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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. Real Star Wars
2. Notice of AGM
3. Affiliated Societies Committee Meeting
4. The Solar System in April
5. GLOBE at Night 2013 Campaign
6. RASNZ Conference 2013
7. Seventh Trans-Tasman Symposium on Occultations
8. Canon DH40 Body for Sale
9. Improved LMC Distance Measure
10. Sizing Up Neutron Stars
11. Comet to Hit Mars in October 2014?
12. How to Join the RASNZ
13. Quote

1. Real Star Wars

Geography matters. In 1908 a rock the size of a city block hit the Earth´s atmosphere at 15km (9 miles) a second. The explosion flattened an area the size of London. But the land in question was in Siberia, so few people noticed and those who did had little influence. Suppose, though, it had devastated a city in Europe or North America. The history of the 20th century would have been different, as the best scientific and engineering brains were brought to bear on the question of how to stop it happening again.

Well, it has happened again, albeit less spectacularly. By chance, Siberia bore the brunt once more, when a meteor crashed in the Urals on February 15th, injuring more than 1,000 people. It could just as easily have hit Germany or Guangdong. Moreover, on the same day another, larger rock called 2012 DA14 passed within 27,000 km of Earth. By astronomical standards, that is a hair´s breadth. It is time to think seriously about stopping such incidents by building a system that can detect space rocks with sufficient warning, and then either blast them or push them out of the way. It would be costly, of course, and would require the development of new technology. But, as luck would have it, there is a tool lying around that has both the money and the nous to do it, and which is currently underemployed and in need of a new mission.

NASA, America´s space agency, has become a curious hybrid. Part of it is one of the world´s leading scientific research organisations. This NASA sends robot probes to the planets, runs space telescopes and has already sponsored projects devoted to looking for large asteroids-the ones that would blow humanity to kingdom come if their orbits ever intersected that of the Earth. If such a large, "planet-killing" asteroid were discovered, though, the chances are that earthlings would have decades, or centuries, to act; a small nudge, judiciously applied by rocket motor or nuclear explosion (see link below), would be enough to send it off course.

The real problem is "city-killers" - things too small for existing surveys to see, but large enough to do serious damage. And it is here that the other NASA might be brought into play. The non-scientific bit of the agency, the bit that brought you the Apollo project, has been looking for a proper job since 1972, when Apollo was cancelled. It thought it had found it in the Space Shuttle, but building a cheap, reliable orbital truck proved impossible. It thought it had found it in the International Space Station, but that has turned into a scientifically useless tin can in the sky. The latest wheeze is to build a rocket that might one day, many administrations hence, go to Mars.

In a well-ordered world, this bit of NASA would have been closed down years ago. That it has not been is due, in large measure, to the lobbying power of aerospace companies which see the agency as a way to divert money from taxpayers´ pockets into those of their shareholders. This pocket- picking would be less irksome if something useful came of it. Why not, therefore, change this part of NASA´s remit to protecting the planet from external attack, not by evil aliens but by an uncaring universe?

Two things would be needed. One is a bigger system of telescopes, either on the ground or in orbit, to give notice of a threat. The other is a way to counter the threat. That might be done with lasers, or with controlled explosions that would shift the incoming object´s orbit sufficiently to make it miss altogether, or (if that is not possible) hit an unpopulated area.

Developing all this would be a technological challenge worthy of NASA´s engineers. It would keep the agency´s bureaucrats in their jobs. It would keep the money flowing to the aerospace companies. It would probably cost no more than the space station (about $100 billion). And, if it worked, it would provide something that benefited not just America, but the world - precisely the sort of thing a rich country which often claims the moral high ground ought to be doing. When Apollo 11 took off from the Moon on July 21st 1969, its crew left behind a plaque that read, "They came in peace, for all mankind". What an opportunity both America and NASA now have to prove that they meant it.

