RASNZ Electronic Newsletter March 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 183

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. RASNZ Conference Reminder
2. Notice of Annual General Meeting
3. Affiliated Societies' Committee Meeting 2016
4. RASNZ Conference Auction
5. The Solar System in April
6. Surprise Meteor Shower on New Year's Eve
7. Weak Meteor Shower March 28-29?
8. Super Luminous Supernova 2015LH
9. A Brief History of the Dominion Observatory
10. Most Distant Galaxy Seen
11. Radio Astronomy's 70th Anniversary
12. Head-on Collision Made Moon
13. Old Stars´ Fossil Fields
14. How to Join the RASNZ
15. Previously Unknown Cluster of Nothingness Discovered

1. RASNZ Conference Reminder

It is now only two months out from the RASNZ Conference, to be held May 20th-22nd in Napier. We encourage all RASNZ members (and their friends in local Societies) to come to the conference, which this year features Dr Michele Bannister, an ex-pat Kiwi and planetary astronomer, who will be talking about the recent discoveries at Pluto made by the New Horizons spacecraft. For those interested, the conference will be followed on May 23rd-24th by an astrophotography workshop.

There is still room in the conference programme for more talks (and posters), so if you have done anything astronomically interesting recently we would love to hear from you.

Details of the conference, with links to the registration and paper submission pages are to be found at http://www.rasnz.org.nz/

-- Warwick Kissling, RASNZ Standing Conference Committee.

2. Notice of Annual General Meeting

The 93rd Annual General Meeting of the Royal Astronomical Society of New Zealand will be held on Saturday 21 May 2016 at the Museum Theatre Gallery, Hawkes Bay. The meeting will begin at 4pm. Notices of motion are invited for the AGM and should reach the Secretary by 9 April 2016 to be included on the agenda.(This email address is being protected from spambots. You need JavaScript enabled to view it.) Items for the agenda include the Society´s Annual Report and the completion of the election of officers and council members. The nomination period for council has closed but there has been no nomination for secretary. Nominations can be accepted from the floor at the AGM. The minutes of the 2015 AGM are available on the RASNZ website. A full agenda for the AGM will be published after 9 April 2016. -- Rory O´Keeffe, Secretary, RASNZ

3. Affiliated Societies' Committee Meeting 2016

The Affiliated Societies Committee Meeting will be held on Friday 20 May 2016 at 4 pm. The venue is yet to be announced. Normally the meeting is attended by the President of Affiliated Societies or their nominated representative. Affiliated societies are invited to notify the secretary about their attendance and the names of the representatives who will be attending. The minutes of the previous meeting are available on the RASNZ website. The business of the meeting will include the election of the Affiliated Societies Representatives on the council of RASNZ. Any items affiliated societies would like to place on the agenda should be forwarded to the secretary at This email address is being protected from spambots. You need JavaScript enabled to view it..

-- Rory O´Keeffe, Secretary, RASNZ

4. RASNZ Conference Auction

It is planned to hold an auction of astronomical paraphernalia at the RASNZ conference banquet on 21 May. If any members of the Society have objects they would like to dispose of at the auction, could they please email the Society president, Prof John Hearnshaw (This email address is being protected from spambots. You need JavaScript enabled to view it.). The proceeds from the auction will all go to the Society, first to fund the prizes in the planned Astroquiz at the conference, and if there are surplus funds beyond that, they will be added to the Graham Blow fund that supports the competition `Students with a Passion for Astronomy´, whereby students are supported to come to the RASNZ conference.

The number of items to be auctioned will be limited to 2 or 3, and I will make a selection of the most interesting and tantalizing.

Those donating items should bring them to Napier; or, if that is not possible, then full details and photographs should accompany your email.

Please contact me by May 10 with your entries for the auction.

-- John Hearnshaw, President, RASNZ

5. The Solar System in April

NZDT ends on Sunday April 3 at 3am, clocks should then be set back one hour. Dates and times shown are NZDT (UT + 13 Hours) up to the change and then as NZST (UT + 12 hours) unless otherwise stated.

