Astronomy_News_20_01_2020
Astronomy_News_20_01_2020
This months research Papers 20_12_2019
RASNZ_20_01_2020
Further links and discussion can be found at the groups/links below
Astronomy in New Zealand - Facebook
https://www.facebook.com/groups/5889909863/
Astronomy in New Zealand - Groups.io
https://groups.io/g/AstronomyNZ
Astronomy in Wellington
https://www.facebook.com/groups/11451597655/
Blogger Posts
http://laintal.blogspot.com/
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Research papers
Spin dynamics of close-in planets exhibiting large TTVs
https://arxiv.org/abs/1705.04460
Simulations of Water Vapor and Clouds on Rapidly Rotating and Tidally Locked Planets
https://arxiv.org/abs/1912.11329
Transition from eyeball to snowball driven by sea-ice drift on tidally locked terrestrial planets
https://arxiv.org/abs/1912.11377
Emergence of life in an inflationary universe
https://arxiv.org/abs/1911.08092
Transfer of Life by Earth-Grazing Objects to Exoplanetary Systems
https://arxiv.org/abs/2001.02235
How planetary surfaces can shape the climate of habitable exoplanets
https://arxiv.org/abs/2001.00085
Creation and Evolution of Impact-generated Reduced Atmospheres of Early Earth
https://arxiv.org/abs/2001.00095
Detectability of Molecular Signatures on TRAPPIST-1e
https://arxiv.org/abs/2001.01338
The 3.4 µm absorption of the Titan's stratosphere
https://arxiv.org/abs/2001.02791
MCMCI a code to fully characterize an exoplanetary system
https://arxiv.org/abs/1912.12632
The Thermal Evolution Of The Early Moon
https://arxiv.org/abs/2001.07123
Long-term Periodicities in North-South Asymmetry of Solar Activity
https://arxiv.org/abs/2001.05879
3D maps of the Magellanic Clouds using Classical Cepheids
https://arxiv.org/abs/2001.05899
Fundamental limits from chaos on instability time predictions in compact planetary systems
https://arxiv.org/abs/2001.04606
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Interesting News items
Kiwi astronomers among those worried by Elon Musk's plan to launch thousands of satellites
https://www.stuff.co.nz/science/117762106/kiwi-astronomers-among-those-worried-by-elon-musks-plan-to-launch-thousands-of-satellites
Alone in a Crowded Milky Way
https://www.scientificamerican.com/article/alone-in-a-crowded-milky-way/
New Technique May Give Webb Space Telescope a Way to Quickly Identify Planets with Oxygen
http://astrobiology.com/2020/01/new-technique-may-give-webb-space-telescope-a-way-to-quickly-identify-planets-with-oxygen.html
Summer weather
https://www.stuff.co.nz/national/118856594/weather-system-blocking-warmer-temperatures-reaching-wellington
Earth-Size Planet in a Habitable Zone
https://www.jpl.nasa.gov/news/news.php?feature=7569
https://theconversation.com/an-earth-sized-planet-found-in-the-habitable-zone-of-a-nearby-star-129290
By Carlos Hernandez
Astronomers have discovered an Earth-size exoplanet orbiting a red dwarf star within its habitable zone (range of orbits around a star within which a planetary surface can support liquid water given sufficient atmospheric pressure) approximately 100 light years from the Earth in the southern constellation of Dorado, the dolphin fish.
TOI 700 (TOI is Transiting Exoplanet Survey Satellite Object of Interest) is a red dwarf star (spectral type M2V) located 101.4 light-years in the southern constellation of Dorado, the dolphin fish. TOI 700 is approximately 42% the diameter and mass and 50% the temperature of the Sun. It’s surface temperature is 3,480° Kelvin (versus the Sun’s temperature of 5,778° Kelvin) and has an estimated age of greater than 1.5 billion years (vs. the Sun’s age of 4.5 billion years). Very little flare (sudden increase in brightness of a star) activity has been noted from this star. Excessive flare activity of a star is believed to decrease the possibility of life forming over an exoplanet due to damaging radiation.
NASA’s Transiting Exoplanet Survey Satellite (TESS) discovered three exoplanets orbiting TOI 700 after watching a dip in the brightness of the star as they crossed the disk of the red dwarf star. The three exoplanets were also confirmed by NASA’s Spitzer Space Telescope. The inner planet is TOI 700b is most likely an Earth-sized rocky planet (approximately Earth’s diameter) that orbits the star in approximately 10 days at a distance of approximately 6 million miles (vs. the Earth’s distance of ~93 million miles (150 million km)). The middle planet is TOI 700c is approximately 2.6 times the Earth’s diameter and is probably a gas giant similar to Neptune. It orbits TOI 700 in a period of 16 days at an average distance of 8.6 million miles (13.8 million km). The outer planet TOI 700d orbits the red dwarf star within its habitable zone at an average distance of 15.3 million miles (24.4 million km) in a period of 37.4 days. TOI 700d is likely a Earth-size rocky planet (1.2 times Earth’s diameter) that may (but not proven) have liquid water over its surface. Astronomers are hoping that larger Earth-based instruments and the future James Webb Space Telescope (JWST) will provide additional information on these, and others, exoplanets in the future.
The first image is a painting I produced of what the surface of the outer exoplanet TOI 700d may appear as with liquid water upon it’s surface. It’s red dwarf star is partially obscured over it’s sky. The second image is another painting that I produced of the very hot and nearly boiling surface of the inner planet TOI 700b. The third image is a painting that I produced of the middle Neptune-size exoplanet TOI 700c with a small rocky satellite orbiting it. The fourth image shows the orbits of the three exoplanets (TOI 700 b, c, and d) and the red dwarf star’s habitable zone. (Image courtesy of NASA).
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Updates from Andrew B,
Wednesday 15th January 2020.
Ashford, Kent, United Kingdom.
Orion rising.
Orion the Hunter seen here in a quick image, propped the camera against the camera bag.
Notice even in this hurried shot, how the star at the top left, Betelgeuse / Alpha Orionis has faded considerably as compared to normal.
There is a general five year brightness cycle with this gigantic, dying red supergiant star, but this particular dimming is very unusual, certainly the dimmest I have ever seen Betelgeuse. I have known Orion since I was about five, never do I remember seeing Betelgeuse dim like this before.
Betelgeuse / Alpha Orionis has a mass of approximately 19.7 times greater than our Sun or about 6.6 million times that of the Earth. Our Sun by contrast has a mass of 332,946 Earths.
The diameter of Betelgeuse is about 1.329 Billion KM / 825.802 million miles or some 955 times that of our Sun or 104,100 times that of the Earth. Our Sun is much smaller at 1,391,400 KM / 864,600 miles wide or 109 times wider than the Earth.
Betelgeuse takes about 17 years to rotate on it's axis as against 25 days for our own Sun.
Camera: Canon Powershot SX 430 IS.
Taken by: Andrew R Brown.
Wednesday 15th January 2020.
Ashford, Kent, United Kingdom.
Orion rising.
Orion the Hunter seen here in a quick image, propped the camera against the camera bag.
Notice even in this hurried shot, how the star at the top left, Betelgeuse / Alpha Orionis has faded considerably as compared to normal.
There is a general five year brightness cycle with this gigantic, dying red supergiant star, but this particular dimming is very unusual, certainly the dimmest I have ever seen Betelgeuse. I have known Orion since I was about five, never do I remember seeing Betelgeuse dim like this before.
Betelgeuse / Alpha Orionis has a mass of approximately 19.7 times greater than our Sun or about 6.6 million times that of the Earth. Our Sun by contrast has a mass of 332,946 Earths.
The diameter of Betelgeuse is about 1.329 Billion KM / 825.802 million miles or some 955 times that of our Sun or 104,100 times that of the Earth. Our Sun is much smaller at 1,391,400 KM / 864,600 miles wide or 109 times wider than the Earth.
Betelgeuse takes about 17 years to rotate on it's axis as against 25 days for our own Sun.
Camera: Canon Powershot SX 430 IS.
Taken by: Andrew R Brown.
Jupiter moon Ganymede.
Imaged: Thursday 26th December 2019 / Boxing Day 2019.
A very unusual view of the giant moon Ganymede, looking pretty well straight down onto the north pole of the giant moon, by the Jovecentric (Jupiter centred) orbiting JUNO spacecraft using the JUNOCAM, shortly prior to reaching Perijove (closest approach to Jupiter in a Jovecentric orbit). Here is seen mostly the sunlit northern hemisphere.
