern Stars, that is Volumes 1 to 50, please contact Bob for Leonard's contact details and further information.

Bob's postal address: 15 Taiepa Road, Otatara, RD9, Invercargill 9879. Email This email address is being protected from spambots. You need JavaScript enabled to view it..

6. BAA Membership Search

Anthony Kinder writes: I am currently researching the membership of the British Astronomical Association (BAA) since it was founded in 1890. Included in this is any and all information I am able to obtain about the person concerned. There are a number of New Zealander's who were members (e.g. Leslie J. Comrie, John Grigg). I would be interested in hearing from any RASNZ member who is or was in the past (or even considering joining in the future) a member of the BAA.

Send replies to Anthony at This email address is being protected from spambots. You need JavaScript enabled to view it.

7. Impact of Blue Light LEDs

The Royal Society of New Zealand has started developing expert advice to summarise the latest evidence on the impact of blue light wavelengths from LEDs. This could cover issues such as the impacts of: - LED screens and lighting on sleep patterns - LED street lighting on the nocturnal environment - blue wavelength light pollution on New Zealand's astronomy. For further information contact Dr Marc Rands This email address is being protected from spambots. You need JavaScript enabled to view it.. https://royalsociety.org.nz/what-we-do/our-expert-advice/our-expert-advice-under-development/impacts-of-blue-light/

-- Forwarded by Steve Butler

8. The Solar System in December

Dates and times shown are NZDT (UT + 13 hours) unless otherwise stated. Times are for Wellington. They will vary by a few minutes elsewhere in NZ.

The southern summer solstice is on December 22 with the Sun appearing furthest south at 5.28 am, about 12 minutes before sunrise at Wellington.

             December  1  NZDT          December 31  NZDT
      SUN:  rise 5.40am, set 8.39pm    rise 5.47am, set 8.59pm

Twilights    morning     evening        morning     evening
Civil:    start 5.10am, end 9.10pm   start 5.17am, end 9.31pm
Nautical: start 4.28am, end 9.52pm   start 4.34am, end10.14pm
Astro:    start 3.40am, end10.41pm   start 3.42am, end11.05pm

December Phases of the Moon (times NZDT, as shown by GUIDE)

  Full moon:     December  4 at  4.47am (Dec  3, 15:47 UT)
  Last quarter   December 10 at  8.51pm (07:51 UT)
  New moon:      December 18 at  7.30pm (16:30 UT)
  First quarter: December 26 at 10.20pm (09:20 UT)

The Planets in December 2018

Of the five naked eye planets only Mars and Jupiter will be far enough from the Sun for viewing and they are in the morning sky. Mars will be the better placed, especially early in the month.

Mercury, Venus and Saturn are all close to the Sun and at best make difficult objects. Mercury and Saturn are in the early evening sky at the beginning of December but reach conjunction during the month.

MARS starts December in Virgo rising more than two hours before the Sun. On the 1st it will be 3° below Spica, the planet being the fainter object at magnitude 1.7 compared to Spica's 1.1. On the 21st Mars will cross into Libra. By the 31st it will rise 3 hours before the Sun

During December Mars will be catching up with Jupiter, they are 16° apart on the 1st but only 3° apart on the 31st.

JUPITER is in Libra all month. It rises just over 80 minutes before the Sun on the 1st. This is close to the start of nautical twilight so Jupiter will not be an easy object low in the twilit sky. By the end of December Jupiter rises more than 3 hours before the Sun, only 9 minutes after Mars. The two planets will be more than 20° up an hour before sunrise, Jupiter more than 3 magnitudes brighter than Mars.

The crescent moon will be some 5° below Mars on the morning of the 14th and a similar distance from Jupiter the following morning, also Vesta will be less than a degree to the right of the moon.

MERCURY starts the month as an evening object setting nearly 2 hours after the Sun. 45 minutes after sunset, Mercury at magnitude 0.0 will be 8° above the horizon towards the west-south-west. On the 3rd of December, the planet is stationary, after which it starts moving to the west towards the Sun which itself will be moving to the east. Their separation will decrease rapidly over the next few days until Mercury is at inferior conjunction with the Sun on the 13th. At conjunction Mercury will pass 1.5° north of the Sun.

After conjunction Mercury will be a morning object. By the end of the month it will rise 85 minutes before the Sun, so will be a very low object a little to the south of east as the sky brightens.

SATURN will also finally disappear from the evening sky during December. On the 1st it will be nearly 3° to the lower right of Mercury, making Saturn even more difficult to see. It is at conjunction with the Sun on the 22nd. After conjunction it too becomes a morning object but will be too low for easy observation rising only half an hour before the Sun on the 31st.

VENUS is close to the Sun all month. It rises 28 minutes before the Sun on the 1st. This reduces to only 11 minutes earlier on the 31st.

Outer Planets

URANUS is in Pisces during December. It is well placed in the evening sky once it is dark. It sets about 1.45 am at the end of December.

NEPTUNE is also an evening object setting about 100 minutes before Uranus. So at the end of December it sets just after midnight. The planet is an Aquarius at magnitude 7.9.

PLUTO, magnitude 14.5, remains in Sagittarius. By the end of December it sets only have an hour after the Sun.

Brightest Minor Planets

(1) CERES is a morning object in Leo, brightening from magnitude 8.1 to 7.5 during the month. (2) PALLAS is in Fornax during December. It dims a little from magnitude 8.4 to 8.7 during the month. (4) VESTA is in Libra during December quite close to Jupiter. At their closest on December 11, Vesta will be about 4° from the gas giant. Vesta at magnitude 8 will rise two and a half hours before the Sun on the 31st. (7) IRIS dims from magnitude 7.8 to 8.6 during December. The asteroid is an evening object in Aries. (8) FLORA is a morning object brightening from magnitude 9.1 to 8.3 during December. It is in Gemini two days short of opposition on the 31st. (20) MASSALIA starts December in Orion at magnitude 9.0. It crosses into Taurus on the 11th, reaches opposition on the 17th with a magnitude 8.4 and fades to 8.9 by the end of the month. It is in the sky most of the night.

-- Brian Loader

9. Variable Star News

The latest Variable Stars South (VSS) Newsletter, 2017 No 4, October is now available from the website - https://www.variablestarssouth.org/ All newsletters can be found under the Tab Community; heading Newsletters and click on the particular newsletter image to download. The current newsletter has articles on some interesting stars: - Discussion of QZ Car, a quadruple system originally discovered at Auckland Observatory in the late 1960s. The published paper is Walker et al (2017) MNRAS 470.20074 - Consideration by Carl Knight of early ejection sequences of classical novae (the rising arm) with particular reference to Nova V5589 Sgr. - There is an analysis of the effect on observations of the 'one-day? orbital period phenomenon with V803 Cen, a pair of helium white dwarf stars.

As well as articles on a few other variables there is Part 3 of Mark Blackford's series on construction of his roll-off roof observatory at Congarinni, NSW, and its equipment.

-- Alan Baldwin

10. Solar Storms and Auckland's Damaged Fuel Pipeline

Physicists at Victoria University of Wellington and the University of Otago suggest geomagnetic storms can cause corrosion in New Zealand's pipelines, and some areas, including Northland, are more vulnerable.

Victoria's Dr Malcolm Ingham and Otago's Professor Craig Rodger are mid-way through a Government-funded research project that focuses on reducing the damage to electrical networks from currents induced in the ground by large geomagnetic storms. "When a solar eruption from the sun, for example, hits the Earth's magnetic field, it can cause rapid changes in the Earth's magnetic field'a magnetic storm," says Professor Rodger. "We're really vulnerable to these as we've become more and more technologically dependent. It can affect not only our power network, but also things like satellite communications."

However, Dr Ingham points out that because of the process of electromagnetic induction, currents induced in the Earth can also impact pipelines. "If there's a break in the pipeline's cladding, currents that travel from the pipe to the ground can cause corrosion of the pipe. To stop that happening, pipelines have power sources along them to keep the voltage of the pipe negative relative to the voltage of the ground. "However, more than 20 years ago, we carried out research that showed that the currents induced by geomagnetic activity cause the voltage of the ground to vary such that at times the pipe voltage becomes positive relative to the ground. This means that if you've got a hole in a pipeline cladding, variations in the geomagnetic field will cause corrosion over time, leading to containment failure and leakage."

New Zealand's geography controls the location and size of electrical currents in the ground, he adds. "Induced currents are typically larger in directions perpendicular to the coastline. Auckland and Northland are therefore especially vulnerable to such variations, because of the narrow make-up of the land."

Dr Ingham says last month's damaged fuel pipeline in Northland is probably an example of how pipelines can be affected by geomagnetic storms if the pipe cladding is damaged. "If a digger has previously, even years ago, scraped the coating of that pipeline, each geomagnetic storm since could have caused a little bit more corrosion and eventually it would give. That event also happened a few days after there was a big geomagnetic storm. To me, the effects of geomagnetic storms is something that should be considered when investigating the cause of the incident." More research needs to be done into how to mitigate corrosion to pipelines due to changes in the geomagnetic field, the researchers say.

Professor Rodger leads the Otago Space Weather research group and the Government-funded joint project into the potential damaging effects of "solar tsunamis" on the nation's electrical network. He says that pipeline corrosion is indeed another infrastructure impact that deserves careful investigation.

"While solar disturbances May create auroras beautiful to behold, the flip-side is that such awesome spectacles involve mind-numbingly amounts of energy suddenly flooding our geomagnetic field. Those changes could potentially play havoc with the technologies we are increasing reliant upon."

-- From Victoria University of Wellington Alumni News https://www.victoria.ac.nz/news/2017/10/solar-storms-and-aucklands-damaged-fuel-pipeline

Professor Rodger was after-dinner speaker at the RASNZ's Conference in Dunedin last May.

11. NZ's Stargazing Places Reviewed

It was as if a great celestial Bake Off was in action. Handfuls of sugar spilt across the sky and the faint floury stain of the Milky Way scattered overhead. With my neck craned all the way back, I felt dizzy trying to take in the immensity of it all. 'Here, the stars are so bright you can read the newspaper at night," laughs Hilde Hoven, one of the residents on New Zealand's Great Barrier Island.