Rise and set times for Wellington. They will vary by a few minutes elsewhere in NZ.

Sunrise, sunset and twilight times in april

                        April  1  NZDT                   April 30  NZST
              morning       evening          morning        evening
SUN:         rise: 7.34am,  set: 7.14pm     rise: 7.04am,  set: 5.30pm
Twilights
 Civil:    starts: 7.09am, ends: 7.40pm   starts: 6.38am, ends: 5.57pm
 Nautical: starts: 6.37am, ends: 8.12pm   starts: 6.06am, ends: 6.30pm 
 Astro:    starts: 6.05am, ends: 8.44pm   starts: 5.33am, ends: 7.02pm

April PHASES OF THE MOON (times as shown by GUIDE)

          Last quarter:  April  1 at  4.17 am (Mar 31, 15:17 UT)
  New moon:      April  7 at 11.24 pm (11:24 UT)
  First quarter: April 14 at  3.59 pm (03:59 UT) 
  Full moon:     April 22 at  5.24 pm (05:24 UT) 
  Last quarter   April 30 at  3.29 pm (03:26 UT)

The planets in April

Jupiter will dominate the evening sky particularly early and late in the month when the moon is absent. Mercury is likely to be lost in evening twilight, setting soon after the Sun. Mars and Saturn will be to the east later in the evening, with Mars brightening to magnitude - 1.5 during the month. Venus is rather low in the dawn sky.

MERCURY is nominally in the evening sky in April but virtually unobservable. On the 1st it sets about 20 minutes later than the Sun, on the 30th about 26 minutes later. At its greatest, mid month, when the planet is at its greatest elongation 20 ° east of the Sun, it sets later.

VENUS is a low object in the morning sky in April. On the 1st it will be about 16° up as the Sun rises just north of east. By the end of the month it will be only 8.5° at sunrise, so a low but not impossible object to spot shortly before the Sun appears.

Uranus will be less than a degree to the lower left of Venus on the morning of the 23rd, but with a magnitude of 5.9 it is very doubtful the fainter planet will be visible in binoculars in the twilight.

The moon, as a very thin crescent, will be 7° above Venus on the morning of the 6th, the following morning the moon will be a similar distance below Venus. As a hair line crescent, less than 1% lit, the moon will be very difficult to spot.

MARS brightens during April by a magnitude from -0.5 to -1.5 as its distance from the Earth decreases leading up to its opposition in May. The planet rises at 9.40 pm (NZDT) on the 1st and 6.40 pm (NZST) on the 30th so by then is visible most of the night.

The planet starts April in Scorpius, 6° from Antares. It crosses into Ophiuchus on the 3rd when it will be some 8.5° from Saturn. But on the 17th Mars is stationary and then starts moving back to the west to cross back into Scorpius on the last day of the month. As a result it remains quite close to the similarly coloured Antares all month.

The moon, just past full, is closest to Mars on the 25th, when Mars, Saturn and the moon will form a near equilateral triangle with Mars at the upper apex.

JUPITER, having been at opposition early March, will be a prominent evening object throughout April. It will be in Leo moving slowly to the west towards Regulus, with the star 15° to the left of the planet as seen in the evening sky.

The moon and Jupiter will be closest on June 18, when the 87% lit moon will be about 3° from Jupiter mid evening.

SATURN will rise about 10.15 pm on the 1st, advancing to 7.20 pm on the 30th. It will not set until after sunrise. The planet remains in Ophiuchus heading slowly to the west towards Mars. The two are closest mid month when about 7° apart.

As noted for Mars, the moon will form a triple with the two planets on the evening of the 25th. In fact the moon is closest to Saturn on the morning of the 26th with the two 4° apart shortly before sunrise.

Outer planets

URANUS is at conjunction on the far side of the Sun on April 9, so will not be observable during April. At conjunction Uranus will be 20 arc-minutes south of the Sun's limb. Distance wise it will be 20.0 AU from the Sun and 21 AU (3137 million km) from the Earth.

By the end of April Uranus will rise 90 minutes before the Sun and will be 8° above Venus. The two are closest on the morning of April 23.