Mostly seen here is the Perrine Regio Quadrangle and the north polar Etana Quadrangle (which appears slightly brighter due to a thin 'frost'), on the Jupiter facing side on Ganymede.
Ganymede orbits Jupiter once every 7 days, 3 hours & 43 minutes. The rotational period is the same, so Ganymede keeps the same face turned towards Jupiter as our own Moon does with Earth. The mean orbital distance is 1,070,400 KM / 664,718 miles from Jupiter.
Ganymede orbits Jupiter at an average a speed of 10.88 KPS / 6.76 MPS or 39,168 KPH / 24,323 MPH.
Ganymede is 5,269 KM / 3,273 miles in diameter & is the largest and most massive moon in the entire solar system. Ganymede is larger than the planets Mercury, Eris and Pluto, though has only about 45% of the mass of Mercury, but is approximately 12 times more massive than Pluto and 10 times more massive than Eris.
Ganymede has an average density of 1.94 grams per cubic centimetre, roughly 50% ice, 50% rock / metal. There is a fairly large iron core most likely 1,000 KM / 621 miles wide, with a silicate rich mantle and an ice crust with a postulated 800 KM / 497 mile deep subsurface salty ocean.
The average surface temperature on Ganymede is minus 163 Celsius / minus 261 Fahrenheit or 110 Kelvin. The minimum at the poles are around minus 210 Celsius / minus 364 Fahrenheit or 63 Kelvin. The ice surface is almost as hard as rock at these temperatures.
Ganymede has huge ridges and dark, cratered regions. There are cryovolcanic features, that erupted slushy ices. There is a frost cap around the north polar region.
Ganymede is the only moon in the solar system that generates its own global magnetosphere, with gravity data suggesting that Ganymede like Earth and the planet Mercury has a dual layered core, a solid iron inner core and a molten iron sulphide outer core.
Text: Andrew R Brown.
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Royal Astronomical Society of New Zealand
eNewsletter: No. 229, 20 January 2020
Affiliated Societies are welcome to reproduce any item in this email newsletter or on the RASNZ website www.rasnz.org.nz in their own newsletters provided an acknowledgement of the source is also included.
Contents
1. Betelgeuse Unusually Faint
2. Annual General Meeting Deadlines
3. Subscriptions and Reports Due
4. The Solar System in February
5. 2020 Conference and RASNZ Centenary
6. Call for Papers for 2020 RASNZ Conference
7. Star Parties in 2020
8. Variable Star News
9. Denis Sullivan
10. Australite Tektite Crater Found?
11. A Second Planet around Proxima Centauri?
12. Quasar Imaging Tests Dark Matter and the Hubble Constant
13. How to Join the RASNZ
14. Gifford-Eiby Lecture Fund
15. Quotes
1. Betelgeuse Unusually Faint
The bright star Betelgeuse has faded to a historic low. Currently Betelgeuse is in the north at dusk. It is the orange star directly below and right of the line of three stars making Orion's belt, or the bottom of the 'The Pot' in our southern hemisphere view.
On the list of brightest stars, Betelgeuse ranks 10th. But that’s only an average. The star's brightness typically varies from magnitude 0.2, roughly like Rigel, the bluish-white star above Orion's belt, to about 1.3. That's only a few tenths of magnitude brighter than Bellatrix (magnitude 1.6), the star to the left of Betelgeuse. (Bellatrix and Rigel are also variable stars, but they vary less in brightness than Betelgeuse does.)
As recently as October, Betelgeuse was around magnitude 0.5, considerably brighter than Aldebaran (0.9), the orange star below and left of Betelgeuse. But in December there was a steep drop in brightness. On December 28 it was estimated to be magnitude of 1.5, nearly equal in brightness to Bellatrix. In just two months it's fallen from 10th place to 21st, according to astronomer James Kaler's 26 Brightest Stars list, a remarkable decline — and a historic low.
Betelgeuse is a pulsating red supergiant. It physically expands and contracts as its atmosphere alternately traps and releases heat radiating from its core. When the star is smallest and hottest, it would extend to the orbit of Mars if put in place of the Sun. When largest and coolest it would balloon to span Jupiter's orbit. Although Betelgeuse is 20 times more massive than the Sun, its expanding shell has only 1/10,000 the density of air — it might be better described as a red-hot vacuum.
Betelgeuse is a semi-regular variable star with multiple periods of variation. The primary pulsations repeat every ~425 days, but the star also shows additional changes in brightness with periods of 100-180 days and 5.9 years. Dark patches that resemble monstrous sunspots as well as bright blobs of upwelling gas are behind some of these fluctuations. Betelgeuse is clearly in upheaval and will continue to surprise us before it eventually runs out of fuel, collapses, and explodes as a Type II supernova.
While the supergiant's current behaviour is out of the ordinary, it doesn't necessarily mean an eruption is imminent. Astronomers predict a star-shredding blast sometime in the next 100,000 years or so.
Astronomers Edward Guinan and Richard Wasatonic, both at Villanova University, along with amateur Thomas Calderwood, have been monitoring the star for more than 25 years. They reported a decline to magnitude 1.29 on December 20th using precise V-band photometry, making this the faintest minimum since the star was first monitored electronically in the early 20th century.
In Astronomical Telegram #13365 Guinan writes: "The current faintness of Betelgeuse appears to arise from the coincidence of the star being near the minimum light of the ~5.9-yr light-cycle as well as near the deeper than usual minimum of the ~425-d period." In effect, the star's overlapping cycles have created a sort of superminimum. Guinan encourages observers to closely monitor the star during this unusually cool and faint state.
Anyone can follow Betelgeuse's brightness changes. Use Bellatrix (magnitude 1.6) and Aldebaran (0.9) to determine its brightness to an accuracy of one-tenth of a magnitude. For instance, if Betelgeuse appears midway in brightness between Bellatrix and Aldebaran its magnitude would be about 1.3. If a little fainter or brighter one way or the other add or subtract additional tenths of a magnitude.
When making a magnitude estimate look quickly from star to star. If you stare too long, your brain will "inflate" a star's brightness. Near-sighted observers have an additional tool at their disposal. Just take off your glasses! The stars will expand into disks, making it easier to detect subtle brightness differences.
Then write that number down and return every few nights or maybe every week and make another estimate. Over time you’ll see it change right before your eyes. Betelgeuse is expected to continue fading into January and then re-brighten, but you never know what surprises may still be in store. Stars do as they please and that's half the fun.
[On January 19th Betelgeuse was about the same brightness as Bellatrix, so about magnitude 1.6. -- Ed.]
-- Abridged from Bob King's article of December 31 at https://www.skyandtelescope.com/observing/fainting-betelgeuse/
What’s Up With Betelgeuse?
For speculations on Betelgeuse becoming a supernova see, among others:
https://globalnews.ca/news/6414358/betelgeuse-dying-supernova/
https://www.economist.com/science-and-technology/2020/01/11/might-there-soon-be-a-supernova-near-earth
2. Annual General Meeting Deadlines
Nominations for RASNZ Council positions.
The executive positions are: President, Vice President, Executive Secretary, and Treasurer. The immediate Past President is an ex-officio position.
Five Councillors are elected by members. Two Councillors are appointed by the Affiliated Societies Committee. One Councillor is elected by the Fellows.
All nominations must be sent to the Executive Secretary (see below) by 8th February 2020. A nomination form was included in the recent Keeping in Touch #35, 17th December.
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Notices of motion for Annual General Meeting must be submitted to the Executive Secretary by Saturday, 28th March.
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Nominations for RASNZ awards and prizes -
• MURRAY GEDDES MEMORIAL PRIZE - Nominations must be made by March 8th. See By-Law G5.
• EARTH & SKY BRIGHT STAR AWARD - for contributions in NZ in promoting astronomy to the public, or in astronomical education, or in promoting dark skies. Nominations by 8th February.
• FELLOWS NOMINATION - nominations by February 8th. See Rules 14-23.
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For a link to the RASNZ rules see - https://www.rasnz.org.nz/images/articleFiles/Council/Rules2019.pdf
The Executive Secretary's email address is
John Drummond
Postal address: John Drummond, PO Box 113, Patutahi 4045.
3. Subscriptions and Reports Due
2020 RASNZ subscriptions are due on the 1st January. See - https://www.rasnz.org.nz/rasnz/payments-and-donations
Section and Group reports are due with the Executive Secretary by 9th March. For more details see By-Laws F1 - F16.
4. The Solar System in February
Dates and times shown are NZDT (UT + 13 hours). Rise and Set times are for Wellington. They will vary by a few minutes elsewhere in NZ. Data is adapted from that shown by GUIDE 9.1
THE SUN and PLANETS in February, Rise & Set, Magnitude & Constellation.
