RASNZ Electronic Newsletter May 2015
Email Newsletter Number 173
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. Graham Loftus
2. Brian Loader Elected a Fellow of the RASNZ
3. Tom Richards Made Honorary Member
4. RASNZ Supports the International Year of Light
5. The Solar System in June
6. Mt John's 50th Anniversary Symposium
7. RASNZ Conference
8. Young Star Clusters at High Galactic Latitudes
9. Mercury Mission Ends
1. Graham Loftus
Graham Loftus died on Saturday May 16. Graham was famous among the older New Zealand astronomers. He had a great passion for astronomy, great abilities as a telescope mirror maker, and was an all-round nice bloke. Tributes and memories followed the news of Graham's passing.
Bob Evans first knew Graham when he lived in Christchurch and was an active member of the Canterbury Astronomical Society. Bob recalled: "My vision of his driving his one cylinder Lantz tractor through 3 or 4 metre high old-man gorse at the newly acquired West Melton observatory site has never left me. His demonstration of cratering on the Moon using plaster of Paris meteoroids at a CAS meeting is another memory. Then when Stefan Mochnacki and I visited Auckland in early January 1969 to bring Clive Rowe's photometer, it was Graham that put us up. Like his telescopes, he was bigger than life."
Rod Austin recalled Graham as "One of the truly great characters of NZ astronomy. I had quite a bit to do with him when the Taranaki Active Astronomers Group was up and running, and he wrote several articles for the newsletter. Also of course in the days of Tikorangi Observatory and later the Cape Egmont Observatory. He made the mirrors for their big telescopes."
Stephen Hovell recalled that he and Graham "... used to see a lot of each other in the late 60s before I moved away from Auckland. I remember cherry brandies with Grant Christie at 1am while looking through his monster 20-inch."
The Editor's favourite memory of Graham's gentle humour is a note he wrote about testing one of his monster telescopes. Graham compared his view of a galaxy with its photo in an astronomy book but commented that "the galaxy seemed to have been photographed from the other side." Printing photos back to front was a common error, particularly with astronomical pictures.
2. Brian Loader Elected a Fellow of the RASNZ
At the May 9 AGM Brian Loader was elected a Fellow of the RASNZ on the nomination of Bob Evans, John Hearnshaw and Alan Gilmore. The citation follows. ---------
Brian Loader moved to New Zealand from the United Kingdom in the 1970s. He taught mathematics at Marlborough College and then worked at the USNO´s Astrometric Station on Black Birch as a programmer from the mid- 1980s until it closed in the 1990s. Brian moved to Christchurch in the late 1980s after Pauline got an IT job there.
Brian joined RASNZ in 1980 and was elected onto the council in 1986, remaining in that position until 1992. He was then elected Treasurer, retaining this position until 2004. He became RASNZ President for 2004-06, Vice-President 2006-08 and then Secretary 2008-10. Brian served as Chairperson on the RASNZ Standing Conference Committee until 2014.
Brian was awarded the 2014 Homer F. DaBoll award by the International Occultation Timing Association (IOTA). The award is presented to an individual who has made a significant contribution to occultation science, or to the work of IOTA. The DaBoll award to Brian reads: "For Total and Grazing lunar occultations, the Jovian Satellite eclipse program, lunar double star co-ordination, publications, and nurturing new occultation observers worldwide."
Brian joined the RASNZ Occultation Section in 1980 and immediately adopted a prominent role as a prolific observer of total and grazing occultations. From 1980 to the present he has timed over 6000 lunar occultations (averaging 183 per year) making him one of the top observers worldwide. Between 1980 and the end of 2013 he also observed 83 positive minor planet occultations. (His tenacity is illustrated by the fact that it took him until 1989 to see his first positive event.)
Also in 1980 Brian instituted the Jovian Satellite Eclipse programme which he co-ordinated for more than 20 years. This programme provided data to Dr Jay Lieske at JPL for use in updating the ephemerides of the Galilean satellites, a result of direct benefit to the Galileo mission. Starting about 1985, Brian also instituted and co-ordinated observations of the mutual events of the Galilean satellites across multiple seasons. In more recent times he has initiated and continues to co-ordinate the double star programme for the determination of true separations and position angles from occultation observations made at different locations. Observers from around the globe contribute to this programme, which has resulted in a string of publications, including a number in the Journal of Double Star Observations.