NEPTUNE, in the morning sky, starts April some 8° above and a little to the left of Venus. By the end of the month the two will be about 50° apart, due to the rapid motion of the inner planet. Neptune will then rise close to 2 am.

On the morning of April 5, Neptune will be 3.5° to the lower right of the crescent moon.

PLUTO at magnitude 14.4 rises just after midnight at the beginning of April and about 9.35 pm on the 30th. The planet remains in Sagittarius. It is stationary on April 18 and is about 1° from the 2.9 magnitude star pi Sgr.

Minor planets

(1) Ceres, magnitude 9.2, starts April in Aquarius just under 7° to the right of Venus in the dawn sky. It crosses into Cetus on the 2nd where it soon falls behind Venus. This in fact means it gets steadily higher in the morning sky and will rise at 4 am by April 30.

(4) Vesta, magnitude 8.4, is in Aries until the 30th when it moves into Taurus. It sets 90 minutes after the Sun on the 1st, less than an hour later on the 30th.

The 5% lit crescent moon will be just over 1° to the right of Vesta on April 9. At 6.30 pm the two will be 8° above the horizon as seen from Wellington. Vesta will be about level with the upper lit cusp of the moon.

-- Brian Loader

6. Surprise Meteor Shower on New Year's Eve

"In a way, the shower helped chase bad spirits away," says SETI Institute meteor astronomer Peter Jenniskens. "Now we have an early warning that we should be looking for a potentially hazardous comet in that orbit."

In September of 2014, Jenniskens teamed up with Professor Jack Baggaley of the University of Canterbury in Christchurch, New Zealand, to establish a meteor video surveillance project in the southern hemisphere to find such warning signs of dangerous comets. This project was similar to the existing cameras for Allsky Meteor Surveillance network (CAMS) in northern California. The CAMS network is sponsored by, and supports the goals of, the NASA Near Earth Object Observation program.

Now, 32 video cameras are spread over two stations on New Zealand´s South Island. Amateur meteor astronomers Peter Aldous at Geraldine and Ian Crumpton at West Melton are operating the stations. Data are submitted to the SETI Institute where Jenniskens calculates the meteoroid trajectories.

"New Zealand, lying between 35 and 47 degrees southern latitude, has a long tradition of meteor studies," says Baggaley. "While radar observations in the past were efficient at observing sporadic meteors, the video cameras can see the meteor showers really well."

Jenniskens and Baggaley describe the network and report on the new result in a paper submitted for publication in the Journal of the International Meteor Organization. The paper characterizes the trajectories of 21 Volantids measured on December 31, and two more on January 1.

"These were naked-eye meteors and rates peaked at the time of the local New Year´s Eve celebrations," notes Jenniskens. "One out of three meteors that night came from this shower." The shower was not seen the year before and is not known from past radar observations.

"A confined stream of dust particles must have been steered into Earth´s path for a brief moment," says co-author and meteoroid stream dynamicist Rachel Soja of the University of Stuttgart, Germany, who calculated that the Earth will be safe from the comet and its debris in the near future.

The meteoroids move in a fairly steeply inclined orbit similar to that of some Jupiter-family type comets. "The parent body of this stream still eludes us," says Soja. "It may not be active now and the high inclination may make it difficult to spot."

-- A SETI Institute press release. See the original at http://www.seti.org/seti-institute/press-release/surprise-meteor-shower-new-years-eve

7. Weak Meteor Shower March 28-29?

Peter Jenniskens of the SETI Institute and NASA Ames Research Center; and J. Vaubaillon, Institut de Mecanique Celeste et de Calcul des Ephemerides, Paris, report that, in the wake of the close 0.0356-AU approach of comet 252P to the earth on Mar. 21, it is possible that a new meteor shower will appear on Mar. 28 and 29. A standard model was developed by integrating the orbit of the comet back to A.D. 1850 and ejecting dust at each perihelion passage since that time. After forward-integrating these particles to March 2016, it was found that at no time this year are the densest dust trail sections in the earth's path. Instead, a diffuse cloud of perturbed meteoroids ejected during 1894-1926 is calculated to be in the earth's path between Mar. 28.0 and 29.417 UT. Dust ejected in 1921 is predicted to peak Mar. 28.5 and 28.958 UT, respectively), while dust from 1915 would peak at March 28.75. Slow meteors will radiate from a geocentric radiant at R.A. = 5h08m, Decl. = -16.3°, with velocity 11.1 km/s. Rates will be low.