In August of this year, Great Barrier - a 30-minute flight north-east of Auckland - was the first island in the world to be designated a Dark Sky Sanctuary. It's the third site in the world after the Cosmic Campground in the US state of New Mexico and the Gabriela Mistral Dark Sky Sanctuary, the site of Chile's government observatory.

This island of steep forested hills, wetlands and sweeping white-sand bays is completely off grid. All the residents are responsible for supplying their own power through solar, wind or gas. There are no billboards or street lights. And the complete lack of light pollution makes for a very sparkly stratosphere.

Typically, tourists come here to fish, hike and swap fast-paced city life for something slower. But come winter, visitor numbers drop from 12,000 to 2,500 and a solution was vital to support the island's 900 residents. It seems the starry solution was staring them right in the face and local residents Gendie and Richard Somerville-Ryan decided to apply for Dark Sky status.

Working with Auckland astronomer Nalayini Davies, they took readings all over the island one clear crisp night and sent the results off to the International Dark-Sky Association (IDA) for review. We thought we'd be a Reserve, but when the results came back they said, "You're not a Reserve" and we were really disappointed! They said, 'Your readings are technically darker than instruments should be able to measure - you have a very dark sky indeed!' grinned Gendie. 'What's strange is the darkest readings came on the west coast, closest to Auckland, which proves their light dome doesn't touch us. If it was too bright you wouldn't see Venus on the horizon.

Sanctuary rules are stricter than those of a Reserve because they have to be situated in a very remote location, promote long-term conservation and above all prove a night-sky brightness routinely equal to or darker than 21.5 mpsa (magnitudes per square arc second). Great Barrier Island has an mpsa of 21.97.

The effect has been immediate. After attending an intensive weekend training course - run by John Drummond, President of the Royal Astronomical Society of New Zealand - to become Dark Sky Ambassadors, Hilde (originally a translator) banded together with two other locals - Orla Cumisky (who works at the pub) and Deborah Kilgallon (a full-time mum) - to found Good Heavens and they now offer private stargazing experiences, starlit dinners with a gourmet chef and, on set dates, stargazing on the local beaches.

Hilde had their 8-inch Dobsonian telescope trained at the sky. 'OK, no peeking at your mobile phones - the white light destroys your night vision and it'll take 10 minutes for your eyes to adjust again,? she said, as we snuggled into beanbags positioned on the terrace of the hilltop Trillium Lodge. She beamed a green laser to point out the constellations of Sagittarius, Capricorn and Scorpio. 'In New Zealand, the scorpion's tail is known as Maui's Fishhook. Legend has it Maui [the Polynesian demigod] went fishing on his canoe one day and cast his hook into the ocean. As he hauled it in, many rocks appeared. He kept pulling and pulling until Aotearoa [New Zealand] appeared.

Next, the telescope was tilted towards Jupiter to see its moons, then Saturn to spy on its icy rings. But best of all were the constellations that are never visible in the northern hemisphere, such as the Southern Cross and the Magellanic Clouds - dwarf galaxies orbiting the Milky Way. And the new ways of seeing the familiar, such as Matariki - the Maori name for the Pleiades star cluster. Its appearance signals the start of the Maori New Year, but we know it as the Seven Sisters not far from Orion's feet.

I was eager for more, so flew down to South Island - home to Aoraki Mackenzie International Dark Sky Reserve, established in 2012. One of eight reserves in the world, it includes the Mount John Observatory where travellers can use the most-powerful telescopes in the country to peer into deep space. But I wanted something more intimate.

Luke and Kaye Paardekooper run Mount Cook Lakeside Retreat on the shores of Lake Pukaki inside the reserve. Having hosted the likes of Oprah Winfrey, film director James Cameron and NASA planet-hunter Natalie Batalha, they're well set up to offer luxury. Their private villa has uninterrupted views of the lake and an outdoor hot tub bubbling away at all times.

'Choose any bottle you like from the wine cellar, and then after dinner [a three-course affair prepared by chef Luke Mathewson] we'll head over to the observatory for a spot of stargazing,' said Luke. Sadly, halfway through dinner, dark clouds rolled in, obscuring the skies.

'It's best to visit in winter when the angles of the Earth allow you to see the full spread of the Milky Way - plus you don't have to stay up too late for it to get dark,' said Kaye, who is on the local Dark Sky board. 'Otherwise, time it for when the moon is new; visit when it's full and the dark sky will be outshone.'

Tucking in to dessert, I asked the awkward question: 'Will there be competition with Great Barrier Island now?' She shook her head. 'No, the more people talking about dark skies the better - it's not all about tourism, it just as much about conservation.'

One place taking conservation seriously is Skyscape, a new stargazing glasshouse that's just won a Qualmark Environmental Gold Award (handed out to just nine per cent of New Zealand properties). Lying in the southwest corner of the reserve, this solar-powered, one-room hideaway is tucked, hobbit-style, into the hillside. Its grass roof makes it impossible to pick out amid the tussock-laden landscape.

The brainchild of Bevan and Bridget Newland, Skyscape is set within the 6,000-acre Omahau Hill merino sheep station. Farm tours are offered, but mostly you're left in seclusion to soak up the snow-capped Two Thumb and Ben Ohau ranges rolled out before you. Days are spent sipping fine wine, spotting Marcus, the local highland bull, watching Australasian hawks hunting rabbits and paradise ducks that 'sound like fighter jets when they're landing,' according to Bevan. There's not another building in sight. Come nightfall, you can roll back the retractable sun blind, pull out the star chart and binoculars, and set to finding celestial bodies.

'There is Wi-Fi, but we tell people to turn it off. Skyscape is about totally switching off,' says Bevan. With a reported 99 per cent of Americans and Europeans no longer able to see the Milky Way due to light pollution, it's time to head south. Move over Hollywood, there's a new star in town.

-- See Emma Thomson's complete article at http://www.telegraph.co.uk/travel/destinations/oceania/new-zealand/articles/stargazing-in-new-zealand/ Thanks to John Hearnshaw for passing on the link.

12. Surprising Science from Cassini's Grand Finale

You'd think scientists would have Saturn all figured out after watching it up close for 13 years. They don't.

When NASA's Cassini spacecraft eased into orbit around Saturn in July 2004, its "to-do" list spanned every aspect of the Saturn system. Yet some of the mission's most memorable moments were close encounters with the planet's vast system of moons - from a single brush with two-faced Iapetus to 127 close flybys of huge, murky Titan (which included delivering the European Space Agency's Huygens lander).

But during the spacecraft's last four months in residence, the scientific focus was almost exclusively on Saturn itself and the majestic, dramatic, complex ring system that surrounds it. This "grand finale" carried Cassini on 20 orbits that skimmed just outside the main ring system and 22 that threaded a corridor between the planet and the vestiges of its innermost ring.

During a meeting of the American Astronomical Society's Division for Planetary Sciences, held in mid-October in Provo, Utah, a parade of Cassini scientists offered some of the insights they gained during this unprecedented scrutiny.

The final orbits sent the spacecraft dashing at 35 km/s north to south through a planet-ring gap about 2,400 km wide between the planet and the rings. But this region isn't truly empty - Cassini got a chance to directly sample the hydrogen and other compounds present in Saturn's uppermost atmosphere.

It's those "other compounds" that have planetary scientists scrambling for explanations. In theory, material is leaking from the innermost threads of the ring and drifting toward the planet, and generally the rings consist almost entirely of water ice. But investigator Mark Perry (Johns Hopkins University's Applied Physics Laboratory) reports that Cassini's Ion and Neutral Mass Spectrometer (INMS) found surprisingly little water in the planet-ring gap. That's partly due to water's tendency to stick to the tubing inside the INMS, Perry explains.

Instead, the mass spectrometer swept up many heavier compounds that haven't yet been identified. For example, a peak with an atomic weight of 16 is most likely methane (CH4), a gas that shouldn't be percolating up from the atmosphere and would be chemically out of place in the water-ice rings. Another peak at 28 could be carbon monoxide (CO) or molecular fragments of carbon-bearing dust particles. Confirming either of these will take more modelling to explain.

The close passes also allowed dynamicists to use tiny changes in Cassini's velocity to probe the planet's gravity field. As Michele Dougherty (Imperial College London) noted, this analysis is just getting started - but already it's raising questions about the state of Saturn's deep interior. One key question is whether the core is a distinct rocky mass or something more like the "fuzzy" dispersed core that Jupiter seems to have.

Meanwhile, Dougherty reports, Cassini got its best-ever chance to measure Saturn's magnetism. Earlier results had shown that the magnetic field was aligned closely with Saturn's spin axis, a unique arrangement in the solar system. But the close-in measurements now show that the axial alignment is incredibly close - to within about 0.06°. Saturn's magnetic dynamo likely occurs in a layer of metallic hydrogen deep inside the planet, but dynamo theory requires a tilt to generate a magnetic field.

"It's almost as if you can use the magnetic field to see inside Saturn itself," she notes, adding that the situation "must be more involved than we thought." She expects more clarity to emerge in a few months, after data from all the Grand Finale orbits have been analysed.

Cassini's close-in flybys also gave mission scientists a chance to examine the rings in extreme detail. They'd gotten one other opportunity like this - when the spacecraft passed very close to the planet during its arrival in 2004. But the final orbits provided a chance to re-examine some curiosities more intensively.

Matthew Tiscareno (SETI Institute) delved into three of these at the meeting. He described new views of clumpy structure in the main rings (dubbed "straw") that Cassini had seen earlier. Tiscareno can't yet explain how or why this occurs - the higher-quality images show that the clumpiness doesn't correlate with the pattern of rings or with sets of gravitationally induced waves found in them.

Other ring oddities, known as "propellers," are local disturbances in the myriad particles created by embedded but unseen bodies that range in size from 100 meters to 1 km across. Swarms of these features cluster in A ring - many small ones lie in the middle of the A ring, while the largest are found in the outer A ring. Tiscareno explained that some propellers have been tracked throughout Cassini's mission, and the final images should allow him and others to deduce not only the embedded moons' masses but also the sizes and distribution of ring particles sweeping by them.