Brian has acted as a regional co-ordinator and reducer for total occultations for many years, a role which has required him to interact with and provide advice to almost every new observer in this part of the world. Together with his wife Pauline, Brian has for many years prepared and published annual summaries of upcoming bright total and grazing occultations for all of Australasia. These have materially assisted in attracting new observers to these events.
Brian's role in nurturing observers worldwide is also significant, especially in the field of double star occultations. He has acted as a mentor for many new observers, and has frequently presented on occultation matters at RASNZ, NACAA and TTSO meetings over more than three decades. Brian has also been Assistant Director of the RASNZ Occultation Section for almost 30 years.
3. Tom Richards Made Honorary Member
At the RASNZ's AGM on Saturday, May 9, members approved a motion that Tom Richards be made an Honorary Member of the RASNZ. The citation by Stan Walker and Alan Baldwin follows. -----
We wish to propose Thomas Richards, MA Hons, VUW, DPhil, Oxon, recently retired Director of Variable Stars South, as an Honorary Member of this Society. His successful resurrection of the almost defunct Variable Star Section of The Royal Astronomical Society of New Zealand in 2009, and the transformation of this into a thriving organisation with about 100 members, many engaged in serious observational and theoretical research, is an outstanding effort, deserving of high recognition. He has also arranged three symposia in conjunction with RASNZ Annual Conferences, initially at Tekapo in 2007, then VSSS2 at Wellington, 2009 and VSSS3 at Whakatane, 2014, which last event saw 33 participants from both Australia and New Zealand
In building up Variable Stars South he changed its approach by encouraging members to engage in projects with specific goals rather than just make observations to be stored in a database - often not to be used for decades. At this time there are five or six active groups, with other members making measures which are lodged directly with the AAVSO. Another success has been the development of a quarterly Newsletter, now edited by Phil Evans, which averages hundreds, occasionally thousands, of separate downloads each issue. Tom encouraged David O'Driscoll to develop this very informative and much consulted website which also contains many of the presentations at the Symposia, or at other venues such as the RASNZ Annual Conferences. Apart from this, members have published papers in refereed journals and collaborated with professional astronomers on specific projects, such as delta Scuti stars in eclipsing binaries or a major ongoing project involving QZ Carinae, a massive multiple star system.
Tom began his astronomical interest with solar observing at Wellington College Observatory and received the Murray Geddes prize in 1957. Around 1970, whilst lecturing at the University of Auckland, he set up a planetary group using the Edith Winstone Blackwell Telescope at Auckland Observatory. He also organised several highly successful grazing occultation expeditions and edited the AAS Newsletter. After accepting a position at La Trobe University in Melbourne he initially taught philosophy and, while there with his wife Lynn, he developed the Nvivo software that was the basis for the very successful QSR company QSR International. He became an Associate Professor in Computer Science.
Tom has retained his membership of our society through the years and in the last decade or so has presented papers at the Annual Conferences. He has been President of the Astronomical Society of Victoria and was a recipient of the Astronomical Society of Australia's Berenice Page Medal in 2006 for extensive and ongoing CCD photometry observations of light curves of variable stars and minor planets. Tom is now observing eclipsing binaries, mainly EWs and EBs but some EAs, analysing the data and updating the light elements of many of these. He has authored or been co-author of several refereed papers in this area.
4. RASNZ Supports the International Year of Light
The following press release has been circulated by the RASNZ. -----
The Royal Astronomical Society of New Zealand (RASNZ) is pleased to announce its support for the International Year of Light and Light Based Technologies.
The New Zealand Committee for the IYL2015 programme have approved the RASNZ as a Designated Activity. Astronomy is included as one of the programme streams for the IYL2015, with the programme "Cosmic Light" containing a range of activities that RASNZ will support and promote.
Light is at the core of astronomical study. Through major scientific discoveries and technological advancements, light has helped us to see and better understand the universe. The object of the RASNZ is the promotion and extension of knowledge of astronomy and related branches of science. It encourages interest in astronomy, and is an association of observers and others for mutual help and advancement of science. The society includes 23 Affiliated Societies based in communities around New Zealand and has several special interest sections and groups.
Wasteful artificial light at night obscures the night sky so careful application of new lighting technologies is needed to protect the night sky and the night environment.