-- From The Economist, February 23 p.16. See the original at http://www.economist.com/news/leaders/21572203-something-useful-americas-underemployed-space-agency-do-real-star-war For a longer article on this topic see http://www.economist.com/news/science-and-technology/21572162-after-hit-and-near-miss-minds-are-focusing-risks-space-rocks

2. Notice of AGM

The 90th Annual General Meeting of the Royal Astronomical Society of New Zealand will be held at about 4:30 pm on Saturday the 25th of May in the Oreti-Aparima Room of the Ascot Park Hotel, Invercargill. Notices of Motion are invited and should reach the Executive Secretary six weeks in advance of the meeting, by April 20, 2013. They should be sent in writing to: R O'Keeffe, Executive Secretary, RASNZ, 662 Onewhero-Tuakau Bridge Rd, RD 2, TUAKAU 2697. Email: This email address is being protected from spambots. You need JavaScript enabled to view it.

3. Affiliated Societies Committee Meeting

The Affiliated Societies Committee will meet on Friday the 24th of May 2013 at the Ascot Park Hotel, Invercargill. This meeting is normally attended by the Presidents of Affiliated Societies or their nominated representative. Notices of Motion for the meeting are invited and should reach the Executive Secretary by April 19, 2013.

-- R O´Keeffe, Executive Secretary, RASNZ.

4. The Solar System in April

PHASES OF THE MOON (times as shown by GUIDE)

Last quarter:  Apr  3 at  5.37 pm NZDT (04:37 UT)        
New moon:      Apr 10 at  9.35 pm NZST (09:35 UT)        
First quarter: Apr 19 at 12.31 am NZST (Apr 18, 12:31 UT)
Full moon:     Apr 26 at  7.57 am NZST (Apr 25, 19:57 UT)

The planets in april

Jupiter sets just over 2.5 hours after the Sun at the beginning of April and about 1.5 hours after it at the end of the month, so will be low to the northwest following sunset.

Saturn is at opposition at the end of April. It will be an easily seen object mid to late evening throughout the month.

Mercury is in the morning sky. The first half of April will present the best morning views of the planet for the year.

Venus and Mars are both too close to the Sun to observe during April.

The evening sky.

Venus was at superior conjunction at the end of March. In April it is an evening object, but will set less than half an hour after the Sun so will be at best very difficult to see.

Mars is at conjunction with the Sun on April 18, so will also not be visible during April. After conjunction it will become a morning sky object.

Jupiter sets just over 2.5 hours after the Sun at the beginning of April and about 1.5 hours after it at the end of the month. 30 minutes after sunset it will be visible to the northwest, about 21° up on the 1st, reducing to 15° by the 30th. The planet remains in Taurus with Aldebaran to its left, their separation increasing from a little over 5° on the 1st to 9° during April.

The crescent moon passes Jupiter on the morning of the 15th. They are closest about 6 am while Jupiter is set in NZ. The previous evening the two will be about 6.5° apart with the moon left of Jupiter. The following evening they will be about a degree closer, but with the moon now to the right of Jupiter.

Saturn is at opposition on April 28 and becomes a good evening object during the month. On the 1st it will rise a little after 8.30 pm, NZDT. By the end of April it will rise a few minutes after 5.30 pm NZST. Two hours after it rises, the planet will be a little over 20° up to the east

Saturn is in Libra all April with the wide double star alpha Lib a few degrees to its right. Alpha Lib has a magnitude 2.7, its companion 5.2. Beta Lib will be about twice as far away to the lower right of the planet. Despite its name, beta is slightly brighter than alpha. The star Spica, will be another step further away to the upper left of Saturn. At magnitude 1.1 Spica is the brightest of the three star, but Saturn is a magnitude brighter still.

The moon, a few hours past full, will be some 5° to the right of Saturn in the early evening of April 26. During the evening the moon will slowly move further from Saturn towards the star alpha Lib. The moon will occult the star soon after 10.30 pm as seen in New Zealand, times varying by a few minutes through the country. This disappearance takes place on the lit limb of the moon making it very difficult to observe. Just over an hour later the star emerges again from the opposite side of the moon.

The morning sky: mercury (and saturn)

Mercury, in the morning sky, rises more than 2 hours before the Sun during the first half of April. An hour before sunrise it will be an easy object to the east about 15° above the horizon.

It starts the month at magnitude 0.3 and brightens to -0.1 by the 15th and -0.9 by the 30th. This makes it the brightest star-like object in the eastern sky.