Meanwhile, the ring system presents a huge yet delicate target for chunks of interplanetary debris up to a few meters across. When these strike the rings they create brief clouds of disrupted particles, and new images show lots of these splats. Tiscareno reports that colour information in the Cassini images should give mission scientists a handle on the composition of the colliding objects.

As with any good space mission, Cassini has raised some important new questions. For example, because of the near-identical alignment of Saturn's magnetic and rotation axes, scientists have struggled to determine just how fast the planet spins. We can see the motions of its clouds, but the rotation rate of its deep interior is still uncertain.

Another question is whether Cassini's Grand Finale observations can pin down the total mass of Saturn's rings - critical to models of how and when they formed. Project scientist Linda Spilker (Jet Propulsion Laboratory) hinted that, based on the analysis so far, that mass might be less than expected. But, as with all of these preliminary results, the final answer is still months away.

-- See Kelly Beatty's original article with images and links at http://www.skyandtelescope.com/astronomy-news/surprising-science-from-cassinis-grand-finale/

13. How to Join the RASNZ

RASNZ membership is open to all individuals with an interest in astronomy in New Zealand. Information about the society and its objects can be found at http://rasnz.org.nz/rasnz/membership-benefits A membership form can be either obtained from This email address is being protected from spambots. You need JavaScript enabled to view it. or by completing the online application form found at http://rasnz.org.nz/rasnz/membership-application Basic membership for the 2017 year starts at $40 for an ordinary member, which includes an electronic subscription to our journal 'Southern Stars'.

14. Email Address Changes, Please

Anyone with these email addresses will need to advise us of a new one: clear.net.nz es.co.nz ihug.co.nz paradise.net.nz pcconnect.co.nz quik.co.nz vodafone.co.nz wave.co.nz

Please send address changes to <This email address is being protected from spambots. You need JavaScript enabled to view it.> . Thanks to those who have already done so.

15. Next Newsletter December 16

The December Newsletter will be circulated on or before December 16th.

16. Quotes

"I have yet to see any problem, however complicated, which, when looked at in the right way did not become still more complicated." -- Poul Anderson.

"Good judgement comes from experience, and often experience comes from bad judgement." -- Rita May Brown.

Newsletter editor:

Alan Gilmore Phone: 03 680 6817
P.O. Box 57 Email: This email address is being protected from spambots. You need JavaScript enabled to view it.
Lake Tekapo 7945
New Zealand

RASNZ Electronic Newsletter December 2017

The RASNZ Email newsletter is distributed by email on or near the 20th of each month. If you would like to be on the circulation list This email address is being protected from spambots. You need JavaScript enabled to view it. for a copy. The latest issue is below.

Email Newsletter Number 204

Affiliated Societies are welcome to reproduce any item in this email newsletter or on the RASNZ website http://www.rasnz.org.nz/ in their own newsletters provided an acknowledgement of the source is also included.

Contents

1. More on the Interstellar Asteroid
2. Upcoming Astronomy Camps, Star Parties
3. RASNZ Administrative Deadlines
4. Central Star Party January 18-23
5. Back Issues of Southern Stars Wanted
6. BAA Membership Search
7. Impact of Blue Light LEDs
8. The Solar System in January
9. Cricket Thermometer
10. Antares Imaged
11. Why is Earth Magnetized and Venus Not?
12. Bird Migration Affected by Bright Urban Light
13. LIGO Sees Smallest Black Hole Binary Yet
14. "Universe - Exploring the Astronomical World"
15. Mt John History Price Reduced
16. How to Join the RASNZ
17. Kingdon-Tomlinson Fund
18. Quotes

1. More on the Interstellar Asteroid

For the first time ever astronomers have studied an asteroid that has entered the Solar System from interstellar space. Observations from many observatories around the world show that this unique object was traveling through space for millions of years before its chance encounter with our star system. It appears to be a dark, reddish, highly-elongated rocky or high-metal-content object. The new results appeared in the journal Nature on 20 November 2017.

Although originally classified as a comet, observations soon revealed no signs of cometary activity after it passed closest to the Sun in September 2017. The object was reclassified as an interstellar asteroid 1I/2017 U1 and named `Oumuamua. Note that the character before the O is an okina. So the name should sound like H O u mu a mu a. The prefix 1I is a new designation for interstellar objects.

Combining the images from many large telescopes, the team of astronomers led by Karen Meech (Institute for Astronomy, Hawai`i, USA) found that `Oumuamua varies dramatically in brightness by a factor of ten as it spins on its axis every 7.3 hours.

Karen Meech explains the significance: “This unusually large variation in brightness means that the object is highly elongated: about ten times as long as it is wide, with a complex, convoluted shape. We also found that it has a dark red colour, similar to objects in the outer Solar System, and confirmed that it is completely inert, without the faintest hint of dust around it.”

These properties suggest that `Oumuamua is dense, possibly rocky or with high metal content, lacks significant amounts of water or ice, and that its surface is now dark and reddened due to the effects of irradiation from cosmic rays over millions of years. It is estimated to be at least 400 metres long.

Preliminary orbital calculations suggested that the object had come from the approximate direction of the bright star Vega, in the northern constellation of Lyra. However, even travelling at a breakneck speed of about 95 000 kilometres/hour, it took so long for the interstellar object to make the journey to our Solar System that Vega was not near that position when the asteroid was there about 300 000 years ago. `Oumuamua May well have been wandering through the Milky Way, unattached to any star system, for hundreds of millions of years before its chance encounter with the Solar System.

Astronomers estimate that an interstellar asteroid similar to `Oumuamua passes through the inner Solar System about once per year, but they are faint and hard to spot so have been missed until now. It is only recently that survey telescopes, such as Pan-STARRS, are powerful enough to have a chance to discover them.

-- Extracted from European Southern Observatory press release http://www.eso.org/public/unitedkingdom/news/eso1737/ which also contains links to graphics and videos.

For technical details see the paper by Meech et al at https://www.eso.org/public/archives/releases/sciencepapers/eso1737/eso1737a.pdf

2. Upcoming Astronomy Camps, Star Parties

Central Star Party – Tuki Tuki Valley, Hawkes Bay. Thursday January 18th – Tuesday 23rd. See Item 4 below.

Star Date – Stonehenge Aotearoa, Wairarapa. Friday January 19 - Sunday 21. For details see http://www.astronomynz.org/
Star Date South Island – Stavely. Friday 16th – Monday 19th February 2018. See - http://www.treesandstars.com/Stardate

3. RASNZ Administrative Deadlines

February 3 is the deadline for the following:

  • RASNZ Fellow nominations - RASNZ Rule 19
  • RASNZ Honorary Members nominations - RASNZ Rule 11
  • RASNZ Murray Geddes Prize nominations - RASNZ By-Law G5
  • Nominations of RASNZ Officers for 2018-20 - RASNZ Rule 74
  • Earth & Sky Bright Star Award - RASNZ By-Laws K
  • Feb 15 RASNZ Section and Group reports due to the Secretary - RASNZ By-Law F14
  • Mar 15 SWAPA applications deadline (for high school students) - http://www.rasnz.org.nz

-- From Keeping in Touch #24. 18th November 2017

4. Central Star Party January 18-23

Central Star Party has been established to hold annual star parties in the central North Island for the benefit of the astronomical community of the North Island of New Zealand. The goal of the organisers is to provide a fun social astronomical gathering laced with talks and activities. More info can be found at www.censtar.party.

The second Central Star Party is Thursday 18th to Tuesday 23rd January 2018 and will be held at the Tuki Tuki Camp site in the Hawkes Bay. This is the site of many previous star parties. The site is complete now, and there is a brand new hall, with two additional meeting rooms for alternate meetings, a new kitchen and three new dormitories. Accommodation is tenting, staying in the dormitories or using one of the six powered caravan sites.

Last year's Central Star Party was a huge success with over 70 people attending and enjoying a great programme of presentations as well as a trip to the local observatory, sausage sizzles, entertainment as well as fish and chip dinners delivered to the camp. We also had sponsorship from a number of organisations including Astronz who donated a pair of binoculars (amongst other things) for a raffle. This year is shaping up to be even better, registrations are open now at www.censtar.party . Put the dates aside - this year should be a cracker!

-- Steve Lang and Gary Sparks

5. Back Issues of Southern Stars Wanted

Leonard Matula, a US collector of astronomical publications would appreciate the following editions to fill gaps in his collection:

  • Volume 55 (2016) number 1,
  • Volume 50 (2011) numbers 2, 3 and 4
  • Volumes 1 to 39, that is, all or any of the smaller A5 size.

If anyone can help, please send them to Bob Evans (address below) and he will pass them on. Bob's postal address: 15 Taiepa Road, Otatara, RD9, Invercargill 9879. Email This email address is being protected from spambots. You need JavaScript enabled to view it.; .

6. BAA Membership Search

Anthony Kinder writes: I am currently researching the membership of the British Astronomical Association (BAA) since it was founded in 1890. Included in this is any and all information I am able to obtain about the person concerned. There are a number of New Zealanders who were members (e.g. Leslie J. Comrie, John Grigg). I would be interested in hearing from any RASNZ member who is or was in the past (or even considering joining in the future) a member of the BAA.

Send replies to Anthony at This email address is being protected from spambots. You need JavaScript enabled to view it.;

7. Impact of Blue Light LEDs

The Royal Society of New Zealand has started developing expert advice to summarise the latest evidence on the impact of blue light wavelengths from LEDs. This could cover issues such as the impacts of: • LED screens and lighting on sleep patterns • LED street lighting on the nocturnal environment • blue wavelength light pollution on New Zealand's astronomy. For further information contact Dr Marc Rands This email address is being protected from spambots. You need JavaScript enabled to view it.;. https://royalsociety.org.nz/what-we-do/our-expert-advice/our-expert-advice-under-development/impacts-of-blue-light/

-- Forwarded by Steve Butler

8. The Solar System in January

Dates and times shown are NZDT (UT + 13 hours) unless otherwise stated.

Sunrise, Sunset and Twilight Times in November

Times are for Wellington. They will vary by a few minutes elsewhere in NZ.