The RASNZ will celebrate the International Year of Light through sharing events and experiences with the public, inviting senior students to attend the RASNZ annual conference, and extending knowledge of the universe at every opportunity.
The RASNZ will also continue work to raise concerns about unintended side effects of outdoor lighting.
-- Thanks to Steve Butler of the RASNZ Dark Skies group for passing this along.
5. The Solar System in June
Dates and times are NZST (UT + 12 hours) unless otherwise specified. Rise and set times are for Wellington. They will vary by a few minutes elsewhere in NZ.
The southern winter solstice is on the morning of June 22. The Sun will be furthest north at 4.38 am (June 21, 16:38 UT).
Sunrise, sunset and twilight times in june
June 1 NZST June 30 NZST morning evening morning evening rise: 7.33am, set: 5.03pm. rise: 7.45am, set: 5.03pm Twilights Civil: starts: 7.06am, ends: 5.31pm. starts: 7.16am, ends: 5.32pm Nautical: starts: 6.31am, ends: 6.06pm. starts: 6.42am, ends: 6.07pm Astro: starts: 5.58am, ends: 6.39pm. starts: 6.08am, ends: 6.41pm
June PHASES OF THE MOON (times as shown by GUIDE)
Full moon: June 3 at 4.19 am (Jun 2, 16:19 UT) Last quarter: June 10 at 3.42 am (Jun 9, 15:42 UT) New moon: June 17 at 2.05 am (Jun 16, 14:05 UT) First quarter: June 24 at 11.03 pm (11:03 UT)
The planets in june
Mercury becomes visible in the dawn sky by the end of June. Venus gets a little higher in the evening sky and almost catches up with Jupiter at the end of the month. Saturn is easily visible all evening, setting well after midnight. Mars is at conjunction mid June so not visible this month.
Pluto will occult a magnitude 12.2 on the morning of June 30. The event is predicted to be visible from New Zealand.
MERCURY was at inferior conjunction at the end of May, following which it moves into the morning sky. It will remain too close to the Sun to see for much of the month, but will be briefly visible in the brightening dawn sky towards the end of June.
The planet is in Taurus all month, starting June some 3.5° from the brightest star, Aldebaran. The two will then be too close to the Sun to see. Mercury moves away and up from Aldebaran until becoming stationary on June 12. Following that Mercury reverses direction and moves towards the star, with the two closest on the morning of June 24, 2° apart. With a magnitude 0.6 the planet will be a shade brighter than the star. At beginning of nautical twilight at 6.40 am when the Sun will be 12° below the horizon, the two will be a low 8° up, 30° round from east. Aldebaran will be to the right of Mercury and slightly higher.
By June 30, Mercury will have moved further to be below Aldebaran, but will have brightened to magnitude 0.0. At 7am it will again be some 8° above the horizon, only a few degrees east of northeast. Aldebaran will be 6.5° above it. The end of June will give the best chance to catch a glimpse of Mercury at its apparition in the morning sky.
VENUS sets more than 3 hours after the Sun during the June, making it readily visible to the west after sunset. Half an hour after sunset will find Venus more than 20° up in a direction well north of west. It starts the month in Gemini, but from 3rd to the 24th will be crossing Cancer. During the last few days of the month it is in Leo, closing in on Jupiter. On the 30th the two will be just over half a degree apart. They are closer still on July 1.
The crescent moon joins the party on June 20 when it will be just over 5° from Venus and a little further from Jupiter.
MARS is at conjunction with the Sun mid June. At conjunction Mars will be 232 million km beyond the Sun and 384 million km from the Earth. Mars will be within 4° of the Sun throughout June, as seen from Earth, so much too close to the Sun to see.
JUPITER is an early evening object, setting about 10 pm on June 1 and a couple of minutes after Venus on the 30th. It moves from Cancer to Leo on June 1 ahead of Venus which almost catches up with Jupiter by the end of June.
The crescent moon is closest to Jupiter on the 21st when the two will be 5.5° apart. This is one evening after the moon's approach to Venus. By June 30 Venus and Jupiter will be a brilliant pair less than 1°.