During the second half of April the planet will become lower in the morning sky, by the 30th it rises only 70 minutes before the Sun The lower altitude will be compensate by its increasing brightness so it should be visible 45 minutes before sunrise.

On the morning of the 21st Mercury will be 2° to the right of Uranus. At magnitude 5.9 Uranus is readily visible through binoculars as the brightest object to the right of Mercury. A star, half a magnitude fainter than Uranus will be quite close to its lower. This should present a good opportunity to view the outer planet.

Saturn in the morning sky becomes very low to the west before sunrise so will only be readily visible well before that time.

Outer planets

Uranus moves up into the morning sky. Its conjunction with Mercury on the 21st is note above.

Neptune is a 7.9 magnitude, morning object in Aquarius, some 30° above and to the left of Mercury. The 14% lit crescent moon will be 6° to the left of Neptune on the morning of April 7.

Brighter asteroids:

Both (1) Ceres and (4) Vesta move away from Jupiter and Aldebaran during April.

Ceres spends the month in Auriga with a magnitude near 8.7. Vesta is in Taurus most of the month but moves into Gemini on the 26th. Its magnitude is near 8.3

-- Brian Loader

5. GLOBE at Night 2013 Campaign

Join the Worldwide GLOBE at Night 2013 Campaign

What would it be like without stars at night? What is it we lose? Starry night skies have given us poetry, art, music and the wonder to explore. A bright night sky (aka light pollution) affects energy consumption, health and wildlife too. Spend a few minutes to help scientists by measuring the brightness of your night sky. Join the GLOBE at Night citizen-science campaign (www.globeatnight.org). The third campaign started March 3 and runs through March 12.

More information: GLOBE at Night is a worldwide, hands-on science and education program to encourage citizen-scientists worldwide to record the brightness of their night sky. During five select sets of dates in 2013, children and adults match the appearance of a constellation (Orion or Leo in the northern hemisphere, and Orion and Crux in the southern hemisphere) with seven star charts of progressively fainter stars (www.globeatnight.org/observe_magnitude_orion.html). Participants then submit their choice of star chart at www.globeatnight.org/webapp/ with their date, time and location. This can be done by computer (after the measurement) or by smart phone or pad (during the measurement). From these data an interactive map of all worldwide observations is created (www.globeatnight.org/map/). Over the past 7 years of 10-day campaigns, people in 115 countries have contributed over 83,000 measurements, making GLOBE at Night the most popular, light pollution citizen-science campaign to date (www.globeatnight.org/analyze.html).

The GLOBE at Night website is easy to use, comprehensive, and holds an abundance of background information (www.globeatnight.org/learn.html and www.globeatnight.org/observe.html). Guides, activities, one-page flyers and postcards advertising the campaign are available at www.globeatnight.org/pdf/. Through GLOBE at Night, students, teachers, parents and community members are amassing a data set from which they can explore the nature of light pollution locally and across the globe. The remaining GLOBE at Night campaigns in 2013 are: March 3 - 12, March 31 - April 9, and April 29 - May 8. Make a difference and join the GLOBE at Night campaign.

-- Constance E. Walker, Ph.D. associate scientist & senior science education specialist, NOAO director, GLOBE at Night campaign (www.globeatnight.org) This email address is being protected from spambots. You need JavaScript enabled to view it.

-- Forwarded by Steve Butler

6. RASNZ Conference 2013

The 2013 conference is now a little over 2 months away. Registrations for the conference are coming in regularly. If you have yet to do so, it would be wise to register now and book your accommodation. The venue is the Ascot Park Hotel, Invercargill, the dates Friday 24 to Sunday 26 May, with the Trans Tasman Occultation Symposium, TTSO7 following on Monday 27 and Tuesday 28 May.

Visit the RASNZ web site at <http://www.rasnz.org.nz> for more details and to register for the conference and/or TTSO7. We encourage members to present papers on their own observing activities or other items of astronomical interest. Submission forms to present a paper are also on the web site.

If you are booking accommodation at the Ascot Park Hotel make sure you mention that you are attending the RASNZ conference. The hotel is holding accommodation for us for a limited time and special rates will apply. With the Bluff Oyster festival coinciding with the conference it is sensible to reserve your accommodation early before it is booked out.

