RASNZ Electronic Newsletter July 2016

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 187

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. Juno Arrives at Jupiter
2. Horowhenua StellarFest July 29-31
3. Harry Williams Astrophotography Competition
4. Replica Spacecraft Capsule Sought
5. The Solar System in August
6. Nova Scorpii 2016
7. Norman Dickie's Century Celebration
8. 2016 Conference Report - Part 1
9. A New Dwarf Planet
10. A Three-Sun Planet
11. How to Join the RASNZ
12. Quote

1. Juno Arrives at Jupiter

After a 5-year-long journey, NASA's Juno probe arrived at its destination and slipped into orbit around Jupiter.

The Juno probe fired its main engine and entered a polar orbit around Jupiter at (Earth receive time) 03:53 on July 5th Universal Time (UT). Juno carried out a scheduled 35-minute-long burn that slowed its velocity by 542 metres per second (1058 km/h), enough to become a captured satellite of Jupiter with an initial 53.5-day orbital period. Arriving at 58 km per second (209,000 km/h) with respect to the planet, Juno also performed the fastest orbital insertion to date.

All the science instruments were turned off during the crucial engine burn. Juno resumed full transmissions to Earth 58 minutes after the thruster lit up, indicating all is well with the spacecraft. At 5.8 astronomical units or 869 million km from Earth, Juno is currently more than 48 light-minutes away, with a corresponding lag time as transmissions reach NASA's worldwide Deep Space Network.

Launched on 5 August 2011, Juno took almost five years and one Earth gravitational assist flyby (on 9 October 2013) to reach Jupiter.

Juno's looping initial orbit keeps it well clear of the most intense charged-particle belt trapped around the planet. It also means that the spacecraft won't return to the planet's immediate vicinity until August 27th. On October 19th, Juno will fire its main engine one final time to drop the spacecraft into a series of tighter, 14-day-long science orbits. Juno also revved its rotation up from two to five revolutions per minute during today's orbital insertion manoeuvre. Spinning the spacecraft allows for stabilization without the use of reaction wheels. The very first spacecraft to explore Jupiter - Pioneers 10 and 11 in the early 1970s - utilized the same approach.

The mission's three major objectives are to study Jupiter's polar magnetosphere, assess the composition of its atmosphere, and probe its deep interior. To accomplish this, the spacecraft must duck under the planet's intense radiation belt and thread a target zone just above its cloud tops.

Juno will plunge closer to the Jovian cloud tops than any mission before, passing just 4,200 km away over the course of 36 orbits. Its instruments will also examine Jupiter's polar regions close up on each successive close pass.

Does Jupiter possess a solid rocky core at its heart, or are those heavy elements dissolved in a sea of metallic hydrogen all the way though? How similar is the source Jupiter's powerful magnetic dynamo to the Sun's? Juno will, for the very first time, sound the interior of our solar system's largest planet in an effort to tell the story of its current state and, perhaps, its origin and role in the formation of the solar system.

"Where is the water?" is a major question that mission scientists expect Juno to answer. NASA's Galileo probe plunged into Jupiter's atmosphere on 7 December 1995 and measured a curious lack of water. Is this paucity the norm for Jupiter's upper atmosphere, or did the probe merely hit a dry patch? Either answer has enormous implications for models of planetary formation.

The Juno probe will also test frame-dragging, as predicted by Einstein's theory of general relativity, as it maps the gravitational field of Jupiter.

To carry out its mission, Juno carries a suite of instruments:

JunoCam: The craft's sole camera will provide close-up images of the polar regions of Jupiter during each flyby. As part of an online outreach campaign, members of the public will help choose image targets for JunoCam, coordinated with an amateur observer campaign. Taking images from a spinning spacecraft is difficult, and JunoCam overcomes this using a "push broom" imaging technique, taking consecutive thin strips of images during each spin and later building them up into a single comprehensive image.

Ultraviolet Imaging Spectrograph (UVS) and Jovian Infrared Auroral Mapper (JIRAM): These imagers will study the compositions of clouds and hazes in Jupiter's uppermost atmosphere at ultraviolet and infrared wavelengths, respectively.