Mutual events of jovian satellites
There are about 5 mutual events of Jupiter's Galilean satellites observable from NZ during June. One occurs when Jupiter is very low. Better placed ones are:
June 1, Europa occults Io, mid event ca 8.46pm, duration 3.7 min, altitude ca 12°, az 307°. June 4, Ganymede occults Io, mid event ca 7.17pm, duration 29.1 min, altitude ca 22°, az 324°. June 6, Io occults Europa, mid event ca 6.33pm, duration 5.6 min, altitude ca 26°, az 333°. June 22, Europa occults Ganymede, mid event ca 7.25pm, duration 4.9 min, altitude ca 15°, az 309°
This is almost the end of the current series of mutual events. Useful observations and timings of these events can be made by those set up for the video observation of minor planet occultations.
Users of Dave Herald's Occult program can generate their own predictions of these and other events. Hristo Pavlov's Occult Watcher programme will also list them and has diagrams showing the satellites relative to Jupiter. Details can also be found on the IMCCE web site, http://www.imcce.fr/phemu/ where predictions and requirements for observing and reporting information are available.
SATURN is visible all evening following its May 23 opposition. It doesn't set until several hours after midnight. The planet is in Libra moving slowly in a retrograde, westerly, sense as the Earth overtakes the planet.
The moon passes Saturn twice during the month. The first occasion is on June 1 when the 98% lit moon will be 5° from Saturn at midnight. The two will be only slightly further apart at 6 pm on the 2nd. The moon will pass Saturn again on June 29. Early evening the 91% lit moon will be a little under 4° below Saturn. They will be nearly 6° apart by midnight with the moon now to the upper right of Saturn due to the rotation of the sky.
URANUS is a morning object in Pisces rising more than 4 hours before the Sun on the 1st and rather over 6 hours before it on the 31st. The planet's magnitude is 5.9 to 5.8, so readily visible in binoculars.
NEPTUNE rises just before midnight on June 1 and two hours before on June 30. The planet remains in Aquarius at magnitude 7.9. It is stationary on June 12 after which is recommences its easterly motion.
PLUTO is in Sagittarius rising near 7.24 pm on the 1st and 2 hours earlier on the 30th about 24 minutes after sunset. Its magnitude will be 14.3. On the 30th Pluto will occult a 12.2 magnitude star at about 4.52am (June 29, 16:52 UT). The predicted path of the occultation is very promising for New Zealand. Video observations and light curves are wanted!
BRIGHTER ASTEROIDS: (1) Ceres is in Capricornus most of June, it moves into Microscopium on the last day of the month. It rises just before 9pm on the 1st and at 6.41 on the 30th. On June 22 Ceres will be 12', less than half the full moon's diameter from the 4.1 magnitude star omega Cap. The asteroid will be to the left of the star
(4) Vesta is a morning object in Pisces until June 21 when it crosses into Cetus. It brightens slightly during June from magnitude 7.9 to 7.6. Vesta rises at 1.18 am on June 1 and just after midnight on the 30th.
-- Brian Loader
6. Mt John's 50th Anniversary Symposium
Mt John University Observatory celebrated its fiftieth anniversary over May 6-8, Wednesday-Friday, when Canterbury University's Department of Physics & Astronomy held a symposium at Lake Tekapo to mark the event. Nearly 80 participants came from around the world, including UK, US, France, South Africa, Japan and Australia for the event.
The opening on Wednesday evening was held in the Godley Hotel, and Associate Professor Karen Pollard (Mt John director), Prof. Mike Reid (Physics and Astronomy HoD) and Prof. Wendy Lawson (UC PVC Science) made short speeches.
Former graduate students were encouraged to return for the event, and these included Dr David Buckley (MSc 1982) from Cape Town, Prof. Gerry Gilmore FRS (PhD 1979) from Cambridge, UK, Duncan Hall from Wellington (ME 1981), Dr Phillip MacQueen (PhD 1986) from Austin, Texas, Dr Jennifer McSaveney, Wellington, (PhD 2003) and Michael Snowden (MSc 1974). In addition, past graduate students from other universities who did their thesis work at Mt John also came, including Professors Ed Guinan and George Wolf (originally from the University of Pennsylvania in the late 1960s), Dr Yvette Perrott (originally from Auckland, now in Cambridge UK) and several more. The success of Mt John has certainly come in large part from the 175 graduate students who have written theses using Mt John data, 82 of them from the University of Canterbury and the remainder from other New Zealand universities or universities overseas.