February 1 NZDT February 29 NZDT
Mag Cons Rise Set Mag Cons Rise Set
SUN -26.7 Cap 6.23am 8.44pm -26.7 Aqr 6.58am 8.07pm
Merc -1.0 Cap 7.35am 9.28pm -1.0 Aqr 6.38am 7.33pm
Venus -4.0 Aqr 9.50am 10.28pm -4.1 Psc 10.47am 9.44pm
Mars 1.6 Oph 2.17am 5.24pm 1.4 Sgr 1.48am 5.00pm
Jup -1.8 Sgr 4.03am 7.05pm -1.9 Sgr 2.40am 5.37pm
Sat 0.5 Sgr 4.58am 7.46pm 0.6 Sgr 3.23am 6.06pm
Uran 5.7 Ari 1.18pm 12.02am 5.8 Ari 11.32am 10.13pm
Nep 7.9 Aqr 9.26am 10.17pm 7.9 Aqr 7.41am 8.29pm
Pluto 14.6 Sgr 4.47am 7.44pm 14.6 Sgr 3.01am 5.57pm
February 1 NZDT February 29 NZDT
Twilights morning evening morning evening
Civil: start 5.55am, end 9.13pm start 6.32am, end 8.34pm
Nautical: start 5.17am, end 9.51pm start 5.59am, end 9.07pm
Astro: start 4.35am, end 10.33pm start 5.23am, end 9.42pm
February PHASES OF THE MOON, times NZDT & UT
First quarter: Feb 2 at 2.42pm (01:42 UT)
Full Moon: Feb 9 at 8.33pm (07:33 UT)
Last quarter Feb 16 at 11.17am (Feb 15, 22:17 UT)
New Moon: Feb 24 at 4.32am (Feb 23, 15:32 UT)
PLANETS in FEBRUARY
MERCURY is in the early evening sky most of February. At first it sets 40 to 45 minutes after the Sun, so will be a difficult object in the evening twilight. The planet is at greatest elongation, 18° east of the Sun on the 10th. It is stationary on the 16th and at inferior conjunction, between the Earth and Sun, on the 26th. Following conjunction, Mercury becomes a morning object but rises only a few minutes before the Sun by the 29th.
VENUS is an evening object setting about 90 minutes after the Sun. It is in Pisces most of the month. Venus will be fairly low and a little to the north of west shortly after sunset. On the 27th the crescent moon will be 7° to the upper left of Venus.
MARS, JUPITER and SATURN are all morning objects, forming a steeply inclined line to the east with Mars highest and Saturn lowest. They get closer to one another during the month. By the end of February the separation of Mars from Jupiter will be 11° with Saturn 8.5° below Jupiter. The three will be a little to the south of east. The crescent moon passes the three planets on the mornings of February 19, 20 and 21 respectively. Occultations of Mars and Jupiter by the moon are not visible from NZ.
PLUTO is between Jupiter and Saturn, closer to the latter.
URANUS is an evening object setting a little after 11pm at the end of February. By then NEPTUNE sets only 20 minutes after the Sun.
POSSIBLE BINOCULAR ASTEROIDS in FEBRUARY
February 1 NZDT February 29 NZDT
Mag Cons transit Mag Cons transit
(1) Ceres 9.1 Cap 12.49pm 9.3 Cap 11.46am
(4) Vesta 8.0 Ari 7.36pm 8.3 Tau 6.13pm
(5) Astraea 9.3 Cnc..12.35pm 10.0 Gem 10.32pm
CERES is a low morning object just over 7° to the lower right of Saturn on the 1st. Their distance apart doubles by the 29th as the faster moving asteroid draws away from the planet.
VESTA is an evening object. It moves into Taurus at the end of February when it will be about 10° from the Pleiades.
ASTRAEA fades from 9.3 to 10 during the month. It is likely to be lost to binocular view by mid-February.
-- Brian Loader
5. 2020 Conference and RASNZ Centenary
It is a pleasure to announce that the next conference of the Royal Astronomical Society of New Zealand (RASNZ) will be held at the Wharewaka Function Centre on Wellington waterfront over the weekend of 8 - 10 May 2020. The Wellington Astronomical Society is hosting the Conference.
This year is the 100th anniversary of the formation of the Society and to honour this special occasion we will be welcoming four invited speakers. They will be Dr Dom Pesce (Black Hole Initiative, Harvard University), Professor Anna Scaife and Dr Rene Breton (Manchester University/Jodrell Bank) and Dr Chris Lintott (Oxford University). This year the Fellows´ Lecture will be given by long standing Society member and past president John Drummond. Titles and abstracts for these talks will be released when they are available.
As the programme will commence at the earlier than usual time at 1pm on Friday we encourage as many as possible to make their travel arrangements to arrive in the city during the morning.
The conference will be preceded by a Dark Sky Workshop on the morning of
Thursday 7 May. The workshop will consist of short talks on relevant key local and international dark sky updates and discussion/demonstration on topics such as sky quality measurements and dark sky friendly lighting.
The RASNZ website now has available the conference brochure, on-line registration (and downloadable form) and paper submission (via the registration page). See it all here: http://www.rasnz.org.nz/groups-news-events/rasnz-conference.
Please consider participating in this Conference as RASNZ celebrates its centenary - we look forward to seeing you there.
-- Glen Rowe, Chair, Standing Conference Committee.
6. Call for Papers for 2020 RASNZ Conference
The RASNZ Standing Conference Committee (SCC) invites and encourages anyone interested in New Zealand astronomy to submit oral or poster papers, with titles and abstracts due by 1 April 2020 or until such time as the SCC deems the conference programme to be full. The link to the paper submission form can be found on the RASNZ Conference website http://rasnz.org.nz/groups-news-events/rasnz-conference. Please note that you must be registered for the conference to give an oral presentation, and for your convenience a link has been provided if you wish to do this when you submit a paper.
We look forward to receiving your submissions and seeing you at the conference. Please feel free to forward this message to anyone who may find it of interest.
For further information on the RASNZ Conference, registration details and associated events please visit the conference website at http://rasnz.org.nz/groups-news-events/rasnz-conference.
-- Warwick Kissling, RASNZ Standing Conference Committee
7. Star Parties in 2020
The following star parties are planned for 2020:
Stardate North Island: Friday February 21st to Sunday 23rd at Stonehenge, Carterton. Check Phoenix website - http://www.astronomynz.org/
Stardate South Island: Friday February 21st to Sunday 23rd, at Staveley, South Island. Keep an eye on https://cas.org.nz/
Stargazers Getaway 2020 Camp Iona, Friday September 18th to Sunday 20th. This is new Moon, so we are targeting this weekend for dark skies! See
https://www.facebook.com/events/943327669369996/
NACAA: The 29th NACAA conference will be held in the NSW (Australia) regional city of Parkes (where the world-famous Parkes Radio Telescope is) over the 2020 Easter weekend, Friday April 10th – Monday 13th. For more details see http://nacaa.org.au/2020/about
-- Mostly from 'Keeping in Touch' #34, 27th Sept 2019.
8. Variable Star News
VSS Symposium 6
The next Variable Stars South Symposium is to be held in association with the National Australian Convention of Australian Astronomers (NACAA), Easter 2020 at Parkes (site of the famous large steerable dish Radio Telescope). VSSS6 will be held on Friday, April 10th, 2020. There is usually an informal get together on the evening prior. An outline of the format is given in the Oct. 2019 newsletter (available under Community on the VSS website.) The next VSS newsletter is due for publication towards the end of January and should contain more information on the event.
The website for the NACAA event is https://nacaa.org.au/2020/about. The NACAA conference is over three days, Saturday to Monday, and information on the programme is available there.
Irregular Variations
A recent AAVSO Alert Notice, No 691, called for urgent monitoring of ASASSN-V J060000.76-310027.83 in the southern constellation of Columba (The Dove). This star is normally visual magnitude 13.6 but has undergone a small but unexpected fade. The discovery was made with the All Sky Automated Survey (ASAS-SN) operated by Ohio State University. The star is a nearby (d~155 pc) K5 dwarf star. At the time of the announcement (8 Jan 2020) the cause of the fading could not be identified; it has been suggested it may be due to a dust cloud around an unknown companion. Urgent photometry was called for; refer to the alert notice for guidelines.
For those interested in notices of transient phenomena, advice of alerts is being posted by Mark Blackford on the VSS Google Discussion Group.