Radio and Plasma Wave Sensor (Waves), Jovian Energetic particle Detector Instrument (JEDI), and the Jovian Auroral Distribution Experiment (JADE): These detectors will study the interrelationship between Jupiter's atmosphere and magnetic field and chronicle auroral activity on Jupiter.

Magnetometers and Gravity Science instrument (MAG and GS): Their goal is to map the planet's magnetic and gravitational field. Microwave Radiometers (MWR): Able to penetrate deep into Jupiter's atmosphere at microwave wavelengths, MWR will map the depth and extent of atmospheric circulation. MWR will also measure the amount of water present in Jupiter's atmosphere.

Juno's instruments are contained within an enormous titanium vault, in an effort to shield them from Jupiter's extensive radiation belts. Even then, orbital precession will eventually drag the spacecraft into the deadly belts, ending the mission.

Juno is also the first spacecraft to explore the outer solar system powered not by a plutonium-fueled radioisotope thermoelectric generator (RTG), like those used on the Voyagers , Galileo, and Cassini, but by solar energy. The three solar arrays powering Juno are enormous, spanning 20 m - roughly the size of a basketball court. At five times Earth's distance from the Sun, solar energy in the vicinity of Jupiter is 1/25th of what Earth receives. Juno's enormous solar panels generate about 500 watts of energy, enough to power a small kitchen refrigerator. Half of that power goes simply to heating the core of the spacecraft.

With those large solar panels, the Juno probe must carefully thread Jupiter's powerful magnetosphere, avoiding a torrent of electrical current that sometimes reaches millions of amps. One encounter with the powerful Io plasma torus linking the innermost Galilean moon with Jupiter would doom the mission.

Radiation exposure is a very real threat to the mission. On Earth, we're exposed to about a third of a rad a year at sea level from natural background sources. Over its 1½ years of operation, Juno will be exposed to an amazing 20,000,000 rads, a lethal dose for humans many times over.

The end of mission comes on 20 February 2018, when engineers will direct Juno to burn up in Jupiter's atmosphere, avoiding any future contamination of Jupiter's large moons.

Pioneer 10 was the first spacecraft to flyby Jupiter in 1973. Other Jupiter flyby alumni include Pioneer 11, Voyager 1 and 2, Cassini, New Horizons, and Ulysses. To date, Galileo was the only other mission that entered orbit around Jupiter, operating from 1995 to 2003.

-- From an article by David Dickinson on Sky & Telescope's webpage.

For the full text and images see http://click.e.skyandtelescope.com/?qs=b1f48361929dd83ee32365862d9a0e217614bb563e347abb50f675c237311742e47e31288b74f9bc.

More information on the Juno mission: http://www.nasa.gov/juno Follow the mission on Facebook and Twitter: http://www.facebook.com/NASAJuno http://www.twitter.com/NASAJuno

2. Horowhenua StellarFest July 29-31

Steve Chadwick, President, Horowhenua Astronomical Society, writes:

This is just to let you know that our annual StellarFest is being held on the weekend 29th-31st July. Information and how to book can be found here: http://www.horoastronomy.org.nz/upcoming-events/stellarfest

We are still putting the programme together so please keep checking back for updates. For the best accommodation please book early.

3. Harry Williams Astrophotography Competition

Calling all Astrophotographers, it's that time of year again, time to get your entries in for the 2016 Harry Williams Astrophotography competition, this year we are very lucky to have Phil Plait the "Bad Astronomer" as our judge, Phil is best known for debunking misconceptions in Astronomy but is also a well-known Astrophotography enthusiast, he received his PhD in Astronomy at the University of Virginia in 1994, during the 1990s, Plait worked with the COBE satellite and later was part of the Hubble Space Telescope team at NASA Goddard Space Flight Center, working largely on the Space Telescope Imaging Spectrograph. In 1995, he published observations of a ring of circumstellar material around a supernova (SN 1987A), which led to further study of explosion mechanisms in core-collapse supernovae.