Former Mt John or Canterbury staff members included Alan Thomas, Rod Austin, Alan Gilmore, Pam Kilmartin and Dr William Tobin (from France). The founder of Mt John was Frank Bateson, who passed away 8 years ago, but his daughter Audrey Walsh came from Wollongong, NSW, and gave an inspiring talk about her father's work to establish the observatory. Another distinguished visitor from Australia was Prof. Mike Bessell from Canberra, who wrote an influential report for MORST (as it then was) on New Zealand's need for a national observatory. He talked about his report at the symposium. We also had Dr Stella Kafka from Massachusetts, the new director of the American Association of Variable Star Observers (with whom Mt John has an active collaboration with the robotic telescope), and Prof. Yasushi Muraki, one of the founders of the MOA microlensing project from Nagoya university, Japan.
The whole event was a good opportunity for people with a former connection to Mt John to rekindle old friendships and to learn more about the past research undertaken at Mt John; it was a time for reminiscences and some predictions and advice for the future. The talks took place in six sessions over a day and a half - 28 talks in all - from the site-testing days to the present, on instrumentation, discoveries, the rigours of observing on long winter nights, how in 2004 we obtained a 1.8-m telescope for microlensing and the MOA project, thanks to our collaboration with Nagoya University and a $7.5M grant from the Japanese government (obtained by Professor Yasushi Muraki). Graeme Murray from Earth & Sky discussed how Mt John was opened up to astro-tourists just over a decade ago, with the result that the observatory is now a mecca for visitors from around the world, numbering some 120,000 each year.
On Thursday evening we retired to the Godley Hotel for a sumptuous banquet, where William Tobin gave an inspired and witty after-dinner speech, followed by a beautiful song by Bex Murray (daughter of Graeme of Earth & Sky).
On the Friday afternoon we had an open day on Mt John, and this allowed everyone to see the observatory and its four telescopes and a number of instruments, including Hercules. That evening was clear, and most participants returned to Mt John for some visual observing, led by Alan Gilmore and Pam Kilmartin on the McLellan and B&C telescopes. Overall, this was a very successful celebration of half a century of New Zealand's only professional observatory for optical astronomy. Whether we can celebrate another half century in 2065 remains to be seen; currently Mt John faces numerous challenges, and its staffing levels for both academic and technical staff are now the lowest at any time in its 50-year history, with the result that innovative new research projects have all but ground to a halt.
-- john hearnshaw.
Copied from the Physics & Astronomy Department Newsletter of 15 May. See the Newsletter with Symposium group photo at http://www.phys.canterbury.ac.nz/newsletter/2015/2015-05-15.pdf
7. RASNZ Conference
The RASNZ held its annual Conference in Lake Tekapo village over the weekend of May 8-10. There were around 120 registered participants, double the usual number. Attendance was boosted by many who had come from overseas for the Mt John 50th Anniversary celebrations and stayed on for the Conference, giving it added richness.
The Canterbury Astronomical Society was the host organisation. CAS's President Euan Mason welcomed attendees at the Opening Ceremony on the Friday evening.
RASNZ President John Hearnshaw noted the conjunction of the Conference with Mt John's 50th Anniversary. It is also important in that Lake Tekapo, and the Mackenzie Country generally, are internationally known for their dark and starry skies. The Aoraki-Mackenzie International Dark Sky Reserve covers some 4300 sq.km. of the northern half of the Mackenzie Country, including Twizel and the Mt Cook region. The AMIDSR was awarded the Gold Tier status by the International Dark Sky Association for its sky quality and the District Council's protections of the sky through its lighting ordinances. In 2013 a very successful Starlight Festival was held at Lake Tekapo. Another will be held at Twizel on October 9-11 this year.
Adding to the numbers attending were ten secondary school pupils and six Canterbury University 1st Year Astronomy students. Their attendance was supported by the RASNZ to attract more young people into the Society, there being concern that its membership is aging.
Mackenzie District Council Mayor Claire Barlow opened the conference. Claire noted that the MDC has had lighting ordinances in place in the Mackenzie since 1981. These have paid off with the rise of astro- tourism. Canterbury Tourism forecasts a 'tsunami' of visitors wanting to visit the Mackenzie and see the stars. (Lake Tekapo's Earth and Sky Ltd, the biggest astro-tourism company, employ forty people now and wonder how they will cope with the projected increase.)