-- From Central Bureau Electronic Telegram 4267, 2016 March 17.

See last month's Newsletter for more on Comet 252P.

8. Super Luminous Supernova 2015LH

On 14 June 2015 the All Sky Automated Survey for Supernova (ASAS-SN) found a possible new transient in the southern constellation Vela (J2000 RA 22h02m15s, -61°39'35"). Seeing it in the raw candidates list I obtained the first confirmation image at 09:07 UT on 16th June with the 30cm Meade lx200 at Mount Vernon Observatory in Nelson. Around 100 minutes later we obtained a second confirmation image with the 1-metre LCOGT telescope at Cerro Tololo in Chile. We then put out an astronomers telegram (Atel 7642).

Analysing previous data we find that the transient was first detected on May 8 and peaked on June 5 at magnitude 16.9. Spectra obtained by several large telescopes including the SALT 10-metre and Clay 6.5- metre show a redshift of 0.2326 which indicates a distance of 3.8 billion light years. This yields an absolute magnitude of -23.5 and bolometric luminosity of 2.2 x 10^38 Watts or 5.72 x 10^11 times the Sun's output. This makes 2015LH the most luminous SN ever discovered. Although current models struggle to explain the huge output of this object follow-up observations continue to support its distance and hence energy output. A more detailed paper will follow in 'Southern Stars'.

We thank SALT staff for assistance with observations, LCOGT for continued support, the ASAS-SN team in particular Subo Dong (Peking University), and David Victor for loan of 30cm telescope. For more information on the ASAS-SN project visit their home page: www.astronomy.ohio-state.edu/~assassin/

-- Brent Nicholls, Mount Vernon Observatory, Nelson.

9. A Brief History of the Dominion Observatory

After seeing Gordon Hudson's note in Newsletter No. 180, 20 December 2015, Dr Robin Adams kindly provided the following brief history of the Dominion Observatory.

"I was most interested to read in the Newsletter Gordon's plea for help with storage space. Naturally, I cannot help with that, but I was most interested in the notes about the Dominion Observatory, and would like to offer some comments of my own - there is a lot of information in an unattributed article (by George Eiby, no less) in Report No 161 of Geophysics Division of DSIR, published in 1980, commemorating the Division's first 25 years, 1951-76.

The original transit room, octagonal clock room and small office were completed in 1907, when the New Zealand Time Service, originally set up in 1864 on the waterfront, moved there from a site near Bolton Street Cemetery. The Time Service was originally run by Archdeacon Arthur Stock and from 1887 by Thomas King. When King retired in 1911 he was succeeded by my grandfather C E Adams, with the title Government Astronomer (his full name was Charles Edward Adams, but in the family he was known as Ted - he didn't gain his doctorate till 1917).

The site was that of the Gardens Battery, fortifications erected during the Russian scare of the 1890s - not the First World War. As seismology grew in significance the Time Service became incorporated in the Seismological Observatory (and my Grandfather became Government Astronomer and Seismologist), which in turn became part of the newly- formed Geophysics Division of DSIR in 1951.

During my time at the Seismological Observatory in the 1960s and 70s the main building housed the Time Service clocks, by then controlled by overseas radio signals rather than by astronomical observations, and the seismological workshops. The underground chambers, still labelled with "Shell Store" and "Cartridge Store" on the doors, housed the main instruments of the Wellington seismograph station, including those of the World Wide Standard Seismograph Network, sponsored by the US Government to help monitor nuclear explosions.

During my time at the observatory we managed to keep the site, and the nearby former Meteorological Office building, despite strong offers from other Government departments, but now the offices have moved to Lower Hutt as part of the Institute of Geological and Nuclear Science, and the instruments to more suitable locations."

