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.


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

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'.


"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