Karen Pollard gave the Fellows Lecture "The Music of the Stars" outlining her journey to becoming an astronomer. Now an Associate Professor in Canterbury University's Department of Physics & Astronomy, Karen's interest began in childhood as a voracious reader. She loved maths and science and one Christmas was given a telescope that her folks had bought at a garage sale. Proneness to motion sickness scotched any ideas of becoming an astronaut. Among inspirations were the planetary photos from Voyager, Carl Sagan's 'Cosmos' TV series and Douglas Adams's 'The Hitchhiker's Guide to the Galaxy' particularly its 'Don't panic' advice. Karen got her PhD at Canterbury studying RV Tauri stars: large old pulsating stars in dusty environments. Karen has been involved with MACHO, MOA and OGLE microlensing projects in NZ and South Africa. Results included identifying RV Tauri stars and Type II Cepheids in the Large Cloud of Magellan in their databases. These programmes have also shown that planets are common around most stars. Karen's husband Michael Albrow provides mathematical modelling of pulsating stars. Karen and Michael had a year in the United States when Michael worked at the Space Telescope Science institute and Karen at Gettysburg College. The study of pulsating stars has led on to astro- seismology, the study of multi-mode vibrations in stars. Analysis of these vibrations gives much information about the stars' internal structure. This work earned a Marsden grant that was completed last year.
There followed on Saturday and Sunday many talks on a wide variety of topics. The Editor will try to summarise some of them, at least, in later Newsletters. As well there were a number of posters on mostly technical aspects of observing.
At the conclusion on Sunday afternoon Euan Mason thanked the organisers, most particularly John Hearnshaw and Orlon Peterson. John praised the Tekapo Catering Company for their excellent fare and service. He also thanked the international contributors Ed Guinan, Gerry Gilmore, Stella Kafka, David Buckley, Philip MacQueen and William Tobin for travelling long distances to attend, as well as the several Australians who attended.
Next year's Conference will at Napier's Holt Planetarium, 2016 May 13- 15. Garry Sparks announced that its theme will be astrobiology. Possible side trips are to the out-of-town observatory and to see the collection of Ian Axford's medals displayed at Napier Boys' High School. The Conference dinner theme will be the electromagnetic spectrum. And don't forget your dancing shoes, Garry advised.
8. Young Star Clusters at High Galactic Latitudes
Brazilian astronomers have made a remarkable discovery: clusters of stars forming on the very edge of the Galaxy. The team, led by Denilso Camargo of the Federal University of Rio Grande do Sul in Porto Alegre, Brazil, publish their results in the journal Monthly Notices of the Royal Astronomical Society.
The Milky Way Galaxy that we live in has a barred spiral shape, with arms of stars, gas and dust winding out from a central bar. Viewed from the side, the Galaxy would appear relatively flat, with most of the material in a disc and the central regions.
Stars form inside massive and dense clumps of gas in so-called giant molecular clouds (GMCs) that are mainly located in the inner part of the galactic disc. With many clumps in a single GMC, most (if not all) stars are born together in clusters.
Denilso´s team looked at data from NASA´s orbiting Wide-Field Infrared Survey Explorer (WISE) observatory. They not only found GMCs thousands of light years above and below the galactic disc, but that one of them unexpectedly contained two clusters of stars. This is the first time astronomers have found stars being born in such a remote location.
The clusters, designated Camargo 438 and 439, are within the molecular cloud HRK 81.4-77.8. This cloud is thought to be about 2 million years old and is around 16000 light years beneath the galactic disk, in the direction of the constellation of Cetus
Denilso believes there are two possible explanations. In the first case, the 'chimney model', violent events such as supernova explosions eject dust and gas out of the galactic disk. The material then falls back, in the process merging to form GMCs.
The other idea is that the interaction between our Galaxy and its satellites, the Magellanic Clouds, may have disturbed gas that falls into the Galaxy, again leading to the creation of GMCs and stars. The chimney model would need several hundred massive stars to have exploded as supernovae over several generations, creating a 'superwind' that threw HRK 81.4-77.8 into its present position. Over millions of years, the bubbles created by the explosions may then themselves compress material, forming more stars and fuelling the ejection of material in a 'galactic fountain', where the dust and gas eventually rains back on to the disk.