             January  1  NZDT          January 31  NZDT
     SUN:  rise 5.48am, set 8.59pm    rise 5.47am, set 8.59pm
  Twilights    morning     evening        morning     evening
  Civil:    starts 5.17am, ends   9.31pm   starts 5.54am, ends  9.14pm
  Nautical: starts 4.34am, ends  10.14pm   starts 5.16am, ends  9.52pm
  Astro:    starts 3.43am, ends  11.04pm   starts 3.42am, ends 10.34pm

The Earth is at perihelion, its closest to the Sun for the year, on January 3. Earth will then be 147 million kilometres, 0.983 AU, from the Sun

January Phases of the Moon (times NZDT, as shown by GUIDE)

          Full moon:     January  2 at  3.24pm (02:24 UT)
  Last quarter   January  9 at 11.25am (Jan  8, 22:25 UT)
  New moon:      January 17 at  3.17pm (02:17 UT)
  First quarter: January 25 at 11.20am (Jan 24, 22:20 UT)
  Full moon     February  1 at  2.27am (Jan 31, 13:27 UT)

A total eclipse of the moon, fully visible from NZ, takes place on the night of January 31/February 1. The eclipse will be total between 1:52 a.m. and 3:08 a.m. on the morning of Feb 1. Further details can be found on the RASNZ web site.

The Planets in January 2018

The five inner planets are morning objects throughout January, with the exception of Venus which becomes an evening object after conjunction with the Sun on the 9th. Mercury and Venus will be difficult objects to view all month, with Saturn coming into view in the morning sky during January.

Mars and Jupiter will be the most interesting planets to watch. They form a close pair early in the month.

MARS and JUPITER start January as a pair in the morning sky. On the 1st they will be 3° apart with Mars to the upper left of Jupiter. They are closest on the mornings of January 7 and 8. On the 7th Mars will be some 17 arc-minutes above Jupiter, the following morning Mars will be level with and to the right of Jupiter, the two now 22 arc-minutes apart. Mars will, of course, be much fainter than Jupiter, by over 3 magnitudes. Look for the pair of planets an hour before sunrise at an elevation of 30° almost due east.

During the rest of January Mars will steadily pull away from the slower moving Jupiter, by the end of the month they will be about 12° apart. Both will be in Libra all month, although on the 31st Mars will be poised to move into Scorpius with Antares 9° to its right.

On the 12th the crescent moon will be 6° below the planets as seen about 5 am.

MERCURY is in the morning sky. On January 1 it rises almost 90 minutes before the Sun. Forty-five minutes before sunrise the planet, magnitude -0.4, will be a mere 6° up, with the Sun 8° below the horizon. During the month the elongation of Mercury from the Sun reduces, so it will get even lower in the morning twilight.

SATURN, also in the morning sky, will emerge from the Sun during January. On the 1st it will rise about 40 minutes before the Sun, an interval increasing to almost 3 hours by the end of the month.

Similar to Mars and Jupiter, Mercury will move past Saturn during January. On the 13th Mercury will be just under a degree above Saturn, the following morning it will nearly 2° to the lower right of Saturn. Also the moon, as a thin crescent, will then be 5.5° to the left of Saturn. All will be difficult to see, some 7 to 8° up 45 minutes before sunrise, Mercury a little brighter than Saturn

VENUS rises only 10 minutes before the Sun on January 1. By the 9th it is at superior conjunction. At conjunction Venus will be half a degree south of the Sun but 109 million km beyond it. Two hours after Venus is at conjunction, Pluto is also at conjunction. Following their conjunctions Venus will become an evening object while Pluto becomes a morning object.

By the end of January, Venus will be setting only 25 minutes after the Sun, so it will remain a difficult object all month.

Outer Planets

URANUS is an evening object in Pisces during January. It is best placed in the evening sky as soon as it is dark. Uranus will set at 12.45 am by the end of the month.

NEPTUNE is an early evening object in January. It sets at midnight on the 1st and 10 pm, before the end of astronomical twilight, on the 31st. The planet is in Aquarius at magnitude 7.9.

PLUTO, is at conjunction with the Sun on January 9.

Brightest Minor Planets

(1) CERES is a morning object, at first in Leo then in Cancer from the 19th. During January it brightens from magnitude 7.5 to 6.9.

(2) PALLAS is an evening object with magnitude dimming slightly from 8.7 to 9.0 during January. It starts in Fornax, crosses a corner of Cetus between January 13 and 22, to end the month in Eridanus.

(4) VESTA starts January in Libra, crosses a narrow part of Scorpius between the 18th and 29th and then moves into Ophiuchus. Its magnitude changes little, from 7.9 to 7.8.

(7) IRIS is an evening object in Aries, dimming from magnitude 8.6 to 9.3 during the month. By the end of January it sets just after midnight.

(8) FLORA is in Gemini all month, starting January at magnitude 8.2. It is at opposition on the 2nd when it will be 155 million km from the Earth, 1.034 AU. After opposition it becomes an evening object but dims to magnitude 9.2 by the end of January.

(20) MASSALIA is in Taurus during January. It fades from magnitude 8.9 to 9.6 during the month.

-- Brian Loader

9. Cricket Thermometer

Last November saw the anniversary of the birth, in Norwich, Connecticut on 10 Nov 1837, of the American physicist and inventor Amos Emerson Dolbear. A graduate of Ohio Wesleyan University, he is not particularly associated with astronomy, other than the fact that in 1897 he published an article ‘The Cricket as a Thermometer’ that noted the correlation between the ambient temperature and the rate at which crickets chirp. The formula expressed in that article became known as Dolbear's Law and was in fact mentioned in the May 1946 issue of Sky and Telescope in the monthly Astronomical Anecdotes (fascinating pieces of astronomical trivia which were compiled and written by Roy Kenneth Marshall and featured in the magazine between 1941 and 1946).

Apparently, if an observer inside an observatory dome wanted to know the ambient temperature (and in the fortunate event that a cricket happened to be inside the dome at the same time) the astronomer in question would be able to count the number of times the cricket 'chirped' over a period of 15 seconds and then add that value to 40 to give the temperature in Fahrenheit! This method is certainly more elaborate, and perhaps a lot more fun, than simply using a thermometer, although I am unable to vouch for its accuracy…

-- via Brian Jones forwarded by Phil Yock.

10. Antares Imaged

Using ESO’s Very Large Telescope Interferometer astronomers have constructed the most detailed image ever of a star — the red supergiant star Antares. They have also made the first map of the velocities of material in the atmosphere of a star other than the Sun, revealing unexpected turbulence in Antares’s huge extended atmosphere. The results were published in the journal Nature in August.

To the unaided eye the famous, bright star Antares shines with a strong red tint in the heart of the constellation of Scorpius (The Scorpion). It is a huge and comparatively cool red supergiant star in the late stages of its life, on the way to becoming a supernova.

A team of astronomers, led by Keiichi Ohnaka, of the Universidad Católica del Norte in Chile, has now used ESO’s Very Large Telescope Interferometer (VLTI) at the Paranal Observatory in Chile to map Antares’s surface and to measure the motions of the surface material. This is the best image of the surface and atmosphere of any star other than the Sun.

The VLTI is a unique facility that can combine the light from up to four telescopes, either the 8.2-metre Unit Telescopes, or the smaller Auxiliary Telescopes, to create a virtual telescope equivalent to a single mirror up to 200 metres across. This allows it to resolve fine details far beyond what can be seen with a single telescope alone.

“How stars like Antares lose mass so quickly in the final phase of their evolution has been a problem for over half a century,” said Keiichi Ohnaka, who is also the lead author of the paper. “The VLTI is the only facility that can directly measure the gas motions in the extended atmosphere of Antares — a crucial step towards clarifying this problem. The next challenge is to identify what’s driving the turbulent motions.”

Using the new results the team has created the first two-dimensional velocity map of the atmosphere of a star other than the Sun. They did this using the VLTI with three of the Auxiliary Telescopes and an instrument called AMBER to make separate images of the surface of Antares over a small range of infrared wavelengths. The team then used these data to calculate the difference between the speed of the atmospheric gas at different positions on the star and the average speed over the entire star. This resulted in a map of the relative speed of the atmospheric gas across the entire disc of Antares — the first ever created for a star other than the Sun.

The astronomers found turbulent, low-density gas much further from the star than predicted, and concluded that the movement could not result from convection, that is, from large-scale movement of matter which transfers energy from the core to the outer atmosphere of many stars. They reason that a new, currently unknown, process May be needed to explain these movements in the extended atmospheres of red supergiants like Antares.

“In the future, this observing technique can be applied to different types of stars to study their surfaces and atmospheres in unprecedented detail. This has been limited to just the Sun up to now,” concludes Ohnaka. “Our work brings stellar astrophysics to a new dimension and opens an entirely new window to observe stars.”

---------- Antares is considered by astronomers to be a typical red supergiant. These huge dying stars are formed with between nine and 40 times the mass of the Sun. When a star becomes a red supergiant, its atmosphere extends outward so it becomes large and luminous, but low-density. Antares now has a mass about 12 times that of the Sun and a diameter about 700 times larger than the Sun’s. It is thought that it started life with a mass more like 15 times that of the Sun, and has shed three solar-masses of material during its life.

For images and links see https://www.eso.org/public/news/eso1726/

-- European Southern Observatory press release 1726, forwarded by Karen Pollard.

11. Why is Earth Magnetized and Venus Not?

A new analysis reveals that the gigantic impact that led to the Moon's formation might have also switched on Earth's magnetic field.

Based on their bulk density, Venus and Earth have cores that take up about half of their radius and roughly 15% of their volumes. Researchers don't know if Venus has a solid inner core, as Earth does.

Planetary scientists don't really know what to make of Venus. Although it's a near twin of Earth in size, mass, and overall rocky composition, the two are worlds apart (so to speak) in many ways. One obvious difference is our sister planet's dense, cloud-choked atmosphere. This enormous blanket of carbon dioxide has triggered a runaway greenhouse effect, trapping solar energy so well that the planet's surface temperature has rocketed to roughly 460°C.