If you intend flying to Invercargill you may be interested in using the shuttle from the airport. Let the LOC know you are flying and they will send you a voucher to entitle you to a shuttle fare of $5 each way.

The LOC are planning a tour for the Friday afternoon before the conference opens. Their plans includes a visit to the Unwin Radar at Awarua, then to the Met Station to watch a balloon release and radar tracking, then onto Richardson' Truck Museum. Cost is $20 per person which includes bus hire and admission to the Truck Museum. The tour will depart from the Ascot Hotel at 1pm returning about 4pm. More information will be available from the LOC

In response to requests, the LOC are arranging a theme for the banquet. Realising that November 23rd this year is the 50th anniversary of the first transmission of Dr Who on BBC TV, they have decided on the theme "50 Years of Dr Who". For more information on the above, the LOC can be contacted at <This email address is being protected from spambots. You need JavaScript enabled to view it.>.

An updated version of the conference brochure is now on the RASNZ web site. It includes details of our two guest speakers, Jean-François Kaufeler and Professor Richard Easther. Jean-François was until recently at the ESA where he was head of the ground segment engineering department and of the ESA operations centre. Richard Easther is the Head of Department, Physics, at Auckland University. The fellows speaker for 2013 is Bob Evans and our after dinner speaker will be the Hon. Margaret Austin.

Further details of the plans for the TTSO7 meeting are available on the Occultation Section web page <http://www.occultations.org.nz>.

-- Brian Loader, Chair, RASNZ SCC. 12 March 2013

7. Seventh Trans-Tasman Symposium on Occultations

This is a reminder that the Seventh Trans-Tasman Symposium on Occultations (TTSO7) will take place in Invercargill over Monday May 27 and Tuesday May 28, 2013, immediately following the RASNZ Conference.

TTSO meetings are held in New Zealand and Australia over alternate years and attract a wide variety of participants. Their purpose is to provide a forum to swap information, experiences and ideas, and to discuss new techniques in observing occultations. The meetings are designed to cater for both new and seasoned observers so prior experience with this form of observing is not a prerequisite for attending.

A focus of this year´s meeting will be the launch of the new Astronomical Digital Video System (ADVS) developed by Tony Barry, Dave Gault and Hristo Pavlov. This revolutionary new system has been designed from the ground up to overcome ALL of the problems associated with using current video systems to observe occultations. Tony and Dave will bring with them a full working model so that TTSO7 participants will be able to get some "hands on" experience. More information about the ADVS is available at: http://www.astrodigitalvideo.com.au/

There is still time in the programme for additional presentations, in either oral form or as poster papers. Presentations can be on any occultation-related topic. If you would like to give a presentation please send a title, brief abstract and requested duration in the case of oral presentations, to the TTSO7 convenor, Murray Forbes (This email address is being protected from spambots. You need JavaScript enabled to view it.) with a copy to Graham Blow (This email address is being protected from spambots. You need JavaScript enabled to view it.). At the meeting digital copies of all presentations will be required in a form suitable for inclusion on the Symposium CD.

For more information please visit the TTSO7 website: http://www.occultations.org.nz/meetings/TTSO7/index.htm

-- Graham Blow & Murray Forbes

8. Canon DH40 Body for Sale

For Sale: Canon DH40 Body Only, Spectrum enhanced DSLR with built-in astronomical UV/IR blocking Filter (Type 1b) Serial No. 0820519094: Frame Count 2124 Plus: Two (2) spare batteries and cables, Instruction booklet. Price: $1100.00 o.n.o. Contact: Peter Aldous - 03 6937337 or email This email address is being protected from spambots. You need JavaScript enabled to view it.


Peter has also discovered a supernova, the first in his search programme. However the discovery hasn't been officially designated or announced at the press time. -Ed.

9. Improved LMC Distance Measure

After nearly a decade of careful observations an international team of astronomers has measured the distance to our neighbouring galaxy, the Large Magellanic Cloud, more accurately than ever before. This new measurement also improves our knowledge of the rate of expansion of the universe, the Hubble Constant. It is also a crucial step towards understanding the nature of the mysterious dark energy that is causing the expansion to accelerate. The team used telescopes at the European Southern Observatory's (ESO) La Silla Observatory in Chile as well as others around the globe. These results appeared in the 7 March 2013 issue of the journal Nature.