10. Most Distant Galaxy Seen

By pushing NASA's Hubble Space Telescope to its limits, an international team of astronomers has shattered the cosmic distance record by measuring the farthest galaxy ever seen in the universe. This surprisingly bright, infant galaxy, named GN-z11, is seen as it was 13.4 billion years in the past, just 400 million years after the big bang. GN-z11 is located in the direction of the constellation of Ursa Major.

"We've taken a major step back in time, beyond what we'd ever expected to be able to do with Hubble. We see GN-z11 at a time when the universe was only three percent of its current age," explained principal investigator Pascal Oesch of Yale University in New Haven, Connecticut. The team includes scientists from Yale University, the Space Telescope Science Institute (STScI) in Baltimore, Maryland, and the University of California in Santa Cruz, California.

Astronomers are closing in on the first galaxies that formed in the universe. The new Hubble observations take astronomers into a realm that was once thought to be only reachable with NASA's upcoming James Webb Space Telescope.

This measurement provides strong evidence that some unusual and unexpectedly bright galaxies found earlier in Hubble images are really at extraordinary distances. Previously, the team had estimated GN- z11's distance by determining its colour through imaging with Hubble and NASA's Spitzer Space Telescope. Now, for the first time for a galaxy at such an extreme distance, the team used Hubble's Wide Field Camera 3 to precisely measure the distance to GN-z11 spectroscopically by splitting the light into its component colours.

Astronomers measure large distances by determining the "redshift" of a galaxy. This phenomenon is a result of the expansion of the universe; every distant object in the universe appears to be receding from us because its light is stretched to longer, redder wavelengths as it travels through expanding space to reach our telescopes. The greater the redshift, the farther the galaxy.

"Our spectroscopic observations reveal the galaxy to be even farther away than we had originally thought, right at the distance limit of what Hubble can observe," said Gabriel Brammer of STScI, second author of the study.

Before astronomers determined the distance for GN-z11, the most distant galaxy measured spectroscopically had a redshift of 8.68 (13.2 billion years in the past). Now, the team has confirmed GN-z11 to be at a redshift of 11.1, nearly 200 million years closer to the time of the big bang. "This is an extraordinary accomplishment for Hubble. It managed to beat all the previous distance records held for years by much larger ground-based telescopes," said investigator Pieter van Dokkum of Yale University. "This new record will likely stand until the launch of the James Webb Space Telescope."

The combination of Hubble's and Spitzer's imaging reveals that GN-z11 is 25 times smaller than the Milky Way and has just one percent of our galaxy's mass in stars. However, the newborn GN-z11 is growing fast, forming stars at a rate about 20 times greater than our galaxy does today. This makes such an extremely remote galaxy bright enough for astronomers to find and perform detailed observations with both Hubble and Spitzer.

The results reveal surprising new clues about the nature of the very early universe. "It's amazing that a galaxy so massive existed only 200 million to 300 million years after the very first stars started to form. It takes really fast growth, producing stars at a huge rate, to have formed a galaxy that is a billion solar masses so soon," explained investigator Garth Illingworth of the University of California, Santa Cruz.

These findings provide a tantalizing preview of the observations that the James Webb Space Telescope will perform after it is launched into space in 2018. "Hubble and Spitzer are already reaching into Webb territory,"Oesch said. "This new discovery shows that the Webb telescope will surely find many such young galaxies reaching back to when the first galaxies were forming," added Illingworth.

This discovery also has important consequences for NASA's planned Wide-Field Infrared Survey Telescope (WFIRST), which will have the ability to find thousands of such bright, very distant galaxies.

The team's findings appeared in the March 8, 2016, edition of The Astrophysical Journal.

-- A Space Telescope Science Institute press release forwarded by Karen Pollard.

11. Radio Astronomy's 70th Anniversary

January 26, 2016 marked the 70th anniversary of the first radio astronomy interferometry done by radio astronomers in the world.