Dig deeper, and the differences become even starker. Based on its density alone, Venus must have an iron-rich core that's at least partly molten — so why does it lack the kind of global magnetic field that Earth has? To generate a field, the liquid core needs to be in motion, and for a long time theorists suspected that the planet's glacially slow 243-day spin was inhibiting the necessary internal churning.

But that's not the cause, researchers say. "The generation of a global magnetic field requires core convection, which in turn requires extraction of heat from the core into the overlying mantle," explains Francis Nimmo (University of California, Los Angeles). Venus lacks any of the plate tectonism that's a hallmark of Earth — there's no rising and sinking of plates to carry heat from the deep interior in conveyor-belt fashion. So for the past two decades Nimmo and others have concluded that the mantle of Venus must be overly hot, and heat can't escape from the core fast enough to drive convection.

Now a new idea has emerged that attacks the problem from a wholly new angle. As Seth Jacobson (now at Northwestern University) and four colleagues detail in September's Earth and Planetary Science Letters, Earth and Venus might both have ended up without magnetic fields, save for one critical difference: The nearly assembled Earth endured a catastrophic collision with a Mars-size impactor — the one that led to the Moon's creation — and Venus did not.

Jacobson and his team simulated the gradual build-up of rocky planets like Venus and Earth from countless smaller planetesimals early in solar system history. As bigger and bigger chunks came together, whatever iron they delivered sank into the completely molten planets to form cores. At first the cores consisted almost completely of iron and nickel. But more core-forming metals arrived by way of impacts, and this dense matter sank through each planet's molten mantle — picking up lighter elements (oxygen, silicon, and sulphur) along the way.

Over time these hot, molten cores developed several stable layers (maybe as many as 10) of differing compositions. "In effect," the team explains, "they create an onion-like shell structure within the core, where convective mixing eventually homogenizes the fluids within each shell but prevents homogenization between shells." Heat would still bleed out into the mantle but only slowly, via conduction from one layer to the next. Such a stratified core would lack the wholesale circulation necessary for a dynamo, so there'd be no magnetic field. This might have been the fate of Venus.

On Earth, meanwhile, the Moon-forming impact affected our planet literally to its core, creating turbulent mixing that disrupted any compositional layering and creating the same mix of elements throughout. With this kind of homogeneity, the core started convecting as a whole and drove heat readily into the mantle. From there, plate tectonism took over and delivered that heat to the surface. The churning core became the dynamo that created our planet's strong, global magnetic field.

What's not yet clear is how stable these compositional layers would really be. The next step, Jacobson says, is to grind through more rigorous numerical modelling of the fluid dynamics involved.

The researchers note that Venus certainly endured its share of big impacts as it grew in size and mass. But apparently none of them hit planet hard enough — or late enough — to disrupt the compositional layering that had already settled out in its core. By contrast, the team concludes, "Earth was struck violently at the end of its growth, simultaneously creating its Moon and homogenizing its core." If they're right, then the divergence of Earth and Venus becomes a classic story of planetary "haves" and "have nots."

-- Article by Kelly Beatty with images and diagrams at http://www.skyandtelescope.com/astronomy-news/why-is-earth-magnetized-and-venus-not-magnetized/

12. Bird Migration Affected by Bright Urban Light

Tribute in Light in New York City projects two beams of light into the sky as an annual memorial to the victims of 9/11. The tribute also occurs during peak bird migration in North America. Recognizing a unique opportunity, a team of scientists and volunteers gathered each year at the memorial on September 11 since 2005 to study the effects of high intensity lights on bird migration.

In 2008, the team began using radar and acoustic sensors to monitor bird activity in and around the site. On the study night in 2010, a particularly high density of birds seemed to be trapped within the perimeter of the illumination. The team convinced the memorial managers to turn the lights off for 20 minutes and the birds quickly dispersed.

In the years since, memorial operators have continued to shut the lights off when high counts of birds were observed. This created an opportunity to study the difference between having the lights on and off at the site, so the scientists compiled data they had collected between 2008 and 2016 to analyse the contrast. The study consists of data from 7 non-consecutive years, excluding data from 2 years when it was raining.

According to the recently published study, “High-intensity urban light installation dramatically alters nocturnal bird migration,” the lights at the tribute were shut down for about 20 minutes at a time, for a total of 22 times on the nights of the study between 2010 and 2017. The contrast between the high-intensity light and no light allowed the researchers “to directly contrast birds’ behaviours during adjacent dark and illuminated periods.”

The findings from the study confirm what IDA has long thought to be the case for such high-intensity outdoor light installations. It has been previously documented that birds are attracted to bright lights. High-intensity artificial lights along migration routes attract and disorient birds, disrupting their progress.

This is exactly what the researchers found at the Tribute in Light. They measured more than 20 times the density of birds near the memorial than in surrounding areas. The birds spent long periods circling inside of the cone of illumination and they vocalized frequently. This meant that they were using precious energy, but not making any progress on their migration routes. Some died of exhaustion, while others collided with nearby buildings.

The Tribute in Light is a unique installation that beams light up to four miles above the ground, yet some of the study findings can be applied to all artificial light at night (ALAN). For instance, one of the key observations of the study is that “short-term removal of ALAN eliminated its disruptive effects almost instantaneously.”

An article on the Discover Magazine blog noted, “Beyond the unique natural experiment, the researchers also say the Tribute in Light offers a lesson in addressing the larger problem of light pollution. If conservationists and memorial organizers can work together at such an emotionally charged site, then other cities should be able to find solutions.” IDA hopes that the study will be useful to communities lobbying for the prevention of light pollution.

While there is much more to learn about the effects of artificial light at night, the International Dark-Sky Association appreciates that this study proves that limiting the duration of lights has a demonstrable benefit. Turning the lights off does what we think it does, which is protecting the night sky for birds and other nocturnal creatures.

-- Article by Meg Schader of the International Dark-Sky Association at http://www.darksky.org/bird-migration-dramatically-altered-by-high-intensity-urban-light-installation/

13. LIGO Sees Smallest Black Hole Binary Yet

LIGO has detected another black hole merger, raising the tally to five. On November 15th astronomers announced the detection of their sixth gravitational-wave discovery, which is the fifth from the merger of two black holes. The event, GW170608, came from the union of the smallest black holes scientists have yet “seen” using this technique. The waves hit LIGO at 02:01:16 Universal Time on June 8th, during the project’s second observing run (November 30th to August 25th).

Based on the signal’s characteristics, the two teams infer that the initial black holes were roughly 7 and 12 solar masses and created an 18-solar-mass black hole, radiating away a Sun’s worth of energy in gravitational waves. The merger happened more than a billion light-years away. With only two detectors, the team can only say that the signal came from somewhere in a huge, 520-square-degree swatch of sky in the Northern Hemisphere.

The spin of the final black hole is 69% of the maximum value it could be — once again matching the predicted 70% rate for black holes that have been created by the merger process. There’s also no sign that the two initial objects were wildly tilted in their orbit as they spiralled into each other.

The most interesting thing about this latest detection, however, is the black holes’ small sizes. They’re similar to those from LIGO’s second discovery, GW151226, which combined objects of about 8 and 14 solar masses to create a black hole of 21 Suns (the rest was radiated away). These initial masses are also similar to black holes discovered in binary systems with stars, which astronomers can find due to the X-ray glow of the gas the black holes are tearing from their stellar companions. This is exciting because of a tantalizing possibility: If the black holes discovered with LIGO and Virgo start falling into two distinct mass groups, then it’s possible that they’re made different ways. With enough black holes — and the teams say that they’ll need to find on the order of 100 — astronomers could start figuring out where each group comes from.

It's expected that increases in detector sensitivity in late 2018 will make detection of black hole binaries a routine occurrence.

Reference: The LIGO Scientific Collaboration and Virgo Collaboration. “GW170608: Observation of a 19-solar-mass Binary Black Hole Coalescence.” Posted to arXiv.org on November 15, 2017.

-- From the article by Camille M. Carlisle at http://www.skyandtelescope.com/astronomy-news/ligo-sees-smallest-black-hole-binary-yet-1611201723/

14. "Universe - Exploring the Astronomical World"

David Malin points out a new book "Universe - Exploring the Astronomical World". It contains 300 images covering ~15,000 years of studying the sky, chosen by artists with captions written by scientists.

ISBN 0714874612; publisher Phaidon Press. For details see http://tinyurl.com/y8wo4qvabut it's cheaper from Book Depository.

15. Mt John History Price Reduced

The Mt John history 'Mt John – The First 50 Years', a celebration of half a century of optical astronomy at the University of Canterbury by John Hearnshaw and Alan Gilmore, published in March 2015 is now selling for $20. It was $60. For details see http://www.cup.canterbury.ac.nz/catalogue/mt_john.shtml

16. How to Join the RASNZ

RASNZ membership is open to all individuals with an interest in astronomy in New Zealand. Information about the society and its objects can be found at http://rasnz.org.nz/rasnz/membership-benefits A membership form can be either obtained from This email address is being protected from spambots. You need JavaScript enabled to view it. or by completing the online application form found at http://rasnz.org.nz/rasnz/membership-application Basic membership for the 2017 year starts at $40 for an ordinary member, which includes an electronic subscription to our journal 'Southern Stars'.

17. Kingdon-Tomlinson Fund

The RASNZ is responsible for recommending to the trustees of the Kingdon Tomlinson Fund that grants be made for astronomical projects. The grants May be to any person or persons, or organisations, requiring funding for any projects or ventures that promote the progress of astronomy in New Zealand. Applications are now invited for grants from the Kingdon-Tomlinson Fund. The application should reach the Secretary by 1 May 2016. There will be a secondary round of applications later in the year. Full details are set down in the RASNZ By-Laws, Section J.

For an application form contact the RASNZ Executive Secretary, This email address is being protected from spambots. You need JavaScript enabled to view it. Nichola van der Aa, 32A Louvain Street, Whakatane 3120.

18. Quotes

"The science of Astronomy is so rapidly progressive, that to keep the public advised of its advances new works are required almost every year." -- From the preface to 'Popular Astronomy and the Orbs of Heaven' by O. M. Mitchell, January 1860.