Astronomers survey the scale of the universe by first measuring the distances to close-by objects and then using them as standard candles to pin down distances further and further out into the cosmos. But this chain is only as accurate as its weakest link. Up to now finding an accurate distance to the Large Magellanic Cloud (LMC) has proved elusive. It is crucially important ss stars in the LMC are used to fix the distance scale for more remote galaxies.

Careful observations of a rare class of double star have now allowed a team of astronomers to deduce a much more precise value for the LMC distance: 163,000 light-years. The result is accurate to 2%.

The improvement in the measurement of the distance to the Large Magellanic Cloud also gives better distances for many Cepheid variable stars. These bright pulsating stars are used as standard candles to measure distances out to more remote galaxies. This in turn is the basis for surveying the universe out to the most distant galaxies that can be seen with current telescopes. So this more accurate distance for the Large Magellanic Cloud improves the accuracy of cosmological distances.

The astronomers worked out the distance to the Large Magellanic Cloud by observing rare close pairs of stars, known as eclipsing binaries. As these stars orbit each other they pass in front of each other, as seen from Earth. When this happens the total brightness drops.

By tracking these changes in brightness, and also measuring the stars' orbital speeds, it is possible to work out the sizes of the stars, their masses, and other information about their orbits. When this is combined with careful measurements of the total brightness and colours of the stars remarkably accurate distances can be found.

This method has been used before, but with hot stars. However, certain assumptions have to be made in this case so such distances are not as accurate. But now, for the first time, eight extremely rare eclipsing binaries where both stars are cool red giant stars have been identified. These stars have been studied very carefully and yield much more accurate distance values -- accurate to about 2%.

The result was achieved using ESO's HARPS spectrograph for extremely accurate radial velocities of relatively faint stars. The researchers also used the SOFI instrument for precise measurements of star brightness in the infrared

For text, images, and video: http://www.eso.org/public/news/eso1311/

-- From an ESO press release forwarded by Karen Pollard.

10. Sizing Up Neutron Stars

Neutron stars, the ultra-dense cores left behind after massive stars collapse, contain the densest matter known in the universe outside of a black hole. New results from X-ray telescopes have provided one of the most reliable determinations yet of the relation between the radius of a neutron star and its mass. These results constrain how nuclear matter -- protons and neutrons, and their constituent quarks -- interact under the extreme conditions found in neutron stars.

Three telescopes -- Chandra, ESA's XMM-Newton, and NASA's Rossi X-ray Timing Explorer (RXTE) -- were used to observe 8 neutron stars.

An x-ray star X7 in the globular cluster 47 Tucanae is a neutron star slowly pulling gas away from a small companion star. In 2006, researchers used observations of the amount of X-rays from X7 at different energies to determine a relationship between the mass and the radius of the neutron star. A similar procedure was used for observations of the other neutron stars.

Four other neutron stars were observed to undergo bursts of X-rays that cause the atmosphere of the neutron star to expand. By following the cooling of the star, its surface area can be calculated. From that it was possible to gather more information on the relationships between the masses and radii of these neutron stars.

The mass and radius of a neutron star is directly related to interactions between the particles in the interior of the star. So these results give new information about the interiors of neutron stars. The conclusion was that the radius of a neutron star with a mass that is 1.4 times the mass of the Sun is between 10.4 and 12.9 km. The density at the centre about 8 times that of nuclear matter found in Earth-like conditions.

The new values for the neutron star's structure should hold true even if matter composed of free quarks exists in the core of the star. Quarks are fundamental particles that combine to form protons and neutrons and are not usually found in isolation. It has been postulated that free quarks may exist inside the centres of neutron stars, but no firm evidence for this has ever been found.

The results also have implications for the study of atomic nuclei generally, such as the distances between neutrons and the so-called 'symmetry energy' for nuclear matter.

Text & Image: http://www.chandra.si.edu/photo/2013/47tuc/ http://www.nasa.gov/mission_pages/chandra/multimedia/x7.html

-- From a NASA Chandra X-ray Center and NASA Marshall Space Flight Center press release forwarded by Karen Pollard.