The bright star Betelgeuse in Orion (alpha Orionis) hit the news headlines in December with the announcement that it was experiencing an unusually deep fade described as a possible prelude to a supernova in our immediate star neighbourhood. The media has moved on but not surprisingly the star is receiving close attention from a large number of observers. The star is normally at V mag 0.5 and a decrease is normally 0.3 mag. to something above magnitude 1.0 at most, a very small decrease (magnitudes quoted are V-filter). At the time of writing (16th Jan) the brightness is about mag. 1.5 and there is no indication that the star has reached its minimum brightness. The steep decline is very different to the normal shallow oscillation. It will be interesting to see at what point the decline flattens out. Observing is best done by experienced observers as reddish stars are difficult to assess visually and because of the brightness comparison stars are limited.
-- Alan Baldwin
9. Denis Sullivan
RASNZ Fellow Denis Sullivan died at his home on Christmas day after a brief illness.
The following is from a tribute by John Lekner of Victoria University of Wellington, forwarded by Pauline Harris.
Denis joined the Physics Department in 1968, so we have lost our longest-serving physicist. He was born and educated in Sydney, first as an engineer (it showed: he had a lifelong appreciation, even love, of good tools and clever devices, and was very good at implementing the electronics of data collection). He changed to physics and went to ANU for graduate study, where he met Whetu Tirikatene. They married and came to Wellington because of Whetu's political connections, and Denis got a job at the Institute of Nuclear Sciences, later to form a part of the current GNS, and then as lecturer at Vic. His graduate training was in nuclear physics, and he first worked on electron-positron annihilation, but then joined David Beaglehole and Joe Trodahl in what was for all of them a new venture: astronomy. Both David and Joe eventually went back to their condensed matter research, while Denis prospered in his new-found field, building up astronomy courses and continuing observational astronomy. His research interests included pulsating white dwarfs, microlensing, and most recently extra-terrestrial planets. This year's Nobel Prize was awarded for the detection of the earliest known extra-terrestrial planets. Currently there are about four thousand known, but when Denis joined the field there was only a handful. Denis happened to be at the Mauna Kea observatory in Hawaii when the position of one of the possible early ones was circulated among astronomers. Denis and Tiri (at the time his graduate student) were able to independently confirm, by a different observational method, the existence of that planet, about number 3 or 4 at the time. So Denis was in at the beginning of what is now almost an astronomical industry.
Denis was an excellent teacher: I have some of his astronomical notes, which are so meticulous and clear they are a pleasure to read. He was a very good speaker also, with a lovely sense of humour. His tolerance of bureaucracy was notably low; likewise of any kind of pretence or dishonesty. I came to value his opinion on political and historical matters, as well as on physics. He had practical wisdom, balance, generosity. It is a privilege to have been his colleague.
10. Australite Tektite Crater Found?
Tektites are small (generally less than 5 cm across) glassy objects found in several parts of the world. They have aerodynamic shapes, teardrop and similar, showing that they have been heated by passing through the atmosphere. They are the 'splash' from big meteorite impacts. Molten rock has been ejected into space then fallen back to Earth, being heated a second time coming through the air. They are found in several parts of the world. Some have been identified with major impact craters.
The youngest and largest 'strewn field' of tektites extends from southern China across southeast Asia and Australia to the edge of Antarctica. Some have been found as far west as Africa. They are variously known as Australites, Indochinites, Philippinites and other names and are around 790,000 years old. Their source crater hasn't previously been identified.
Now, researchers think they've found the crater responsible buried under the Bolaven Plateau, a sandstone and mudstone plateau in southeastern Laos that's covered in hardened lava up to 300 metres thick.
The Bolaven crater “is likely the largest crater (on Earth) formed within the past million years,” says study lead Kerry Sieh (Earth Observatory Singapore). The recent crater reported under the Greenland ice sheet is larger, he adds, but its age is still unclear.
In a study appearing December 30th in the Proceedings of the U.S. National Academy of Sciences, Sieh and colleagues laid out four individual lines of evidence pointing to the existence of a crater under the Bolaven Plauteau as the source of the Australasian strewn field.
The researchers first tested the tektite fragments themselves, to see if they contained basalts, which would indicate their origin on the volcanic plateau. Then they tested the proposed impact site, dating the basalts there and mapping the region's density to look for evidence of a buried impact crater. Indeed, mapping of gravitational anomalies in the area showed hints of a 17 km by 13 km crater buried beneath the volcanic plain in southeastern Laos.
"Now that we know the site of the impact, we can begin to investigate how the surrounding areas were affected by the impact,” says Sieh. “For example, how thick and coarse was the ejecta blanket, 10, 50 300 km away?” From this, he says, we can understand the effect of the shock wave that blasted outward after the impact.
The object that made the crater was likely a 2-km wide asteroid that came in at a shallow angle, gouging out the 17-km wide crater and showering the surrounding region with debris. While the impactor was 30 times smaller than the one that caused the Chicxulub extinction event 66 million years ago, it was 100 times bigger than the more recent bolide that exploded over Chelyabinsk, Russia, in 2013.
Intriguingly, the sedimentary layer where geologists find Australasian tektites, which is 790,000 years old, overlaps with the timeframe of the sediments in which the 770,000-year-old Peking Man (Homo erectus) was found. Maybe early hominids witnessed this catastrophic event!
For maps and images see David Dickinson's article at https://www.skyandtelescope.com/astronomy-news/new-location-proposed-for-australasian-strewn-field-source-crater/
from which most of the above was taken.
11. A Second Planet around Proxima Centauri?
Less than four years after the discovery of a planet orbiting our closest neighbouring star, Proxima Centauri, scientists think they’ve discovered a second world in the same system.
The planet, a super-Earth called Proxima Centauri c (Proxima c for short), has at least six times more mass than Earth and orbits its star every 5.2 years. The discovery appears January 15th in the open-access journal Science Advances.
The first planet to be discovered in this system, Proxima b, initially raised astronomers’ hopes: The Earth-size planet orbits Proxima Centauri every 11.2 days, putting it in the so-called habitable zone, where liquid water may exist on a rocky surface. However, further study has showed that the magnetically active star likely robbed the planet of its atmosphere long ago.
To find the new super-Earth, scientists used the HARPS spectrograph at the La Silla Observatory and the UVES spectrograph on the Very Large Telescope, both in Chile. Mario Damasso (Astrophysical Observatory of Torino, Italy) and colleagues analyzed data collected between 2000 and 2017, looking for the signature “wobble” in Proxima’s Centauri’s light spectrum that would indicate the presence of a planet, the same technique that enabled scientists to confirm the Proxima b’s presence in 2016.
“Stars like Proxima Centauri are rather restless and continuously present eruptions and spots on their surface, which make the detection of a planetary-induced oscillation very complicated,” says coauthor Fabio Del Sordo (University of Crete and Foundation for Research and Technology-Hellas in Heraklion, Greece). Because the observations span almost two decades, the scientists have confidently ruled out those sources of noise, but they caution that follow-up observations are needed to confirm that the signal comes from a planet.
Proxima c is about 1.5 astronomical units (a.u.) away from its star — just a little farther out than Earth is from the Sun, but about 30 times farther out than Proxima b. Because of this large distance, even if the planet were rocky, it would be too cold to host life as we know it.
The planet’s existence challenges theories explaining the formation of super-Earths. Scientists think that super-Earths like Proxima c should form near a snowline — the region where gaseous compounds such as water, carbon monoxide, or ammonia solidify into ices. These regions are sweet-spots for super-Earth formation, yet this planet orbits much farther out than the snowlines in its system.
It’s also unlikely that the planet would have formed close to its star only to be kicked farther out, because planet searches indicate that there are no massive planets on closer orbits that could have done the kicking.
Future observations with observatories ranging from the space-based Gaia mission to the submillimeter-wavelength ALMA dishes will help confirm the planet’s existence and explain the planet’s formation.
See Julie Freydlin's original article at https://www.skyandtelescope.com/astronomy-news/proxima-centauri-c-second-planet-nearest-star-system/
12. Quasar Imaging Tests Dark Matter and the Hubble Constant
The Hubble Space Telescope, which will celebrate its 30th birthday this April, has imaged cosmic mirages that yield two remarkable cosmological results. One constrains the nature of dark matter, the other further deepens the controversy about how fast the universe is currently expanding. Two teams of astronomers presented the two results at a meeting of the American Astronomical Society in Honolulu.
The two Hubble breakthroughs stem from meticulous observations of gravitational lenses – a kind of cosmic mirage created when gravity bends light. In these cases, the background light comes from a quasar, the luminous core of a galaxy containing a supermassive black hole. General relativity explains how a massive foreground galaxy — if it’s aligned just right — can split the light from such a quasar into four individual images. Moreover, gravitational lensing may enhance the apparent brightness of these images. Astronomers can then study the mirage, sometimes called an Einstein’s Cross, to measure fundamental properties of the universe.