"Somehow the word 'quantum' manages to sound simultaneously mysterious and scientific, and so people attach it to things that they want to sound simultaneously mysterious and scientific, like diets and the power of positive thinking, or even theology." - Michelle Francl-Donnay.

---------- Season's greetings to all our readers and best wishes for 2018. -- Ed

Newsletter editor:

Alan Gilmore Phone: 03 680 6817
P.O. Box 57 Email: This email address is being protected from spambots. You need JavaScript enabled to view it.
Lake Tekapo 7945
New Zealand

RASNZ Electronic Newsletter September 2017

The RASNZ Email newsletter is distributed by email on or near the 20th of each month. If you would like to be on the circulation list This email address is being protected from spambots. You need JavaScript enabled to view it. for a copy. The latest issue is below.

Email Newsletter Number 201

Affiliated Societies are welcome to reproduce any item in this email newsletter or on the RASNZ website http://www.rasnz.org.nz/ in their own newsletters provided an acknowledgement of the source is also included.

Contents

1. Beatrice Hill Tinsley 2017 Lecture Tour
2. 2017 Burbidge Dinner - Auckland
3. Exploring Mars with 150,000 Earthlings - Wellington & Auckland
4. Third International Starlight Festival, 13-15 October
5. Great Barrier Island Now a Dark Sky Sanctuary
6. The Solar System in October
7. Starpath Game Wins Future Transport Competition
8. Variable Star News
9. New Supernova Analysis Reframes Dark Energy Debate
10. ASKAP Joins the Hunt for Fast Radio Bursts
11. Future Star Encounters
12. How to Join the RASNZ
13. Quotes

1. Beatrice Hill Tinsley 2017 Lecture Tour

The RASNZ Lecture Trust Inc. is pleased to announce that the 2017 Beatrice Hill Tinsley Lecturer is Dr. Natalie Batalha. The lecture tour will be held during October and will include appearances at the Starlight Festival at Mt Cook village (13-15 October) and lectures at venues through the country. See places and times below.

Dr. Natalie Batalha is an astrophysicist at NASA Ames Research Center and the Mission Scientist for NASA's Kepler Mission. She has been involved with the Kepler Mission since the proposal stage and has contributed to many different aspects of the science, from studying the stars themselves to detecting and understanding the planets they harbour. She led the analysis that yielded the discovery in 2011 of Kepler-10b ? the mission's first confirmation of a rocky planet outside our solar system. Today, she leads the effort to understand planet populations in the galaxy based on Kepler discoveries. In 2011, Dr. Batalha was awarded a NASA Public Service Medal for her vision in communicating Kepler science to the public and for outstanding leadership in coordinating the Kepler Science Team. In 2015, she joined the leadership team of NASA's Nexus for Exoplanet System Science (NExSS). NExSS brings teams from multiple disciplines together to understand the diversity of worlds and will lead NASA's efforts to understand which are most likely to harbour life.

Dr. Batalha's Lecture Title and Synopsis A Planet for Goldilocks: The Search for Evidence of Life Beyond Earth

"Not too hot, not too cold" begins the prescription for a world that's just right for life as we know it. Finding evidence of life beyond Earth is one of the primary goals of science agencies around the world thanks in large part to NASA's Kepler Mission which launched in 2009 with the objective of finding Goldilocks planets orbiting other stars like our Sun. The space telescope opened our eyes to the terrestrial-sized planets that populate the galaxy as well as exotic worlds unlike anything that exists in the solar system. The mission ignited the search for life beyond earth via remote detection of atmospheric biosignatures on exoplanets. Most recently, our collective imagination was awakened by the discovery of Goldilocks worlds orbiting some of the nearest neighbours to the Sun, turning abstractions into destinations. Dr. Batalha will give an overview of the science legacy of the Kepler Mission and other key discoveries. She'll give a preview of what's to come by highlighting the missions soon to launch and those that are concepts taking shape on the drawing board.

Lecture venues and times

Auckland, Friday October 6, 7pm, Lecture theatre OGGB4, Level 0, Owen G Glenn Building, The University of Auckland, 12 Grafton Road. Register for this free event at nataliebatalha.eventbrite.co.nz

Whangarei October 7, 7:00pm, Tikipunga High School Hall. Admission: Adults $10, Child $5. Bookings: www.planets.nz

Gisborne October 9, 7:00pm, War Memorial Theatre, 159 Bright Street, Gisborne. Admission: Adult $10, Child $5 (under 15).

Palmerston North October 10, 7:30pm, Community Leisure Centre, Ferguson Street, Palmerston North. Gold coin admission.

Christchurch Wednesday October 11, 07:30 pm. Lecture Theatre A1, Canterbury University, Ilam, Christchurch. No admission charge.

Invercargill October 18, 7:30pm, The Ascot Park Hotel, Admission: Adult & S.I.T. Students $5.00, School Students $2.00.

Dunedin October 19, Hutton Theatre, Otago Museum at 5:30 pm. No admission charge.

-- Mostly from http://rasnz.org.nz/rasnz/beatrice-hill-tinsley-lectures

2. 2017 Burbidge Dinner - Auckland

Date: Saturday, 7th October 2017 Venue: Ellerslie Events Centre, Guineas 3 room Start Time: 7:00pm (doors open at 6:30pm)

Tickets: $65 pp. Includes a buffet dinner. Ticket can be booked:

  • by email at This email address is being protected from spambots. You need JavaScript enabled to view it.
  • by phone to Niven on 021 935 261 or Bill on 021 225 8175.

Our guest speaker this year is: Dr Meg Schwamb, Assistant Scientist at the Gemini Observatory's Northern Operations Center in Hilo, Hawai'i. Her talk will be:

Archaeology of the Outer Solar System

Pluto resides beyond Neptune orbiting in a sea of small icy bodies known as the Kuiper belt. These distant objects are truly the fossil relics left over after our Solar System's formation. Digging into the orbits, dynamics, and physical properties of these bodies, provides new insights and windows into the origins and past history of the outer Solar System. This includes hints of a possibly unseen planet, or an event long-since erased from the rest of the Solar System.

In this talk, we'll explore the changing views of the outer Solar System from the discoveries of ground-based surveys to the New Horizons fly-by of the Pluto System.

This talk will not be technical and is suitable for a general audience. Meg Schwamb is a planetary scientist and astronomer studying the bodies in our Solar System and beyond. She currently is an assistant scientist at the Gemini Observatory based in Hilo, Hawai'i. Meg's research focuses on how planets and their building blocks form and evolve, applying ground-based surveys to probe our Solar System's small body reservoirs. Later on this year, Meg will receive the Carl Sagan Medal for Excellence in Public Communication in Planetary Science from the American Astronomical Society's Division for Planetary Science.

As well as our guest speaker there will be the prize giving for the Astrophotography Competition including the Harry Williams Trophy for the supreme winner, and the Beaumont Writing Prize. A spectacular venue, great meal, cash bar and ample free parking.

-- Jonathan Green

3. Exploring Mars with 150,000 Earthlings - Wellington & Auckland

Astronz and the Wellington Astronomical Society are hosting a public talk by Meg Schwamb from the Gemini Observatory at 6:30pm on Tuesday 10th October. For venue details see the Wellington Astronomical Society's webpage or Facebook page

This talk will also be given in Auckland on 9th October as the Auckland Astronomical Society monthly meeting.

The Red Planet is a dynamic world. Mars' south pole is sculpted by the never-ending cycle of freezing and thawing of exposed carbon dioxide ice. In the summer, carbon dioxide jets loft dust and dirt through cracks in the thawing carbon dioxide ice sheet to the surface where winds blow the material into the hundreds of thousands of dark fans observed from orbit. This process is completely alien, with no Earthly counterpart. Understanding the direction, frequency, and appearance of these fans (a proxy for the jets) and how varying factors impact these properties, we can better understand the Martian climate and how it differs from Earth.

It is difficult if not impossible for computer algorithms to accurately identify individual fans. Computers just aren't good enough to do the required task, but the fans spotted for orbit are easily spotted by the human eye. I will talk about the Planet Four and Planet Four: Terrains projects and its on-going effort collaborating with over 150,000 people around the world through power of the Internet. Volunteers map the dark seasonal fans and other surface features carved during by the carbon dioxide gas jets. I will present the discoveries made by these citizen scientists and discuss how you can get involved in exploring Mars from the comfort of home.

See above, Item 2, for a synopsis on Meg Schwamb.

-- Thanks to Andrew Buckingham.

4. Third International Starlight Festival, 13-15 October

The Third International Starlight Festival will be held at the Hermitage, Mt Cook over three days in 2017, 13-15 October.

The Festival will celebrate the Aoraki Mackenzie International Dark Sky Reserve (www.darkskyreserve.org.nz) whose mission is to encourage and protect dark skies free of light pollution in the Mackenzie, and to promote star gazing and astro-tourism. We do this by organizing a Starlight Festival every second year for the benefit of the public and international tourists. Astro-tourism in the Mackenzie at Tekapo and Mt Cook is now one of New Zealand?s biggest tourist attractions, with about 200,000 people coming to Tekapo annually, many from Asia and Europe, to see the stars.

The 2017 Festival will be our third, after very successful events in 2013 in Tekapo and 2015 at Twizel. The Festival will be a mixture of events including lectures, workshops, exhibitions, videos and documentaries, planetarium shows and of course, star-gazing. We have engaged three world-class speakers to come to Mt Cook for the Festival. They are:

? Dr Natalie Batalha NASA Ames space scientist, Moffett Field (near San Francisco), California. (Time Magazine in April 2017 named her as one of the 100 most influential people on the planet). She will talk about ?A Planet for Goldilocks? and the search for habitable Earth-like planets ? Kevin Govender, Director of the Office of Astronomy for Development of the International Astronomical Union, based in Cape Town, South Africa. He will talk about ?Astronomy for Humankind?. ? Sze-leung Cheung, Director of the Office of Astronomy Outreach of the International Astronomical Union, based in Tokyo, Japan. He will talk about ?The threat of LEDs to astronomy and how to build a dark-sky-friendly future?.

All three are outstanding speakers, and Sze-leung Cheung is fluent in Chinese as well as English, so can give his talk in both languages to attract overseas tourists.