A sea cliff interferometer was used by Ruby Payne-Scott at Dover Heights, Sydney at sunrise 26 January 1946. Strong Type I bursts (1 million Jansky) were observed, arising from a large sunspot. The paper was submitted to the Proceedings of the Royal Society on 22 July 1946 and published 22 August 1947 by the CSIR (pre-CSIRO) Division of Radiophysics team of Lindsay McCready, Joe Pawsey and Ruby Payne-Scott (observations by Payne-Scott).

-- From a note by Miller Goss, (U.S.) National Radio Astronomy Observatory, Socorro, New Mexico, circulated by the Astronomical Society of Australia.

12. Head-on Collision Made Moon

The Moon was formed by a violent, head-on collision between the early Earth and a 'planetary embryo' called Theia approximately 100 million years after the Earth formed, UCLA geochemists and colleagues report.

Scientists had already known about this high-speed crash, which occurred almost 4.5 billion years ago, but many thought the Earth collided with Theia (pronounced THAY-eh) at an angle of 45 degrees or more -- a powerful side-swipe (simulated in a 2012 YouTube video [https://www.youtube.com/watch?v=Fwl_JBQtH9o]). New evidence reported January 29 in the journal Science substantially strengthens the case for a head-on assault.

The researchers analysed seven rocks brought to the Earth from the Moon by the Apollo 12, 15 and 17 missions, as well as six volcanic rocks from the Earth's mantle -- five from Hawaii and one from Arizona.

The key to reconstructing the giant impact was a chemical signature revealed in the rocks' oxygen atoms. (Oxygen makes up 90 percent of rocks¹ volume and 50 percent of their weight.) More than 99.9 percent of Earth's oxygen is O-16, so called because each atom contains eight protons and eight neutrons. But there also are small quantities of heavier oxygen isotopes: O-17, which have one extra neutron, and O-18, which have two extra neutrons. Earth, Mars and other planetary bodies in our solar system each has a unique ratio of O-17 to O-16 -- each one a distinctive 'fingerprint'.

In 2014, a team of German scientists reported in Science that the Moon also has its own unique ratio of oxygen isotopes, different from Earth's. The new research finds that is not the case.

"We don't see any difference between the Earth's and the Moon's oxygen isotopes; they're indistinguishable," said Edward Young, lead author of the new study and a UCLA professor of geochemistry and cosmochemistry.

Young's research team used state-of-the-art technology and techniques to make extraordinarily precise and careful measurements, and verified them with UCLA's new mass spectrometer.

The fact that oxygen in rocks on the Earth and our Moon share chemical signatures was very telling, Young said. Had Earth and Theia collided in a glancing side blow, the vast majority of the Moon would have been made mainly of Theia, and the Earth and Moon should have different oxygen in isotopes. A head-on collision, however, likely would have resulted in similar chemical composition of both Earth and the Moon.

"Theia was thoroughly mixed into both the Earth and the Moon, and evenly dispersed between them," Young said. "This explains why we don't see a different signature of Theia in the Moon versus the Earth."

Theia, which did not survive the collision (except that it now makes up large parts of Earth and the Moon) was growing and probably would have become a planet if the crash had not occurred, Young said. Young and some other scientists believe the planet was approximately the same size as the Earth; others believe it was smaller, perhaps more similar in size to Mars.

Another interesting question is whether the collision with Theia removed any water that the early Earth may have contained. After the collision -- perhaps tens of millions of year later -- small asteroids likely hit the Earth, including ones that may have been rich in water, Young said. Collisions of growing bodies occurred very frequently back then, he said, although Mars avoided large collisions.

A head-on collision was initially proposed in 2012 by Matija Cuk, now a research scientist with the SETI Institute, and Sarah Stewart, now a professor at UC Davis; and, separately during the same year by Robin Canup of the Southwest Research Institute.

Reference: 'Oxygen Isotopic Evidence for Vigorous Mixing During the Moon-Forming Giant Impact,' Edward D. Young et al., 2016 Jan. 29, Science [http://science.sciencemag.org/content/351/6272/493].

-- From a UCLA press release forwarded by Karen Pollard.

13. Old Stars´ Fossil Fields

Astronomers have confirmed that strong magnetic fields are frozen in place deep inside aging stars.