In the first study, led by Anna Nierenberg (NASA/Jet Propulsion Laboratory), Hubble studied eight quasars, whose light has travelled some 10 billion years; each one is quadruply lensed by a foreground galaxy about five times closer.
Based on the lens geometry, astronomers can calculate the expected relative brightness of the four images. But such calculations assume that mass is smoothly distributed throughout the lens halo. In reality, however, the light-bending effects of dark matter clumps in the lens galaxy’s halo will change these expected values.
The number and dimensions of these dark matter clumps strongly influence the relative brightnesses of the quasar images. The Hubble data indicate that the dark matter clumps tend to be relatively small, just one-hundred-thousandth the total mass of our Milky Way galaxy.
The result rules out the existence of warm dark matter, the idea that dark matter consists of “warm” (fast-moving) particles. Some cosmologists have suggested that dark matter might be warm because dark matter searches for cold (or more slowly moving) particles have turned up empty. But fast-moving particles have a hard time clumping together in small, low-mass concentrations.
According to Nierenberg, the Hubble observations constitute the strongest evidence yet for cold, low-velocity dark matter. The results were published in the December 24th Monthly Notices of the Royal Astronomical Society and also appearon the arXiv preprint server.
https://arxiv.org/abs/1908.06983
In the second study, astronomers on the team known as H0 Lenses in COSMOGRAIL’s Wellspring (H0LiCOW) focused on the “flickering” of quadruply lensed quasars.
True luminosity variations of the quasar — most likely caused by the varying activity of the central black hole — show up at different times in the four images. That’s because to produce each image, the quasar’s light follows a different path to the observer, and each path is a slightly different length. The time delays for the longer paths, combined with a map of the way mass is distributed in the foreground galaxy, yield a unique three-dimensional picture of the gravitational lens. As a result, astronomers can measure precise distances to both the quasar and the lensing galaxy. Moreover, these values are completely independent of other distance measures.
Distances are crucial for measuring the current expansion rate of the universe. Astronomers typically estimate a galaxy’s distance by its redshift, which measures how the wavelength of light stretches as it traverses expanding space. But to understand how fast space is expanding, astronomers need a distance measure that’s independent of redshift — that’s what the lensed quasars provide.
The H0LiCOW team uses the new Hubble data to obtain the most precise value of the current expansion rate yet obtained from gravitational lens studies: 73 km per second per megaparsec, with an uncertainty of 2.4 percent. (A megaparsec is 3.2 million light years.)
This value stands firmly on one side of an ongoing debate on how fast the universe is currently expanding. Estimates based on objects in the relatively nearby universe show the current expansion rate, termed the Hubble Constant, to be 74 km/s/Mpc. However, the dark energy-cold dark matter theory that successfully models the composition and evolution of the universe, combined with precise measurements of the cosmic microwave background emitted shortly after the Big Bang, puts the Hubble Constant at 67 km/s/Mpc.
The H0LiCOW collaboration analysed six multiply-imaged quasar systems, measuring the current expansion rate of the universe to be between 71.5 and 75 km/s/Mpc. This value is inconsistent with estimates obtained from modelling of the cosmic microwave background.
Folding in the results from the gravitational lensing study, the tension is so strong, says team member Geoff Chih-Fan Chen (University of California, Davis), that the term “crisis” is fully justified.
The H0LiCOW team, led by Sherry Suyu (Max Planck Institute for Astrophysics, Germany), will publish these latest results in the Monthly Notices of the Royal Astronomical Society. A preprint is available on the arXiv server https://arxiv.org/abs/1907.04869
-- Govert Schilling's article with images and diagrams at https://www.skyandtelescope.com/astronomy-news/hubble-sheds-light-on-dark-matter-and-cosmic-expansion/
13. 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 treasurer@rasnz.co.nz or
by completing the online application form found at
http://rasnz.org.nz/rasnz/membership-application
Basic membership for the 2019 year starts at $40 for an ordinary
member, which includes an electronic subscription to our journal
'Southern Stars'.
14. Gifford-Eiby Lecture Fund
The RASNZ administers the Gifford-Eiby Memorial Lectureship Fund to
assist Affiliated Societies with travel costs of getting a lecturer
or instructor to their meetings. Details are in RASNZ By-Laws Section
H and at http://rasnz.org.nz/rasnz/ge-fund
The application form is at
http://rasnz.org.nz/Downloadable/RASNZ/GE_Application2019.pdf
15. Quotes
"This morning around 13 hours a huge comet appeared in the sky, and fell toward Earth making the whole sky shine with fire, followed by a great noise as of thunder that was felt throughout the whole province, and the fire and splendour were similarly seen throughout the entire territory." -- A note by a parish priest at a small town in what is now the Province of Brescia, Northern Italy, describing a daylight fireball on 24 January 1680. Found in archives a few months ago. See http://neo.ssa.esa.int/ .
"Physics is the law. Everything else is a recommendation." -- Elon Musk quoted in 'NZ Listener' December 14, 2019, p.6.
"We are all ignorant. We are just ignorant about different things." -- Will Rogers quoted in Michael Collins's book "Carrying the Fire".
Alan Gilmore Phone: 03 680 6817
P.O. Box 57 alan.gilmore@canterbury.ac.nz
Lake Tekapo 7945
New Zealand
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Further links and discussion can be found at the groups/links below
Astronomy in New Zealand - Groups.io
https://groups.io/g/AstronomyNZ
Astronomy in New Zealand - Facebook
https://www.facebook.com/groups/5889909863/
Astronomy in Wellington
https://www.facebook.com/groups/11451597655/
Blogger Posts
http://laintal.blogspot.com/
Twitter
https://twitter.com/Laintal
Groups.io
Astronomy in New Zealand
https://groups.io/g/AstronomyNZ
AstronomyNZ@groups.io
Wellington Astronomers
https://groups.io/g/WellingtonAstronomers
WellingtonAstronomers@groups.io
AucklandAstronomers
https://groups.io/g/AucklandAstronomers
AucklandAstronomers@groups.io
North Island Astronomers
https://groups.io/g/NorthIslandAstronomers
NorthIslandAstronomers@groups.io
South Island Astronomers
https://groups.io/g/SouthIslandAstronomers
SouthIslandAstronomers@groups.io
NZAstrochat
https://groups.io/g/NZAstrochat
NZAstrochat@groups.io
NZ Photographers And Observers
https://groups.io/g/NZPhotographers
NZPhotographers@groups.io
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This months research Papers 20_12_2019
RASNZ_20_01_2020
Further links and discussion can be found at the groups/links below
Astronomy in New Zealand - Facebook
https://www.facebook.com/groups/5889909863/
Astronomy in New Zealand - Groups.io
https://groups.io/g/AstronomyNZ
Astronomy in Wellington
https://www.facebook.com/groups/11451597655/
Blogger Posts
http://laintal.blogspot.com/
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Research papers
Spin dynamics of close-in planets exhibiting large TTVs
https://arxiv.org/abs/1705.04460
Simulations of Water Vapor and Clouds on Rapidly Rotating and Tidally Locked Planets
https://arxiv.org/abs/1912.11329
Transition from eyeball to snowball driven by sea-ice drift on tidally locked terrestrial planets
https://arxiv.org/abs/1912.11377
Emergence of life in an inflationary universe
https://arxiv.org/abs/1911.08092
Transfer of Life by Earth-Grazing Objects to Exoplanetary Systems
https://arxiv.org/abs/2001.02235
How planetary surfaces can shape the climate of habitable exoplanets
https://arxiv.org/abs/2001.00085
Creation and Evolution of Impact-generated Reduced Atmospheres of Early Earth
https://arxiv.org/abs/2001.00095
Detectability of Molecular Signatures on TRAPPIST-1e
https://arxiv.org/abs/2001.01338
The 3.4 µm absorption of the Titan's stratosphere
https://arxiv.org/abs/2001.02791
MCMCI a code to fully characterize an exoplanetary system
https://arxiv.org/abs/1912.12632
The Thermal Evolution Of The Early Moon
https://arxiv.org/abs/2001.07123
Long-term Periodicities in North-South Asymmetry of Solar Activity
https://arxiv.org/abs/2001.05879
3D maps of the Magellanic Clouds using Classical Cepheids
https://arxiv.org/abs/2001.05899
Fundamental limits from chaos on instability time predictions in compact planetary systems
https://arxiv.org/abs/2001.04606
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Interesting News items
Kiwi astronomers among those worried by Elon Musk's plan to launch thousands of satellites
https://www.stuff.co.nz/science/117762106/kiwi-astronomers-among-those-worried-by-elon-musks-plan-to-launch-thousands-of-satellites
Alone in a Crowded Milky Way
https://www.scientificamerican.com/article/alone-in-a-crowded-milky-way/
New Technique May Give Webb Space Telescope a Way to Quickly Identify Planets with Oxygen
http://astrobiology.com/2020/01/new-technique-may-give-webb-space-telescope-a-way-to-quickly-identify-planets-with-oxygen.html
Summer weather
https://www.stuff.co.nz/national/118856594/weather-system-blocking-warmer-temperatures-reaching-wellington
Earth-Size Planet in a Habitable Zone
https://www.jpl.nasa.gov/news/news.php?feature=7569
https://theconversation.com/an-earth-sized-planet-found-in-the-habitable-zone-of-a-nearby-star-129290
By Carlos Hernandez
Astronomers have discovered an Earth-size exoplanet orbiting a red dwarf star within its habitable zone (range of orbits around a star within which a planetary surface can support liquid water given sufficient atmospheric pressure) approximately 100 light years from the Earth in the southern constellation of Dorado, the dolphin fish.