This year the Solar System and Miscellaneous/Artistic categories will be sponsored by the Australian Sky and Telescope magazine, winners of these two categories will receive a 12 month subscription to the magazine as well as a cash prize, in addition to the usual Auckland Astronomical Society certificate all entries that either win a category or are highly commended will also have their image printed in the Australian Sky and Telescope magazine, further prizes and sponsors to be announced soon.

This year, the entries to the Harry Williams Astrophotography competition must be in by the 31st of August, so please don't delay to get those entries in, as we can't accept late entries, entry forms and the competition rules can found on the front page of the Auckland Astronomical Society's website http://www.astronomy.org.nz/. The winners of the competition will be announced at the Auckland Astronomical Societies annual Burbidge Dinner which will be held on Saturday 8th October at Alexandra Park. The Guest speaker will be Dr Doug Simons, Executive Director of the Canada-France-Hawai'i Telescope (CFHT) on Mauna Kea in Hawaii so it should make for a great night out! We are looking forward to seeing all your entries and good luck with the competition.

-- Jonathan Green's note to nzastronomers Yahoo group.

4. Replica Spacecraft Capsule Sought

Lloyd Esler is looking for a replica spacecraft capsule that is capable of accommodating a child. No, not the last desperate hope of a harassed parent, but an educational item suitable for taking around schools.

Lloyd is also looking for a set of Cornflakes space-themed plastic toys from the 1960s. He remembers Sputnik, Telstar and the Mercury capsule.

Anyone with suggestions please contact Lloyd Esler This email address is being protected from spambots. You need JavaScript enabled to view it. P. 03 213 0404.

5. The Solar System in August

Dates and times shown are NZST (UT + 12 hours) unless otherwise stated. Rise and set times are for Wellington. They will vary by a few minutes elsewhere in NZ.

Sunrise, sunset and twilight times in august

                          August  1  NZST                  August 31  NZST
                Morning      evening           morning      evening
SUN:         rise: 7.26am,  set: 5.28pm     rise: 6.45am,  set: 5.57pm
Twilights
 Civil:    starts: 6.59am, ends: 5.56pm   starts: 6.20am, ends: 6.23pm
 Nautical: starts: 6.26am, ends: 6.29pm   starts: 5.48am, ends: 6.55pm
 Astro:    starts: 5.53am, ends: 7.01pm   starts: 5.16am, ends: 7.27pm

June phases of the moon (times as shown by guide)

          New moon:      August  3 at  8.45 am (Aug  2, 20:45 UT)
  First quarter: August 11 at  6.21 am (Aug 10, 18:21 UT)
  Full moon:     August 18 at  9.27 pm (09:27 UT)
  Last quarter   August 25 at  3.41 pm (03:41 UT)

The planets in august

August is a month of planetary conjunctions. All the planets are visible at some time in the evening sky.

Mercury, venus and jupiter, early evening objects

Towards the end of August a fine grouping of the three planets will be visible in the early evening sky as the sky darkens following sunset. Between August 18 and 22 Mercury will be about 4° to the left of Jupiter. On the 18th Jupiter will be a little higher then Mercury. Over the next few evenings Jupiter will move down and become the lower of the two. Venus will be a few degrees below the pair.

Over the following evenings Venus will close in on Jupiter. On the 27th it will be 42 arc minutes below Jupiter, the following evening Venus is 19 minutes above Jupiter. Mercury, at magnitude 0.9 nearly 3 magnitudes fainter than Jupiter, will 5° to the left of the pair and a little higher.

At their closest just before midday, NZST, on the 28th, the two planets will be about 4 arc minutes apart. In NZ skies they are about 32° up at an azimuth of 52°, i.e. 52° from north round to east. In a clear sky Venus should be readily visible in binoculars or a small telescope. Having found Venus, Jupiter, about 2 magnitudes fainter, should be visible at least in a small telescope. The pair will be some 22° from the Sun.

On the 29th Venus is at its closest to Mercury. The two will be some 5° apart with Jupiter 1.3° below Venus. The line from Venus to Jupiter is almost at right angle to the line from Venus to Mercury.

The moon passes the three planets early in the month. For NZ it is closest to Venus on the evening of the 4th, when the very thin crescent moon, Venus and Regulus will form a triangle, just over 2° on each side. The moon is 3° above Mercury on the 5th and half a degree from Jupiter on the 6th. The moon occults both Mercury and Jupiter this month, but neither events are visible from NZ.