11. Comet to Hit Mars in October 2014?

Have you heard, it´s in the stars Next October, it collides with Mars. Maybe Earlier this year, the scientists operating a spacecraft called Mars Reconnaissance Orbiter started making plans to look at something other than Mars. Their calculations showed that a newly discovered comet called ISON will come within 10 million kilometres of their spacecraft in September. Comet ISON is causing quite a stir in astronomical circles, because if, after whizzing past Mars, it survives a close shave with the sun, there is a good chance that it will go on to emblazon itself spectacularly across the skies of Earth. How handy, astronomers thought, that there should be a spacecraft near enough to the comet´s inbound track to break off from its day job and take a first good look at this newcomer from the outer depths of the solar system.

Now Mars Reconnaissance Orbiter´s operators have a second comet to study, and this one looks like coming 200 times closer than comet ISON will. This particular comet has the awkward name C/2013 A1 (Siding Spring). It was discovered on January 3rd by Rob McNaught at Siding Spring observatory in Australia. (It isn't called Comet McNaught because Rob reported it as an asteroid and observations were published before its cometary nature was detected.) Calculations of its trajectory by researchers at NASA have it passing about 50,000km from Mars on October 19th 2014. That is close enough for HiRise, the remarkably acute telescope on Mars Reconnaissance Orbiter, to pick out features that are just a few tens of metres across on the solid nucleus which forms the comet´s heart.

Predicting the trajectories of recently discovered comets is a necessarily imprecise business, so C/2013 A1 (Siding Spring) could yet end up farther off, missing Mars by a bit over 300,000km. But it is also possible that it will not miss Mars at all.

Calculated today, the odds of the comet hitting the planet are about 700 to one, says Paul Chodas of JPL, the laboratory in California that runs Mars Reconnaissance Orbiter. If that were to happen, it would be not merely an incredible sight, it would also be a huge scientific opportunity.

The nucleus of C/2013 A1 may be as small as 4km across. It may be ten times that. The speed at which it will be travelling when it comes closest to Mars, though, is known precisely: just under 56km a second. An 8km comet weighing 200 billion tonnes hitting Mars at that velocity would produce a blast equivalent to 60 million megatons of high explosive - a million times the yield of the largest hydrogen bomb ever tested. If the impact takes place on the side of Mars visible from the Earth, observers will see the planet flare up like a flash gun.

Jay Melosh of Purdue University has done some calculations on the assumption that the nucleus is 8km across. The crater formed on the Martian surface by the impact of such a nucleus would be about 160km wide. Watching this hole being torn in the planet´s crust and charting the crater´s subsequent development over hours, months and years would be a remarkable opportunity for planetary geologists. Most of the solid surfaces in the solar system are pockmarked with large craters, and much has been deduced about the processes that take place when they form. Actually seeing one created would put those deductions to the test. If the geology would be fascinating, the astrobiology would be even better. Beneath the surface of Mars there is ice - something which HiRise has confirmed by detecting its telltale glint at the bottom of newly formed craters of far less dramatic size. A cometary impact would melt a great deal of that ice. Judging by the signs of erosion and sedimentation that can be seen in Mars´s Mojave crater, a 60km-wide hole formed about 5m years ago, there would be water at the surface too, scouring the newly created landscape. Some of it might eventually form lakes which, though they would quickly be covered by ice because Mars´s atmosphere is so cold, would remain liquid below the ice-kept warm by the heat the impact generated in the underlying rock. More water would flow through cracks in those rocks. And the rocks would stay hot a long time. A patch of Mars the size of Wales would be warm and wet for millions of years.

If there are, as some would like to believe, microbes on Mars, they seem to be hiding below the surface and doing little to make themselves known. An impact big enough to melt a lot of ice may be, for them, what the rare desert rains are for the plants of America´s original Mojave: a brief chance to come out and thrive. On Earth large impacts bring death. The C2013/A1 impact, should it occur, will be similar in scale to the blast that dispatched the dinosaurs, and millions of other species, 66 million years ago at the end of the Cretaceous period. On Mars, though, such impacts may bring life, by offering sporadic oases in the dry, cold desert of the planet´s history.