TOI 700 (TOI is Transiting Exoplanet Survey Satellite Object of Interest) is a red dwarf star (spectral type M2V) located 101.4 light-years in the southern constellation of Dorado, the dolphin fish. TOI 700 is approximately 42% the diameter and mass and 50% the temperature of the Sun. It’s surface temperature is 3,480° Kelvin (versus the Sun’s temperature of 5,778° Kelvin) and has an estimated age of greater than 1.5 billion years (vs. the Sun’s age of 4.5 billion years). Very little flare (sudden increase in brightness of a star) activity has been noted from this star. Excessive flare activity of a star is believed to decrease the possibility of life forming over an exoplanet due to damaging radiation.
NASA’s Transiting Exoplanet Survey Satellite (TESS) discovered three exoplanets orbiting TOI 700 after watching a dip in the brightness of the star as they crossed the disk of the red dwarf star. The three exoplanets were also confirmed by NASA’s Spitzer Space Telescope. The inner planet is TOI 700b is most likely an Earth-sized rocky planet (approximately Earth’s diameter) that orbits the star in approximately 10 days at a distance of approximately 6 million miles (vs. the Earth’s distance of ~93 million miles (150 million km)). The middle planet is TOI 700c is approximately 2.6 times the Earth’s diameter and is probably a gas giant similar to Neptune. It orbits TOI 700 in a period of 16 days at an average distance of 8.6 million miles (13.8 million km). The outer planet TOI 700d orbits the red dwarf star within its habitable zone at an average distance of 15.3 million miles (24.4 million km) in a period of 37.4 days. TOI 700d is likely a Earth-size rocky planet (1.2 times Earth’s diameter) that may (but not proven) have liquid water over its surface. Astronomers are hoping that larger Earth-based instruments and the future James Webb Space Telescope (JWST) will provide additional information on these, and others, exoplanets in the future.
The first image is a painting I produced of what the surface of the outer exoplanet TOI 700d may appear as with liquid water upon it’s surface. It’s red dwarf star is partially obscured over it’s sky. The second image is another painting that I produced of the very hot and nearly boiling surface of the inner planet TOI 700b. The third image is a painting that I produced of the middle Neptune-size exoplanet TOI 700c with a small rocky satellite orbiting it. The fourth image shows the orbits of the three exoplanets (TOI 700 b, c, and d) and the red dwarf star’s habitable zone. (Image courtesy of NASA).
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Updates from Andrew B,
Wednesday 15th January 2020.
Ashford, Kent, United Kingdom.
Orion rising.
Orion the Hunter seen here in a quick image, propped the camera against the camera bag.
Notice even in this hurried shot, how the star at the top left, Betelgeuse / Alpha Orionis has faded considerably as compared to normal.
There is a general five year brightness cycle with this gigantic, dying red supergiant star, but this particular dimming is very unusual, certainly the dimmest I have ever seen Betelgeuse. I have known Orion since I was about five, never do I remember seeing Betelgeuse dim like this before.
Betelgeuse / Alpha Orionis has a mass of approximately 19.7 times greater than our Sun or about 6.6 million times that of the Earth. Our Sun by contrast has a mass of 332,946 Earths.
The diameter of Betelgeuse is about 1.329 Billion KM / 825.802 million miles or some 955 times that of our Sun or 104,100 times that of the Earth. Our Sun is much smaller at 1,391,400 KM / 864,600 miles wide or 109 times wider than the Earth.
Betelgeuse takes about 17 years to rotate on it's axis as against 25 days for our own Sun.
Camera: Canon Powershot SX 430 IS.
Taken by: Andrew R Brown.
Wednesday 15th January 2020.
Ashford, Kent, United Kingdom.
Orion rising.
Orion the Hunter seen here in a quick image, propped the camera against the camera bag.
Notice even in this hurried shot, how the star at the top left, Betelgeuse / Alpha Orionis has faded considerably as compared to normal.
There is a general five year brightness cycle with this gigantic, dying red supergiant star, but this particular dimming is very unusual, certainly the dimmest I have ever seen Betelgeuse. I have known Orion since I was about five, never do I remember seeing Betelgeuse dim like this before.
Betelgeuse / Alpha Orionis has a mass of approximately 19.7 times greater than our Sun or about 6.6 million times that of the Earth. Our Sun by contrast has a mass of 332,946 Earths.
The diameter of Betelgeuse is about 1.329 Billion KM / 825.802 million miles or some 955 times that of our Sun or 104,100 times that of the Earth. Our Sun is much smaller at 1,391,400 KM / 864,600 miles wide or 109 times wider than the Earth.
Betelgeuse takes about 17 years to rotate on it's axis as against 25 days for our own Sun.
Camera: Canon Powershot SX 430 IS.
Taken by: Andrew R Brown.
Jupiter moon Ganymede.
Imaged: Thursday 26th December 2019 / Boxing Day 2019.
A very unusual view of the giant moon Ganymede, looking pretty well straight down onto the north pole of the giant moon, by the Jovecentric (Jupiter centred) orbiting JUNO spacecraft using the JUNOCAM, shortly prior to reaching Perijove (closest approach to Jupiter in a Jovecentric orbit). Here is seen mostly the sunlit northern hemisphere.
Mostly seen here is the Perrine Regio Quadrangle and the north polar Etana Quadrangle (which appears slightly brighter due to a thin 'frost'), on the Jupiter facing side on Ganymede.
Ganymede orbits Jupiter once every 7 days, 3 hours & 43 minutes. The rotational period is the same, so Ganymede keeps the same face turned towards Jupiter as our own Moon does with Earth. The mean orbital distance is 1,070,400 KM / 664,718 miles from Jupiter.
Ganymede orbits Jupiter at an average a speed of 10.88 KPS / 6.76 MPS or 39,168 KPH / 24,323 MPH.
Ganymede is 5,269 KM / 3,273 miles in diameter & is the largest and most massive moon in the entire solar system. Ganymede is larger than the planets Mercury, Eris and Pluto, though has only about 45% of the mass of Mercury, but is approximately 12 times more massive than Pluto and 10 times more massive than Eris.
Ganymede has an average density of 1.94 grams per cubic centimetre, roughly 50% ice, 50% rock / metal. There is a fairly large iron core most likely 1,000 KM / 621 miles wide, with a silicate rich mantle and an ice crust with a postulated 800 KM / 497 mile deep subsurface salty ocean.
The average surface temperature on Ganymede is minus 163 Celsius / minus 261 Fahrenheit or 110 Kelvin. The minimum at the poles are around minus 210 Celsius / minus 364 Fahrenheit or 63 Kelvin. The ice surface is almost as hard as rock at these temperatures.
Ganymede has huge ridges and dark, cratered regions. There are cryovolcanic features, that erupted slushy ices. There is a frost cap around the north polar region.
Ganymede is the only moon in the solar system that generates its own global magnetosphere, with gravity data suggesting that Ganymede like Earth and the planet Mercury has a dual layered core, a solid iron inner core and a molten iron sulphide outer core.
Text: Andrew R Brown.
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Royal Astronomical Society of New Zealand
eNewsletter: No. 229, 20 January 2020
Affiliated Societies are welcome to reproduce any item in this email newsletter or on the RASNZ website www.rasnz.org.nz in their own newsletters provided an acknowledgement of the source is also included.