For good measure Venus is about a degree from Regulus, magnitude 1.4, on August 5 and 6.

Mars, saturn and antares

Not to be outdone, Mars and Saturn are also in conjunction towards the end of August. They are at their closest on the 24th, with Mars between Saturn and Antares. Mars, brightest at magnitude -0.4, will be 1.8° from Antares, mag 1.0, with Saturn, mag 0.4, in the opposite direction. The three will be easily seen all evening, they don't set until well after midnight.

Mars, moving quite rapidly, starts August in Libra but crosses into Scorpius on the 2nd. Its path takes it between delta and pi Sco (mags 2.3 and 2.9 respectively) on the 9th and 10th. As it passes between Saturn and Antares in the fourth week of August, Mars will cross a corner of Ophiuchus before returning to Scorpius on the 27th.

Saturn, in Ophiuchus, is stationary on the 13th so its position changes very little during the month.

The moon, a day after first quarter will join the group on the 12th. It is closer to Saturn, the two about 4.5° apart during the evening.

Outer planets

URANUS, at magnitude 5.8, is in Pisces. It rises nearly half an hour before midnight on August 1 and by 10 pm later in the month.

NEPTUNE rises at 8am on the 1st and as the Sun sets on the 31st. (Opposition is on September 2). The planet is at magnitude 7.8.

PLUTO at magnitude 14.3 is also in the evening sky during August setting well after midnight. The planet remains in Sagittarius. Late in the month it will be just under half a degree north of the 3.7 magnitude star omega Sgr.

Minor planets

(1) CERES is in Cetus during August and brightens from magnitude 8.9 to 8.4. It is essentially a morning object, although it will rise just after 10 pm on the 31st.

(2) PALLAS starts August at magnitude 9.4 in Pegasus. It then rises at 8pm. Its retrograde motion takes Pallas into Equuleus on August 21 having been at opposition on August 13 at magnitude 9.2.

(4) VESTA rises close to 5 am on August 1. It is in then the most northerly part of Orion some 15° north of Betelgeuse. By the 7th it will have moved on into Gemini. At the end of August, Vesta will rise just before 4am. Its magnitude is 8.5 to 8.4.

-- Brian Loader

6. Nova Scorpii 2016

Nova Scorpii 2016 was discovered by Hideo Nishimura (Kakegawa, Shizuoka-ken, Japan) and reported by S. Nakano, Sumoto, Japan, via CBET 4285). The nova was discovered 2016 June 10.629 UT. The discovery magnitude was 12.4.

At the time this newsletter is being published the outburst will be about 40 days old. The nova is fading steadily, so in future months observers with larger aperture telescopes are encouraged to follow the event. At time of publication the nova is approximately Visual 13.7

Information on some early observations of Nova Sco 2016 - colour band observations and spectral characteristics indicating a Fe II nova - are given in the latest Variable Star South (VSS) newsletter. This issue of the newsletter will be posted on the VSS website at the time of the publication of the RASNZ newsletter or soon after. Go to http://www.variablestarssouth.org/, At top of window, Menu Bar:- Community, Select Newsletters. Alternatively use the Search box, Newsletter.

-- Alan Baldwin (RASNZ, VSS)

7. Norman Dickie's Century Celebration

Norman Dickie of Gore, an RASNZ member for 71 years, turns 100 on Sunday 2nd October. Celebrations are planned over the weekend.

The first will be on Saturday 1st at Washpool farm where Norman was born, brought up and farmed. The farmhouse owners have kindly agreed to host an afternoon tea and an evening BBQ in honour of Norman. This gathering is open to friends and relatives who come afar, including astronomers, and invited locals. The 8 km drive to the farm departs from the St Andrews Presbyterian Church in Ardwick Street at 2:00pm. This is an opportunity for those outside the Gore district to meet Norman personally as this might not be possible on Norman´s big day on Sunday. Between the afternoon tea and evening BBQ there will be a tour of Norman´s former farm.