-- From a Royal Astronomical Society (U.K) press release. See the original with pictures at https://www.ras.org.uk/news-and-press/2592-astronomers-find-newborn-stars-at-the-edge-of-the-galaxy
9. Mercury Mission Ends
After four years at Mercury, NASA's Messenger orbiter finished its remarkable mission and crashed into the planet on April 30. The spacecraft has been operating on borrowed time for months. Its fuel tanks nearly empty after a decade of interplanetary manoeuvring, the spacecraft could only fire its engine so many times before the pull of Mercury's gravity - coupled with the Sun's perturbing pull - forced it to crash into the planet.
Messenger's initial polar orbit around Mercury ranged in altitude from just 200 km to about 15,000 km over 12 hours. Later the orbit was adjusted so the spacecraft passed even closer. It made 4,105 orbits around Mercury.
Launched in August 2004, Messenger first became acquainted with Mercury during three close flybys in 2008-09. (The spacecraft's name, by the way, is a contraction for Mercury Surface, Space Environment, Geochemistry, and Ranging.) Messenger finally settled into orbit around the planet on 18 March 2011 UT.
The nominal mission was to be only a year, but with the spacecraft still healthy NASA managers opted to continue the mission and, in March 2014, to lower the periapse (close point) of each orbit to less than 50 km. These mission extensions, particularly moving the spacecraft closer in, paid big dividends in terms of surface photography and geochemical assays. But it also meant more frequent thruster firings to keep the spacecraft from swooping too low and striking Mercury prematurely.
One of the mission's most unexpected results is that the rocks and dust on Mercury's surface contain very little iron. This is odd because Mercury has a huge, iron-dominated core that takes up three-fourths of the planet's diameter and half its volume. So geochemists expected that the planet's surface would contain an abundance of iron-rich minerals.
This finding has a bearing on another Mercurian mystery. The planet's surface is very dark, reflecting only about 7% of the sunlight striking it. That's even darker than the Moon. Researchers have long known that the lunar surface becomes less reflective over time because tiny meteorites pepper the lunar dust, momentarily flash-melting its iron- bearing silicate minerals and creating submicroscopic bits of metallic iron. These iron particles are what make the Moon appear dark. But given Mercury's iron-poor surface, some other process must be involved.
In the March 31st issue of Nature Geoscience, a trio of researchers led by Megan Bruck Syal (Lawrence Livermore National Laboratory) offer a reasonable alternative. "One thing that hadn´t been considered was that Mercury gets dumped on by a lot of material derived from comets, Syal notes in a press release from Brown University.
She and her colleagues first estimated that the infall of comets and cometary dust over the past 200 million years could have infused the top layer of Mercurian dirt with 3% to 6% carbon. Then they conducted impact simulations at the NASA Ames Vertical Gun Range to confirm that the comet-borne carbon would actually stick around, in the form of tiny particle clusters called agglutinates.
Moreover, the resulting surface would have a very bland spectrum, exactly what Messenger found. The carbon acts like an invisible paint that has been building up on Mercury's surface for billions of years. --------
The European Space Agency is assembling the next mission to Mercury. A spacecraft called BepiColombo is to be launched in 2017 and arrive at Mercury in 2024.
BepiColombo will actually consist of two orbiters: one to study Mercury itself and the other to probe the planet's unusual magnetosphere. ESA is building one half, the Mercury Planetary Orbiter, and Japan is supplying the Mercury Magnetospheric Orbiter.
In case you're wondering, BepiColombo honours Italian researcher Giuseppe "Bepi" Colombo (1920-84). He first deduced that Mercury has a spin-orbit resonance, showing that the planet rotates three times for every two orbits it completes around the Sun. Colombo also realized that NASA's Mariner 10 spacecraft could be placed in a heliocentric orbit that synched with Mercury's - a discovery that allowed Mariner 10 to make three flybys of the innermost planet in 1974-75.
--From a Sky & Telescope website article by Kelly Beatty on 1 May. See the original with pictures and diagrams at http://www.skyandtelescope.com/astronomy-news/messenger-spacecraft-crashes-into-mercury-050120151/?et_mid=747161&rid=246399573
For a list of Messenger's scientific and technical achievements see http://messenger.jhuapl.edu/news_room/presscon14_multi.html#results
--------- "College isn't the place to go for ideas." -- Helen Keller.
"The important thing is not to stop questioning." -- Albert Einstein.
"If mankind minus one were of one opinion, then mankind is no more justified in silencing the one than the one - if he had the power - would be justified in silencing mankind." -- John Stuart Mill.