Contents
1. Betelgeuse Unusually Faint
2. Annual General Meeting Deadlines
3. Subscriptions and Reports Due
4. The Solar System in February
5. 2020 Conference and RASNZ Centenary
6. Call for Papers for 2020 RASNZ Conference
7. Star Parties in 2020
8. Variable Star News
9. Denis Sullivan
10. Australite Tektite Crater Found?
11. A Second Planet around Proxima Centauri?
12. Quasar Imaging Tests Dark Matter and the Hubble Constant
13. How to Join the RASNZ
14. Gifford-Eiby Lecture Fund
15. Quotes
1. Betelgeuse Unusually Faint
The bright star Betelgeuse has faded to a historic low. Currently Betelgeuse is in the north at dusk. It is the orange star directly below and right of the line of three stars making Orion's belt, or the bottom of the 'The Pot' in our southern hemisphere view.
On the list of brightest stars, Betelgeuse ranks 10th. But that’s only an average. The star's brightness typically varies from magnitude 0.2, roughly like Rigel, the bluish-white star above Orion's belt, to about 1.3. That's only a few tenths of magnitude brighter than Bellatrix (magnitude 1.6), the star to the left of Betelgeuse. (Bellatrix and Rigel are also variable stars, but they vary less in brightness than Betelgeuse does.)
As recently as October, Betelgeuse was around magnitude 0.5, considerably brighter than Aldebaran (0.9), the orange star below and left of Betelgeuse. But in December there was a steep drop in brightness. On December 28 it was estimated to be magnitude of 1.5, nearly equal in brightness to Bellatrix. In just two months it's fallen from 10th place to 21st, according to astronomer James Kaler's 26 Brightest Stars list, a remarkable decline — and a historic low.
Betelgeuse is a pulsating red supergiant. It physically expands and contracts as its atmosphere alternately traps and releases heat radiating from its core. When the star is smallest and hottest, it would extend to the orbit of Mars if put in place of the Sun. When largest and coolest it would balloon to span Jupiter's orbit. Although Betelgeuse is 20 times more massive than the Sun, its expanding shell has only 1/10,000 the density of air — it might be better described as a red-hot vacuum.
Betelgeuse is a semi-regular variable star with multiple periods of variation. The primary pulsations repeat every ~425 days, but the star also shows additional changes in brightness with periods of 100-180 days and 5.9 years. Dark patches that resemble monstrous sunspots as well as bright blobs of upwelling gas are behind some of these fluctuations. Betelgeuse is clearly in upheaval and will continue to surprise us before it eventually runs out of fuel, collapses, and explodes as a Type II supernova.
While the supergiant's current behaviour is out of the ordinary, it doesn't necessarily mean an eruption is imminent. Astronomers predict a star-shredding blast sometime in the next 100,000 years or so.
Astronomers Edward Guinan and Richard Wasatonic, both at Villanova University, along with amateur Thomas Calderwood, have been monitoring the star for more than 25 years. They reported a decline to magnitude 1.29 on December 20th using precise V-band photometry, making this the faintest minimum since the star was first monitored electronically in the early 20th century.
In Astronomical Telegram #13365 Guinan writes: "The current faintness of Betelgeuse appears to arise from the coincidence of the star being near the minimum light of the ~5.9-yr light-cycle as well as near the deeper than usual minimum of the ~425-d period." In effect, the star's overlapping cycles have created a sort of superminimum. Guinan encourages observers to closely monitor the star during this unusually cool and faint state.
Anyone can follow Betelgeuse's brightness changes. Use Bellatrix (magnitude 1.6) and Aldebaran (0.9) to determine its brightness to an accuracy of one-tenth of a magnitude. For instance, if Betelgeuse appears midway in brightness between Bellatrix and Aldebaran its magnitude would be about 1.3. If a little fainter or brighter one way or the other add or subtract additional tenths of a magnitude.
When making a magnitude estimate look quickly from star to star. If you stare too long, your brain will "inflate" a star's brightness. Near-sighted observers have an additional tool at their disposal. Just take off your glasses! The stars will expand into disks, making it easier to detect subtle brightness differences.
Then write that number down and return every few nights or maybe every week and make another estimate. Over time you’ll see it change right before your eyes. Betelgeuse is expected to continue fading into January and then re-brighten, but you never know what surprises may still be in store. Stars do as they please and that's half the fun.
[On January 19th Betelgeuse was about the same brightness as Bellatrix, so about magnitude 1.6. -- Ed.]
-- Abridged from Bob King's article of December 31 at https://www.skyandtelescope.com/observing/fainting-betelgeuse/
What’s Up With Betelgeuse?
For speculations on Betelgeuse becoming a supernova see, among others:
https://globalnews.ca/news/6414358/betelgeuse-dying-supernova/
https://www.economist.com/science-and-technology/2020/01/11/might-there-soon-be-a-supernova-near-earth
2. Annual General Meeting Deadlines
Nominations for RASNZ Council positions.
The executive positions are: President, Vice President, Executive Secretary, and Treasurer. The immediate Past President is an ex-officio position.
Five Councillors are elected by members. Two Councillors are appointed by the Affiliated Societies Committee. One Councillor is elected by the Fellows.
All nominations must be sent to the Executive Secretary (see below) by 8th February 2020. A nomination form was included in the recent Keeping in Touch #35, 17th December.
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Notices of motion for Annual General Meeting must be submitted to the Executive Secretary by Saturday, 28th March.
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Nominations for RASNZ awards and prizes -
• MURRAY GEDDES MEMORIAL PRIZE - Nominations must be made by March 8th. See By-Law G5.
• EARTH & SKY BRIGHT STAR AWARD - for contributions in NZ in promoting astronomy to the public, or in astronomical education, or in promoting dark skies. Nominations by 8th February.
• FELLOWS NOMINATION - nominations by February 8th. See Rules 14-23.
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For a link to the RASNZ rules see - https://www.rasnz.org.nz/images/articleFiles/Council/Rules2019.pdf
The Executive Secretary's email address is
John Drummond
Postal address: John Drummond, PO Box 113, Patutahi 4045.
3. Subscriptions and Reports Due
2020 RASNZ subscriptions are due on the 1st January. See - https://www.rasnz.org.nz/rasnz/payments-and-donations
Section and Group reports are due with the Executive Secretary by 9th March. For more details see By-Laws F1 - F16.
4. The Solar System in February
Dates and times shown are NZDT (UT + 13 hours). Rise and Set times are for Wellington. They will vary by a few minutes elsewhere in NZ. Data is adapted from that shown by GUIDE 9.1
THE SUN and PLANETS in February, Rise & Set, Magnitude & Constellation.
February 1 NZDT February 29 NZDT
Mag Cons Rise Set Mag Cons Rise Set
SUN -26.7 Cap 6.23am 8.44pm -26.7 Aqr 6.58am 8.07pm
Merc -1.0 Cap 7.35am 9.28pm -1.0 Aqr 6.38am 7.33pm
Venus -4.0 Aqr 9.50am 10.28pm -4.1 Psc 10.47am 9.44pm
Mars 1.6 Oph 2.17am 5.24pm 1.4 Sgr 1.48am 5.00pm
Jup -1.8 Sgr 4.03am 7.05pm -1.9 Sgr 2.40am 5.37pm
Sat 0.5 Sgr 4.58am 7.46pm 0.6 Sgr 3.23am 6.06pm
Uran 5.7 Ari 1.18pm 12.02am 5.8 Ari 11.32am 10.13pm
Nep 7.9 Aqr 9.26am 10.17pm 7.9 Aqr 7.41am 8.29pm
Pluto 14.6 Sgr 4.47am 7.44pm 14.6 Sgr 3.01am 5.57pm
February 1 NZDT February 29 NZDT
Twilights morning evening morning evening
Civil: start 5.55am, end 9.13pm start 6.32am, end 8.34pm
Nautical: start 5.17am, end 9.51pm start 5.59am, end 9.07pm
Astro: start 4.35am, end 10.33pm start 5.23am, end 9.42pm
February PHASES OF THE MOON, times NZDT & UT
First quarter: Feb 2 at 2.42pm (01:42 UT)
Full Moon: Feb 9 at 8.33pm (07:33 UT)
Last quarter Feb 16 at 11.17am (Feb 15, 22:17 UT)
New Moon: Feb 24 at 4.32am (Feb 23, 15:32 UT)
PLANETS in FEBRUARY
MERCURY is in the early evening sky most of February. At first it sets 40 to 45 minutes after the Sun, so will be a difficult object in the evening twilight. The planet is at greatest elongation, 18° east of the Sun on the 10th. It is stationary on the 16th and at inferior conjunction, between the Earth and Sun, on the 26th. Following conjunction, Mercury becomes a morning object but rises only a few minutes before the Sun by the 29th.