On Sunday morning there will be a church service at 10:00am (not just for Norman) at St Andrews. Afterward a finger-food lunch will be held in the church hall. Then back into the church again for a musical concert and tributes to Norman. This is an open public event for anyone keen to attend Norman´s 100th.

Please RSVP for the Saturday afternoon tea and evening BBQ by Monday 26th September for catering purposes. No RSVP is necessary for the Sunday event at the St Andrews Church as this is an open event where hundreds of people are expected.

Contact Ross Dickie, phone (03) 208 9623, mobile 027 208 9623, This email address is being protected from spambots. You need JavaScript enabled to view it. for RSVP and further details.

8. 2016 Conference Report - Part 1

The weekend of 20-22 May 2016 saw the Royal Astronomical Society of New Zealand have its annual conference in Napier. Originally planned to be held again in the War Memorial Conference Centre after the success of the last Napier Conference, changes were forced when earthquake strengthening work ruled out its availability. The conference was shifted to the nearby Museum Theatre Gallery and to Napier Boys' High School for the Saturday night Banquet dinner.

The Hawkes Bay region turned on some really lovely weather with warm days throughout the conference.

Prior to the conference opening there were the usual round of meetings with the outgoing Council meeting for the last time before handing over to the newly elected council on Sunday. Of special note were the standing down of Rory O'Keefe who had been Secretary of the Society for six years and Gordon Hudson who was relinquishing his position as council member while remaining the society archivist.

The Affiliated Societies later met for their discussions while the Standing Conference Committee held a parallel meeting.

The conference was opened by Professor John Hearnshaw as RASNZ president and Gary Sparks, Hawkes Bay Astronomical Society president. The Honourable Stuart Nash, MP for Napier then gave an opening address. This was notable for his showing off his antique Astrolabe from the Middle East and his plea for some help in understanding how it was supposed to work!

Following on from this Professor Sergei Gulyaev (AUT) gave his presentation on the recent "Discovery of the source of high-energy neutrinos" which had recently been published in Nature. This year's Fellows' Lecture was given by the most recently elected Fellow Brian Loader. Speaking on "Pluto, 2015 June 29" he discussed his interest in occultations and the results from the Pluto occultation which occurred just prior to the arrival of the New Horizons spacecraft early last July. The occultation passed directly across NZ and gave some surprising results, among which were a still thickening atmosphere, new structure to the atmosphere, an updated diameter measurement and a final accurate position of Pluto to help refine the flyby.

Saturday morning started with a Poster mini-session with John Drummond speaking briefly about the astrophotography competition and Ana Snjegota on "Detecting forward scattering radio signals from atmospheric meteors using low-cost software defined radio". Ashna Sharan spoke on her "Microlensing modelling using nested sampling" to analyses MOA observational data, leading a session largely featuring Auckland University. Auckland undergraduate students Georgie Taylor and Mason Ng spoke jointly on "Modelling the spectra of hot stars". John Bray spoke on his ongoing work regarding "Is the link between the observed velocities of neutron stars and their progenitors a simple mass relationship?"

We then had presentations from two of the "Students with a Passion for Astronomy" (SWAPA) give their own presentations which were of a very high standard. Anushka Kharbanda spoke about quasars and Annabelle Ritchie talked about her work towards radio observations of Jupiter and broadcasting over the internet.

The next session started with Sergei Gulyaev informing us on "Activies at the radio astronomical observatory at Warkworth" and detailing the recent developments there.

Warwick Kissling gave us all an update on "Is the Solar system stable?" looking at the chaotic nature of the planets' orbits. Gary Sparks showed us "Halley's Comet World Tour: A Philatelic Odyessy" a whirlwide tour of stamps he'd collected.

This year's conference had as its guest keynote speaker a former University of Canterbury astronomy student Dr Michele Bannister from the University of Victoria, British Columbia, Canada. She spoke on the "New Discoveries in the Outer Solar System" detailing her research in the field of bodies in the outer solar system and the now substantial observations recording many new objects in the Kuiper belt and beyond. After the conclusion of the conference Michele gave a public lecture on "Pluto: Once a Point of Light, Now a World" which was very well attended and covered all the latest on what had been sent back and so far learned from the New Horizons probe flyby of the Pluto system.