More details on the Third Starlight Festival and our keynote speakers are at www.starlightfestival.org.nz. On-line ticket sales will be available from mid-July. The website also has all accommodation options in and near Mt Cook.

Mark Gee from Wellington will show some of his stunning night-sky time-lapse animations and on the morning of Oct 14 will conduct an astro-photography workshop for everyone wanting to learn these techniques. Steve Chadwick from Palmerston North will show his amazing night sky animations and photography, as will also the renowned Fairlie and Tekapo astrophotographer, Fraser Gunn.

There is also an astro-photography exhibition with nine of New Zealand?s top astro-photographers exhibiting their images. The Festival features videos, exhibitions, workshops, planetarium shows and stargazing (at the new Mt Cook Observatory) over three days, 13-15 October.

-- John Hearnshaw, Chair, Aoraki Mackenzie International Dark Sky Reserve Board.

5. Great Barrier Island Now a Dark Sky Sanctuary

Great Barrier Island has become the world's first island to be recognised as a Dark Sky Sanctuary. On Saturday August 19 a quarter of the its 1000-strong population turned out to bask in the starry glow of a unique global status.

The outer Hauraki Gulf island - located 90 kilometres north-east of Auckland - has no mains electricity, and has now been recognised for its star-gazing credentials by the International Dark-Sky Association (IDA). Only two other locations in the world are considered Dark Sky Sanctuaries: Chile's Gabriela Mistral and the Cosmic Campground in the US state of New Mexico. Great Barrier stands out as the only such sanctuary to comprise an entire island.

Residents Gendie and Richard Somerville-Ryan worked with an Auckland astronomer to prove Great Barrier deserved its official accolade. "We had the right place for it, a remote, pristine environment that's off the grid. It was the right time for us to ensure we protected the dark sky, and we had the right people," Richard said.

Great Barrier Local Board Chair Izzy Fordham said Auckland-based astronomers brought over telescopes for the islanders to view. There was a long list of acknowledgements to those who helped the island's IDA application, Fordham said.

"We've had incredible support from the community along the way and so many others who have got behind this. "Sanctuary status is reserved for the most isolated, and dark locations in the word and this designation is specifically designed to increase awareness of fragile sites and promote their long-term conservation." Because of its relative isolation compared to the South Island's popular Tekapo star-gazing site, Great Barrier could benefit from "boutique style tourism" keeping its unspoilt environment, Fordham said.

Auckland Mayor Phil Goff and Great Barrier Island MP Nikki Kaye helped mark the occasion as around 250 residents celebrated at the Claris Sports Club. Goff said the islanders' "hard work has brought us together to celebrate a great moment in Auckland's history".

What makes for dark sky status? The International Dark-Sky Association (IDA) lays-out three criteria:

  • An area has to have "exceptional or distinguished quality of starry nights and a nocturnal environment that is protected for its scientific, natural, or educational value, its cultural heritage and/or public enjoyment".
  • Sanctuaries must typically be "situated in a very remote location with few (if any) nearby threats to the quality of its dark night skies and it does not otherwise meet the requirements for designation as a park or reserve".
  • A sanctuary's designation is "designed to increase awareness of these fragile sites and promote their long-term conservation".

-- Copied from Simon Maude's article on the Stuff website at https://www.stuff.co.nz/science/95959306/great-barrier-island-recognised-as-a-dark-sky-sanctuary

6. The Solar System in October

Sunrise, Sunset and Twilight Times in October

Times are for Wellington. They will vary by a few minutes elsewhere in NZ.

                    October  1  NZDT               October 31  NZST
       SUN: rise: 6.53am,  set: 7.28pm    rise:  6.06am,  set: 8.02pm
Twilights     morning       evening          morning       evening
Civil:    starts: 6.28am, ends: 7.54pm   starts: 5.48am, ends: 8.30pm
Nautical: starts: 5.55am, ends: 8.27pm   starts: 5.04am, ends: 9.07pm
Astro:    starts: 5.22am, ends: 9.01pm   starts: 4.25am, ends: 9.46pm

October Phases of the Moon (times NZST, as shown by GUIDE)

          Full moon:     October  6 at  9.40 am (Oct  5, 18:40 UT)
  Last quarter   October 13 at  1.26 am (Oct 12, 12:26 UT)
  New moon:      October 20 at  8.12 am (Oct 19, 19:12 UT)
  First quarter: October 28 at 11.22 am (Oct 27, 22:22 UT)

The Planets in October 2017

Four of the five naked eye planets will be close to the Sun during October. During the month Mercury reaches superior conjunction and Jupiter is at conjunction on the 27th. On the other hand Uranus is at opposition on the 20th. Saturn is the only naked eye planet readily visible - unless you can spot Uranus at magnitude 5.7.

MERCURY is at superior conjunction at the far side of the Sun on October 9, NZ time. Following conjunction the planet will become an evening object setting after the Sun. By the end of the month Mercury that will be an hour and a quarter later than the Sun. The planet, at magnitude -0.4, could just be visible some 45 minutes after sunset but very low at an altitude of 4.5° in a direction between midway between west and northwest.

VENUS is a very low morning object during October. On the 1st it rises 50 minutes before the Sun, by the 31st this will have reduced to just over 30 earlier. It will be about 4.5° up and to the east just before sunrise. On the morning of the 6th there is a close conjunction of Venus and Mars. The problem is that Venus will be only some 3° up at the start of civil twilight. If you have a good horizon to the east, Venus, Magnitude -3.9, should then be visible a little north of east. Mars will be only 12 arc minutes away, one-fifth of a degree almost directly above Venus. At magnitude 1.8 it is doubtful if it will be visible by eye, but binoculars should show it up.

MARS, now a morning object, rises 45 minutes before the Sun on October 1 and just over 70 minutes before the Sun on the 31st as its angle from the Sun increases. This will make it a little more visible, but it will be only some 6° up at 5.30 am in Wellington. By then Mars will be 15° from Venus. Mars starts October in Leo and moves into Virgo on October 12.

JUPITER starts October in the evening sky. On the 1st, half an hour after sunset, it will be some 11° up almost due west. Spica will be 5° away to the lower left of the planet. Better views May be obtained a little while later, but Jupiter will set about 100 minutes after the Sun.

The planet will get steadily lower in the early evening sky during October to eventually get lost in twilight. Jupiter reaches conjunction with the Sun on the 27th, it will then be 963 million km, 6.43 AU, from the Earth and 5.44 AU beyond the Sun.

SATURN is readily visible in the evening sky during October although by the end of the month it will set a few minutes before midnight. The planet is in Ophiuchus moving away from Antares. The crescent moon passes Saturn on the evening of October 24. At 10 pm the two will be just over 4° apart with the moon below and to the right of Saturn. The magnitude 2.5 star eta Oph will be a similar distance away directly below the moon.

Outer Planets

URANUS is at opposition on the night of October 19/20 NZ time. The actual opposition is close to the time of the new moon. Uranus will be at its brightest, magnitude 5.7, and so May be visible to the naked eye from a dark sky site. Good eyesight will be needed.

NEPTUNE is also in the evening sky at magnitude 7.8 in Aquarius. On the night of October 3/4 the moon will occult Neptune for viewers in New Zealand. Times range from 12:16 at Invercargill to 12:42 at Auckland The moon will be near full, 94% lit, but the event should be visible with a modest telescope given Neptune's 7.8 magnitude.

The occultation will occur just a little north of centre on the moon unlit limb. The event will not be instantaneous, the disk of Neptune taking some 6.2 seconds to disappear completely.

Minor Planets

(1) CERES is a morning object in Cancer. It starts October at magnitude 8.8 and brightens slightly during the month to magnitude 8.6. (2) PALLAS is in Eridanus most of October but moves into Fornax on the 28th. During the month it brightens a little from magnitude 8.5 to 8.2. (7) IRIS is in Aries throughout October, brightening from magnitude 7.7 to 6.9 during the month, making it the brightest asteroid all month.

-- Brian Loader

7. Starpath Game Wins Future Transport Competition

In August a team of Riccarton High School students won the Y7-10 Best Game category in the nationwide Future Transport competition run by the New Zealand Transport Authority.

The Year 9 team developed a board game to inform users about an initiative using ?starpath pro? which is a sprayable coating that gives pathways an artificial glow at night which makes it safer for walkers and reduces need for lighting.

The team worked during term 2 on this as part of a collaborative project co-facilitated by their math and science teachers. As part of this the team had to provide evidence that they investigated transport challenges, developed solutions and connected with the community as well as produce the playable game itself.

The judges were impressed with their excellent documentation, in depth play testing and top notch design process. The students won $4000 in vouchers for the school and themselves as well as an article featuring their winning entry in an upcoming Interface magazine.

A video showcasing Starpath can be viewed at http://education.nzta.govt.nz/competition/winners-games

-- From a note forwarded by Karen Pollard from the Riccarton High School newsletter.

Steve Butler of the RASNZ Dark Skies Group adds: It is great to see the next generation adopting the idea of using less light at night. The game is also an interesting way to spread the word.

As it happens... at the launch of the Great Barrier Island International Dark Sky Sanctuary they had an Expo with displays related to astronomy or dark skies. One of the displays was by a New Zealand supplier of Starpath! He had samples of the path sealing product as well as Eco Discs which are glow in the dark disks which can be fixed down to define the edge of pathways. Cheaper that the full seal coating. I will bring two sample disks and a brochure to Mt Cook for the Festival.

Their website is: www.nevanadesigns.com The local agent is Wayne Renner, This email address is being protected from spambots. You need JavaScript enabled to view it., 021 688 946. He is based in Tauranga.

8. Variable Star News

Since about 2010 the American Association of Variable Star Observers (AAVSO) has been running an All Sky Automated Photometric Survey (APASS). A description of this survey has been posted recently on the AAVSO home page under the heading Recent Activity.