Stars like the Sun puff up and become red giants towards the end of their lives, so they're much larger even though the masses don't really change. The red giants ("old" Suns) of the same mass as the Sun do not show strong magnetic fields in their interior, but for stars slightly more massive, up to 60% host strong magnetic fields.

Stars create magnetic fields through convection, the swirling, Ferris- wheel-like motion of hot, ionized gas (or boiling water, for that matter). Where convection happens in a star depends on how massive the star is: low-mass stars, including the Sun, have convective outer envelopes around a non-convective core, but stars a little bulkier - up to a couple Suns´ worth - do have convective cores.

Recently, Jim Fuller (Caltech) and colleagues found that strong core magnetic fields could explain the oddly weak, on-and-off brightening behaviour of a sample of red giant stars. These stars are low- to middle-mass and have stopped fusing hydrogen in their centres, so they don´t have convective hearts. They also often have a mismatched, variable glow, with one hemisphere brightening as the other fades. What was strange about the sample the team looked at was that this group didn´t vary as much in brightness as it should have.

Now, Dennis Stello (University of Sydney and Aarhus University, Denmark), Fuller, and their team has expanded this work to 3,600 red giants, observed with the Kepler spacecraft. The astronomers found that here, too, some red giants had "muffled" variations, but just how much they were suppressed depended on how massive the star was. For stars just above the Sun´s mass and lighter, the stars looked normal. But for the heftiest of the sample - 1.6 to 2 solar masses - about half are "depressed," the team reported January 6th at the American Astronomical Society meeting in Kissimmee, Florida, and in the January 21st Nature.

This mass boundary between "normal" and "depressed" red giants is also the transition point from non-convective to convective cores. So this result is a nice confirmation that astronomers can track the strength of a star´s internal magnetic field using these brightness patterns. That prospect excites researchers, because magnetic fields play a big role in stars´ evolution and death, but astronomers don´t understand the details.

However, as noted, red giants don´t have convective cores. But they used to, before their central hydrogen-fusion furnaces shut off. So the fields muffling the variations are fossils. Magnetic fields are like strings, Fuller says, and they get twisted and tangled by the churning, convective plasma. Once this boiling motion disappears, the field essentially freezes in place. So long as there are no big, bulk motions to disrupt the field, it should just stay put.

What the team doesn´t know is whether these fossil fields will survive once the stars kick-start core helium fusion, which is the next stage in their aging process. If the fields do survive, they might be the source of the strong magnetism detected in some white dwarfs, which are the final state these red giants are approaching. The fields might also explain the "extra internal mixing" that seems to go on in some red giants and their older siblings.

Reference: Stello, Dennis et al. "A prevalence of dynamo-generated magnetic fields in the cores of intermediate-mass stars." Nature. January 21, 2016.

See more at: http://www.skyandtelescope.com/astronomy-news/old-stars-fossil-fields-2101201623/

-- From the above article by Camille M. Carlisle.

14. 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 2015 year starts at $40 for an ordinary member, which includes an electronic subscription to our journal 'Southern Stars'.

15. Previously Unknown Cluster of Nothingness Discovered

WASHINGTON - Saying the finding would further scientists´ understanding of the most remote parts of the universe, NASA astronomers announced at a press conference Thursday that they had discovered a previously unknown cluster of nothingness in deep space. "Through the use of high-resolution infrared imaging, we have identified a large grouping of total emptiness roughly 8.5 billion light-years away that had heretofore gone undetected," said NASA lead researcher Edward Hefter, adding that the newly discovered blank expanse, which is located between two immense regions of nothing, was far larger and more insignificant in scope than first thought. "We are continuing to investigate the age and origin of the emptiness, but it will be a slow process given that there is absolutely nothing in the cluster to study. However, initial data indicate that the space likely formed when a smaller void merged with a larger vacuum." Hefter added that the distant cluster of nothingness strongly resembles 481 million similar such regions discovered in recent decades.

See the original article with image at http://www.theonion.com/article/astronomers-discover-previously-unknown-cluster-no-51875

Newsletter editor:

Alan Gilmore Phone: 03 680 6817
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