After lunch Maria Pozza gave a skype talk on "New Zealand and the need for Space Law". John Hearnshaw spoke on his work with IAU commission C4 and UNESCO "The Astronomy and World Heritage Initiative" looking at preserving the world's significant astronomical sites and observatories. Bethany Jones from Hawkes Bay gave us her medical insight into "The effects of space travel on human physiology" detailing the many issues and challenges that we still face in manned space exploration.

Liam McClelland spoke on "Helium stars: Towards an understanding of Wolf-Rayet Evolution". The session was closed out by two more SWAPA students, with an impassioned talk by Finlay Mably on the Young Stars astronomy group in Christchurch and Joshua Daglish spoke on his experiences in astronomy to date and a visit he made to Mt John Observatory.

Following on was the AGM where the new Council was elected, Jennie McCormick (MNZM) was elected to the Fellowship of the Society and Professor Gerry Gilmore was honoured by the Society to become an Honorary member for his achievements.

The banquet dinner had as the theme "The Electromagnetic spectrum" which resulted in some very colourful costumes being on show. The dinner was fantastic and well catered for with a turnout of about 100. During the evening a number of awards and announcements were made. These included the awarding of the Murray Geddes Prize to Dave Cochrane of Kiwistar Optics at Callaghan Innovation. This optics group have a long history in the development and creation of various astronomical optics including the Kiwispec spectrograph, based on the Hercules design used at Mt John Observatory. Most recently Dave has been working on the Prime focus corrector for the William Herschel telescope at La Palma Observatory, one of the largest lenses ever made in the world.

The after dinner speaker was Gary Sparks who gave a very entertaining talk on Archeoastronomy in Peru covering the various sites both well- known and not so well travelled with tales of what many of these sites would have looked like in their prime and the importance of these sites in the various regions in Peru.

-- Orlon Petterson

The second part of Orlon's article will be in the August Newsletter.

9. A New Dwarf Planet

An international team of astronomers have discovered a new dwarf planet orbiting in the disk of small icy worlds beyond Neptune. The new object is roughly 700 km in size and has one of the largest orbits for a dwarf planet. Designated 2015 RR245 by the International Astronomical Union's Minor Planet Center, it was found using the Canada-France-Hawaii Telescope on Maunakea, Hawaii, as part of the ongoing Outer solar system Origins Survey (OSSOS).

"The icy worlds beyond Neptune trace how the giant planets formed and then moved out from the Sun. They let us piece together the history of our solar system. But almost all of these icy worlds are painfully small and faint: it's really exciting to find one that's large and bright enough that we can study it in detail," said Dr Michele Bannister of the University of Victoria in British Columbia, who is a postdoctoral fellow with the survey.

National Research Council of Canada's Dr JJ Kavelaars first sighted RR245 in February 2016 in the OSSOS images from September 2015. "There it was on the screen -- this dot of light moving so slowly that it had to be at least twice as far as Neptune from the Sun," said Bannister.

The team became even more excited when they realized that the object's orbit takes it more than 120 times further from the Sun than Earth. The size of RR245 is not yet exactly known, as its surface properties need further measurement. "It's either small and shiny, or large and dull," said Bannister.

The vast majority of the dwarf planets like RR245 were destroyed or thrown from the solar system in the chaos that ensued as the giant planets moved out to their present positions: RR245 is one of the few dwarf planets that has survived to the present day --- along with Pluto and Eris, the largest known dwarf planets. RR245 now circles the Sun among the remnant population of tens of thousands of much smaller trans-Neptunian worlds, most of which orbit unseen.

Worlds that journey far from the Sun have exotic geology with landscapes made of many different frozen materials, as the recent flyby of Pluto by the New Horizons spacecraft showed.

After hundreds of years further than 12 billion km (80 astronomical units, AU) from the Sun, RR245 is travelling towards its closest approach at 5 billion km (34 AU), which it will reach around 2096. RR245 has been on its highly elliptical orbit for at least the last 100 million years.