Through grants from the Robert Martin Ayers Sciences Fund and the AAVSO Endowment Fund, the AAVSO is performing an all-sky photometric survey. This survey is conducted in five filters: Johnson B and V, plus Sloan g?, r?, i?. It is valid from about 7th magnitude to about 17th magnitude. Precise, reliable standardized photometry in this magnitude range is in high demand, both from our observers and from the professional community. Such a catalogue allows many research programs to quickly establish transformation between systems and efficiently achieve conversion of photometry to more fundamental physical properties. It will bridge the gap between Tycho2 and Sloane Digital Sky Survey, plus cover the entire sky at the same depth as the UCAC catalogue published by US Naval Observatory. The survey will take approximately one more year to complete. Data release 1 of APASS occurred on 2010 September 10. Since then the southern sky has been surveyed and this exercise May have benefitted from knowledge developed in the initial surveys.

The current Data Release version is DR 9 (29 July 2015). The article posted includes a history of the development work, documents limitations in the data acquisition processes and gives hints on using the data. Address https://www.aavso.org/ Home page ? Recent Activity.

-- Alan Baldwin

9. New Supernova Analysis Reframes Dark Energy Debate

The accelerating expansion of the Universe May not be real, but could just be an apparent effect, according to new research published in the journal Monthly Notices of the Royal Astronomical Society. The new study?by a group at the University of Canterbury in Christchurch, New Zealand?finds the fit of Type Ia supernovae to a model universe with no dark energy to be very slightly better than the fit to the standard dark energy model.

Dark energy is usually assumed to form roughly 70% of the present material content of the Universe. However, this mysterious quantity is essentially a place-holder for unknown physics.

Current models of the Universe require this dark energy term to explain the observed acceleration in the rate at which the Universe is expanding. Scientists base this conclusion on measurements of the distances to supernova explosions in distant galaxies, which appear to be farther away than they should be if the Universe?s expansion were not accelerating.

However, just how statistically significant this signature of cosmic acceleration is has been hotly debated in the past year. The previous debate pitted the standard Lambda Cold Dark Matter (?CDM) cosmology against an empty universe whose expansion neither accelerates nor decelerates. Both of these models though assume a simplified 100 year old cosmic expansion law ? Friedmann's equation.

Friedmann's equation assumes an expansion identical to that of a featureless soup, with no complicating structure. However, the present Universe actually contains a complex cosmic web of galaxy clusters in sheets and filaments that surround and thread vast empty voids.

Prof David Wiltshire, who led the study from the University of Canterbury in Christchurch, said, ?The past debate missed an essential point; if dark energy does not exist then a likely alternative is that the average expansion law does not follow Friedmann's equation.?

Rather than comparing the standard ?CDM cosmological model with an empty universe, the new study compares the fit of supernova data in ?CDM to a different model, called the ?timescape cosmology?. This has no dark energy. Instead, clocks carried by observers in galaxies differ from the clock that best describes average expansion once the lumpiness of structure in the Universe becomes significant. Whether or not one infers accelerating expansion then depends crucially on the clock used.

The timescape cosmology was found to give a slightly better fit to the largest supernova data catalogue than the ?CDM cosmology. Unfortunately the statistical evidence is not yet strong enough to rule definitively in favour of one model or the other, but future missions such as the European Space Agency?s Euclid satellite will have the power to distinguish between the standard cosmology and other models, and help scientists to decide whether dark energy is real or not.

Deciding that not only requires more data, but also better understanding properties of supernovae which currently limit the precision with which they can be used to measure distances. On that score, the new study shows significant unexpected effects which are missed if only one expansion law is applied. Consequently, even as a toy model the timescape cosmology provides a powerful tool to test our current understanding, and casts new light on our most profound cosmic questions.

-- Press release from the Royal Astronomical Society (U.K.). See it with images at https://www.ras.org.uk/news-and-press/3046-new-supernova-analysis-reframes-dark-energy-debate

10. ASKAP Joins the Hunt for Fast Radio Bursts

A new telescope, the Australian Square Kilometre Array Pathfinder (ASKAP), has joined the search for energetic and elusive fast radio bursts (FRBs). And in just a few days of looking, it?s already had success!

FRBs are mysterious millisecond-duration radio pulses that were first discovered around a decade ago. Since that time ? particularly in recent years ? we?ve made some progress toward the goal of localizing them. We?re now fairly convinced that FRBs come from outside of the galaxy, and yet they?re enormously bright ? orders of magnitude more luminous than any pulse seen from the Milky Way.

Better identification of where these mysterious bursts come from would help us to determine what they are. But so far, we?ve discovered only around 30 such bursts, despite the fact that they?re estimated to occur at a rate of ~3,000 events per day across the whole sky.

They are hard to find due to their short duration. Effective detection would require instantaneous coverage of a very large fraction of the sky. The Parkes radio telescope ? which has detected all but five of the fast radio bursts published to date ? has a field of view of 0.6 square degrees, significantly limiting our ability to rapidly survey for these transients.

ASKAP is a wide-field radio telescope made up of an array of 12-meter antennas. Using phased-array-feed technology, it is able to instantaneously observe an effective area of 160 square degrees ? an enormous field compared to Parkes?s! This capability significantly increases our chances of being able to detect fast radio bursts.

In a new study led by Keith Bannister (Australia Telescope National Facility, CSIRO Astronomy and Space Science), a team of scientists presented results from ASKAP?s first 3.4-day pilot survey. Bannister and collaborators announced that, in this brief time, ASKAP detected a fast radio burst: FRB 170107, an especially luminous, ~2 millisecond burst. It confirms the presence of an ultra-bright population of FRBs.

The discovery and characterization of a burst already after such a short initial campaign suggests that ASKAP will become a very powerful tool for detecting FRBs ? including some of the rarest bursts, ultra-bright ones like FRB 170107. Using the multiple bands of ASKAP, the authors were able to constrain the position of FRB 170107 to a region just 8? x 8? in size. No known field galaxies exist in that region, so we?re still not sure exactly where it came from, but this localization is already a significant achievement.

-- Abridged from the American Astronomical Society's 'Nova' of 24 May 2017. Citation: K. W. Bannister et al 2017 ApJL 841 L12. doi:10.3847/2041-8213/aa71ff See http://www.skyandtelescope.com/astronomy-news/askap-joins-the-hunt-for-mysterious-bursts/ for images and other citations.

11. Future Star Encounters

The movements of more than 300 000 stars surveyed by the European Space Agency's (ESA's) Gaia satellite reveal that rare close encounters with our Sun might disturb the cloud of comets at the far reaches of our Solar System, sending some towards Earth in the distant future.

As the Solar System moves through the Galaxy, and as other stars move on their own paths, close encounters are inevitable ? though 'close' still means many trillions of kilometres.

A star, depending on its mass and speed, would need to get within about 60 trillion kilometres or 400 000 AU before it starts to have an effect on the Solar System's distant reservoir of comets, the Oort Cloud, which is thought to extend out to 100 000 AU. For comparison, the outermost planet Neptune orbits at an average distance of about 4.5 billion kilometres, or 30 AU. (One Astronomical Unit (AU) is the Sun?Earth distance. One light-year is 63 240 AU. Alpha Centauri, the closes naked-eye star, is 270 000 AU away.)

The gravitational influence of stars that pass near the Oort Cloud could perturb the paths of comets residing there, jolting them onto orbits that bring them in to the inner Solar System. While this is thought to be responsible for some of the comets that appear in our skies, it also has the potential to put comets on a collision course with Earth or other planets.

Understanding the past and future motions of stars is a key goal of Gaia as it collects precise data on stellar positions and motions over its five-year mission. After 14 months, the first catalogue of more than a billion stars was recently released, which included the distances and the motions across the sky for more than two million stars.

By combining the new results with existing information, astronomers began a detailed, large-scale search for stars passing close to our Sun. So far, the motions relative to the Sun of more than 300 000 stars have been traced through the Galaxy and their closest approach determined for up to five million years in the past and future. Of them, 97 stars were found that will pass within one million AU, while 16 come within about 400 000 AU.

A particularly close encounter of one star, Gliese 710, in 1.3 million years' time, stands out. Thanks to the Gaia data it is predicted to pass around 16 000 AU from the Sun, well within the Oort Cloud. Furthermore, although Gliese 710 has a mass of 60% that of our Sun, it travels much slower than most stars: nearly 14 km/s (50 000 kph) compared with the average 28 km/s. The speed of its passage means it will have plenty of time to exert its gravitational influence on bodies in the Oort Cloud, potentially sending showers of comets into the Solar System. During its close approach Gliese 710 will be the brightest star in the night sky.

Importantly, the latest study used Gaia measurements to make a general estimate of the rate of stellar encounters, taking into account uncertainties such as stars that might not have been included in the previous catalogues. For 5 million years in the past and into the future, the overall encounter rate is estimated to be around 550 stars per million years coming within one million AU or 16 light-years, of which about 20 would come closer than 3.2 light-years. That equates to about one potential 'close' encounter every 50 000 years or so.

These estimates will be refined with future Gaia data releases. The second is scheduled for next April, containing the information for about 20 times as many stars, and many more distant stars as well, allowing reconstructions up to 25 million years into the past and future.

Reference: "The completeness-corrected rate of stellar encounters with the Sun from the first Gaia data release," by C.A.L. Bailer-Jones, published in Astronomy & Astrophysics.

-- From an ESA press release at: http://sci.esa.int/gaia/59435-close-encounters-of-the-stellar-kind/

12. How to Join the RASNZ

RASNZ membership is open to all individuals with an interest in astronomy in New Zealand. Information about the society and its objects can be found at http://rasnz.org.nz/rasnz/membership-benefits A membership form can be either obtained from This email address is being protected from spambots. You need JavaScript enabled to view it. or by completing the online application form found at http://rasnz.org.nz/rasnz/membership-application Basic membership for the 2017 year starts at $40 for an ordinary member, which includes an electronic subscription to our journal 'Southern Stars'.

13. Quotes

"In order to arrive at what you do not know
You must go by a way which is the way of ignorance."
-- T.S. Eliot, 'Four Quartets, East Coker'.
"Not every mistake is a foolish one." -- Cicero.

Newsletter editor:

Alan Gilmore Phone: 03 680 6817
P.O. Box 57 Email: This email address is being protected from spambots. You need JavaScript enabled to view it.
Lake Tekapo 7945
New Zealand