A fresh crater of such scale would be a compelling new focus for planetary science, especially if it held signs of life. For the scientific instruments currently on and around Mars, though, it might prove a mixed blessing.

NASA´s Mars rovers, Curiosity and Opportunity, do not seem to be directly in the line of fire. If the comet does hit, the bulls-eye is likely to be the planet´s southern highlands, and the rovers are near the equator. They should see the flash, though, and will perhaps record all sorts of strange atmospheric phenomena. Curiosity should be able to measure subsequent changes in the atmosphere´s pressure and composition, too. (Opportunity does not have the relevant instruments.) And there is a chance that some of the hundreds of billions of tonnes of rock thrown up into the sky could come back down close enough for either rover to trundle off and study them. The downside of that possibility is that a returning rock might actually hit one of the rovers.

Spacecraft in orbit around Mars - NASA´s Mars Reconnaissance Orbiter, Mars Odyssey and MAVEN (which will have just arrived), and the European Space Agency´s Mars Express - are at greater risk that way. Lots of high- velocity grapeshot will be thrown across their orbits. Dr Melosh thinks he could work out how dangerous this might be using calculations he and some colleagues made previously, when working out the amount of Martian material the creation of Mojave crater would have deposited on Mars´s moons.

Further observations will, all likelihood, rule out an impact, though they may not do so definitively for some time yet. Even if the comet does not hit Mars, though, it poses some risk to the spacecraft in orbit. When they get into the inner solar system - within the orbit of Jupiter, about three times farther from the sun than Mars - comets develop a thin atmosphere of gas and dust called a coma. It looks likely that C/2013 A1´s coma will engulf the spacecraft around Mars, putting them at some risk of encountering a bit of grit moving at dangerously high speed. Such risks are currently being studied, but they seem unlikely to be high.

Mars Reconnaissance Orbiter and its less capable colleagues will therefore get an unprecedented scientific opportunity. Spacecraft have got close to comets before, but only to periodic comets-those which have been forced into relatively short orbits round the sun, and thus have been warmed up and cooled down again repeatedly. C/2013 A1, like Comet ISON, is a pristine object making its first and probably only visit to the inner solar system. It represents the first chance to see primordial comet- stuff, unaltered since the beginning of the solar system, close up. That both comets will be passing near, perhaps very near, to spacecraft capable of doing something with the opportunity is a remarkable stroke of luck in itself. To hope for more seems almost greedy. But that is not going to stop a lot of scientists hoping for more most fervently.

-- From The Economist 9 March, p.76-77, with the discovery note amplified by Ed. See the original at http://www.economist.com/news/science-and-technology/21573086-next-october-it-collides-mars-maybe-have-you-heard-its-stars?zid=314&ah=607477d0cfcfc0adb6dd0ff57bb8e5c9


C/2013 A1 (Siding Spring) is currently an 18th magnitude object in NZ's northwest evening sky at dusk. It is 6.819 AU (1023 million km) from the Earth and 6.576 AU (986 million km) from the sun.

Its perihelion is on 2014 Oct. 25.47 UT when it will be 1.399 AU (210 million km) from the sun. The comet isn't expected to reach naked eye brightness, though one never really knows with comets. However it will be a nicely placed telescopic object in our sky through the winter of 2014. It will be circumpolar through much of August and September when it is at its closest to Earth, 0.89 AU or 134 million km away.

Though C/2013 A1 was discovered in January, pre-discovery positions have been identified back to 2012 October 4. So the current orbit is based on five months observations. - Ed.

12. How to Join the RASNZ

A membership application form and details can be found on the RASNZ website http://www.rasnz.org.nz/InfoForm/membform.htm. Please note that the weblink to membership forms is case sensitive. Alternatively please send an email to the membership secretary This email address is being protected from spambots. You need JavaScript enabled to view it. for further information.

The annual subscription rate is $75, not including the Yearbook. For overseas rates please check with the membership secretary, This email address is being protected from spambots. You need JavaScript enabled to view it..

13. Quote

"Outer space is no place for a person of breeding" -- Lady Violet Bonham-Carter.


Newsletter editor:

Alan Gilmore   Phone: 03 680 6000
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