As RR245 has only been observed for one of the seven hundred years it takes to orbit the Sun, where it came from and how its orbit will slowly evolve in the far future is still unknown; its precise orbit will be refined over the coming years, after which RR245 will be given a name. As discoverers, the OSSOS team can submit their preferred name for RR245 to the International Astronomical Union for consideration.

Current orbital elements for 2015 RR245: a = 81.44 AU, q = 33.69 AU, e = 0.5863, P = 735 years, H = 3.8.

For text & images: http://www.cfht.hawaii.edu/en/news/NewDwarfPlanet/. For an animation of the early Solar System chaos model see http://www.bing.com/videos/search?q=nice+model+solar+system+formation&view=detail&mid=78DB1F448E6068C679E278DB1F448E6068C679E2&FORM=VIRE

-- From a Canada-France-Hawaii Telescope and the University of British Columbia press release forwarded by Karen Pollard.

10. A Three-Sun Planet

A team of astronomers have imaged the first planet ever found in a wide orbit inside a triple-star system. The orbit of such a planet had been expected to be unstable, probably resulting in the planet being quickly ejected from the system. But somehow this one survives. This unexpected observation suggests that such systems may actually be more common than previously thought. The results were published online in the journal Science on 7 July 2016.

The planet was discovered by a team of astronomers led by the University of Arizona, using direct imaging at European Southern Observatory´s Very Large Telescope (VLT) in Chile. The planet, HD 131399Ab, is unlike any other known world. It orbits around the brightest of the three stars in the triple system. The other two stars are a closer binary pair far from the brightest star. The planet's orbit is by far the widest known within a multi-star system. Such orbits are often unstable, because of the complex and changing gravitational attraction from the other two stars in the system, and planets in stable orbits were thought to be very unlikely.

Located about 320 light-years from Earth in the constellation of Centaurus, HD 131399Ab is about 16 million years old, making it also one of the youngest exoplanets discovered to date, and one of very few directly imaged planets. With a temperature of around 580 degrees Celsius and an estimated mass of four Jupiter masses, it is also one of the coolest and least massive directly-imaged exoplanets.

For about half of the planet´s orbit, which lasts 550 Earth-years, three stars are visible in its sky. The fainter two are always much closer together. Their apparent separation from the brightest star, seen from the planet, changes throughout the planet's 'year'.

Kevin Wagner, who is a PhD student at the University of Arizona, identified the planet among hundreds of candidate planets and led the follow-up observations to verify its nature. The planet also marks the first discovery of an exoplanet made with the SPHERE instrument on the VLT. SPHERE is sensitive to infrared light, allowing it to detect the heat signatures of young planets, along with sophisticated features correcting for atmospheric disturbances and blocking out the otherwise blinding light of their host stars.

Repeated and long-term observations will be needed to precisely determine the planet's trajectory among its host stars. However, observations and simulations so far suggest that the brightest star is eighty percent more massive than the Sun. It is dubbed HD 131399A. The less massive stars, B and C, are about 10 AU apart, a distance roughly equal to that between the Sun and Saturn. The brightest star and the close pair are about 300 AU apart. (1 AU is Earth's distance from the Sun.)

The planet travels around the star A in an orbit with a radius of about 80 AU, about twice as large as Pluto´s in the Solar System. That brings it to about one third of the separation between star A and the B/C star pair.

The authors point out that a range of orbital scenarios is possible, and the verdict on the long-term stability of the system will have to wait for planned follow-up observations that will better constrain the planet´s orbit. Computer simulations show that this type of orbit can be stable, but a small change makes it unstable.

Planets in multi-star systems are of special interest to astronomers and planetary scientists because they provide an example of how the mechanism of planetary formation functions in these more extreme scenarios. While multi-star systems seem exotic to us in our orbit around our solitary star, multi-star systems are in fact just as common as single stars.

See the original ESO press release, with picture at http://www.eso.org/public/news/eso1624/

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

11. 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 2016 year starts at $40 for an ordinary member, which includes an electronic subscription to our journal 'Southern Stars'.

12. Quote

"A university is not a 'safe space'. If you need a safe space, leave, go home, hug your teddy & suck your thumb until ready for university." -- Richard Dawkins defending free speech in academia.

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