VENUS is an evening object setting about 90 minutes after the Sun. It is in Pisces most of the month. Venus will be fairly low and a little to the north of west shortly after sunset. On the 27th the crescent moon will be 7° to the upper left of Venus.
MARS, JUPITER and SATURN are all morning objects, forming a steeply inclined line to the east with Mars highest and Saturn lowest. They get closer to one another during the month. By the end of February the separation of Mars from Jupiter will be 11° with Saturn 8.5° below Jupiter. The three will be a little to the south of east. The crescent moon passes the three planets on the mornings of February 19, 20 and 21 respectively. Occultations of Mars and Jupiter by the moon are not visible from NZ.
PLUTO is between Jupiter and Saturn, closer to the latter.
URANUS is an evening object setting a little after 11pm at the end of February. By then NEPTUNE sets only 20 minutes after the Sun.
POSSIBLE BINOCULAR ASTEROIDS in FEBRUARY
February 1 NZDT February 29 NZDT
Mag Cons transit Mag Cons transit
(1) Ceres 9.1 Cap 12.49pm 9.3 Cap 11.46am
(4) Vesta 8.0 Ari 7.36pm 8.3 Tau 6.13pm
(5) Astraea 9.3 Cnc..12.35pm 10.0 Gem 10.32pm
CERES is a low morning object just over 7° to the lower right of Saturn on the 1st. Their distance apart doubles by the 29th as the faster moving asteroid draws away from the planet.
VESTA is an evening object. It moves into Taurus at the end of February when it will be about 10° from the Pleiades.
ASTRAEA fades from 9.3 to 10 during the month. It is likely to be lost to binocular view by mid-February.
-- Brian Loader
5. 2020 Conference and RASNZ Centenary
It is a pleasure to announce that the next conference of the Royal Astronomical Society of New Zealand (RASNZ) will be held at the Wharewaka Function Centre on Wellington waterfront over the weekend of 8 - 10 May 2020. The Wellington Astronomical Society is hosting the Conference.
This year is the 100th anniversary of the formation of the Society and to honour this special occasion we will be welcoming four invited speakers. They will be Dr Dom Pesce (Black Hole Initiative, Harvard University), Professor Anna Scaife and Dr Rene Breton (Manchester University/Jodrell Bank) and Dr Chris Lintott (Oxford University). This year the Fellows´ Lecture will be given by long standing Society member and past president John Drummond. Titles and abstracts for these talks will be released when they are available.
As the programme will commence at the earlier than usual time at 1pm on Friday we encourage as many as possible to make their travel arrangements to arrive in the city during the morning.
The conference will be preceded by a Dark Sky Workshop on the morning of
Thursday 7 May. The workshop will consist of short talks on relevant key local and international dark sky updates and discussion/demonstration on topics such as sky quality measurements and dark sky friendly lighting.
The RASNZ website now has available the conference brochure, on-line registration (and downloadable form) and paper submission (via the registration page). See it all here: http://www.rasnz.org.nz/groups-news-events/rasnz-conference.
Please consider participating in this Conference as RASNZ celebrates its centenary - we look forward to seeing you there.
-- Glen Rowe, Chair, Standing Conference Committee.
6. Call for Papers for 2020 RASNZ Conference
The RASNZ Standing Conference Committee (SCC) invites and encourages anyone interested in New Zealand astronomy to submit oral or poster papers, with titles and abstracts due by 1 April 2020 or until such time as the SCC deems the conference programme to be full. The link to the paper submission form can be found on the RASNZ Conference website http://rasnz.org.nz/groups-news-events/rasnz-conference. Please note that you must be registered for the conference to give an oral presentation, and for your convenience a link has been provided if you wish to do this when you submit a paper.
We look forward to receiving your submissions and seeing you at the conference. Please feel free to forward this message to anyone who may find it of interest.
For further information on the RASNZ Conference, registration details and associated events please visit the conference website at http://rasnz.org.nz/groups-news-events/rasnz-conference.
-- Warwick Kissling, RASNZ Standing Conference Committee
7. Star Parties in 2020
The following star parties are planned for 2020:
Stardate North Island: Friday February 21st to Sunday 23rd at Stonehenge, Carterton. Check Phoenix website - http://www.astronomynz.org/
Stardate South Island: Friday February 21st to Sunday 23rd, at Staveley, South Island. Keep an eye on https://cas.org.nz/
Stargazers Getaway 2020 Camp Iona, Friday September 18th to Sunday 20th. This is new Moon, so we are targeting this weekend for dark skies! See
https://www.facebook.com/events/943327669369996/
NACAA: The 29th NACAA conference will be held in the NSW (Australia) regional city of Parkes (where the world-famous Parkes Radio Telescope is) over the 2020 Easter weekend, Friday April 10th – Monday 13th. For more details see http://nacaa.org.au/2020/about
-- Mostly from 'Keeping in Touch' #34, 27th Sept 2019.
8. Variable Star News
VSS Symposium 6
The next Variable Stars South Symposium is to be held in association with the National Australian Convention of Australian Astronomers (NACAA), Easter 2020 at Parkes (site of the famous large steerable dish Radio Telescope). VSSS6 will be held on Friday, April 10th, 2020. There is usually an informal get together on the evening prior. An outline of the format is given in the Oct. 2019 newsletter (available under Community on the VSS website.) The next VSS newsletter is due for publication towards the end of January and should contain more information on the event.
The website for the NACAA event is https://nacaa.org.au/2020/about. The NACAA conference is over three days, Saturday to Monday, and information on the programme is available there.
Irregular Variations
A recent AAVSO Alert Notice, No 691, called for urgent monitoring of ASASSN-V J060000.76-310027.83 in the southern constellation of Columba (The Dove). This star is normally visual magnitude 13.6 but has undergone a small but unexpected fade. The discovery was made with the All Sky Automated Survey (ASAS-SN) operated by Ohio State University. The star is a nearby (d~155 pc) K5 dwarf star. At the time of the announcement (8 Jan 2020) the cause of the fading could not be identified; it has been suggested it may be due to a dust cloud around an unknown companion. Urgent photometry was called for; refer to the alert notice for guidelines.
For those interested in notices of transient phenomena, advice of alerts is being posted by Mark Blackford on the VSS Google Discussion Group.
The bright star Betelgeuse in Orion (alpha Orionis) hit the news headlines in December with the announcement that it was experiencing an unusually deep fade described as a possible prelude to a supernova in our immediate star neighbourhood. The media has moved on but not surprisingly the star is receiving close attention from a large number of observers. The star is normally at V mag 0.5 and a decrease is normally 0.3 mag. to something above magnitude 1.0 at most, a very small decrease (magnitudes quoted are V-filter). At the time of writing (16th Jan) the brightness is about mag. 1.5 and there is no indication that the star has reached its minimum brightness. The steep decline is very different to the normal shallow oscillation. It will be interesting to see at what point the decline flattens out. Observing is best done by experienced observers as reddish stars are difficult to assess visually and because of the brightness comparison stars are limited.
-- Alan Baldwin
9. Denis Sullivan
RASNZ Fellow Denis Sullivan died at his home on Christmas day after a brief illness.
The following is from a tribute by John Lekner of Victoria University of Wellington, forwarded by Pauline Harris.
Denis joined the Physics Department in 1968, so we have lost our longest-serving physicist. He was born and educated in Sydney, first as an engineer (it showed: he had a lifelong appreciation, even love, of good tools and clever devices, and was very good at implementing the electronics of data collection). He changed to physics and went to ANU for graduate study, where he met Whetu Tirikatene. They married and came to Wellington because of Whetu's political connections, and Denis got a job at the Institute of Nuclear Sciences, later to form a part of the current GNS, and then as lecturer at Vic. His graduate training was in nuclear physics, and he first worked on electron-positron annihilation, but then joined David Beaglehole and Joe Trodahl in what was for all of them a new venture: astronomy. Both David and Joe eventually went back to their condensed matter research, while Denis prospered in his new-found field, building up astronomy courses and continuing observational astronomy. His research interests included pulsating white dwarfs, microlensing, and most recently extra-terrestrial planets. This year's Nobel Prize was awarded for the detection of the earliest known extra-terrestrial planets. Currently there are about four thousand known, but when Denis joined the field there was only a handful. Denis happened to be at the Mauna Kea observatory in Hawaii when the position of one of the possible early ones was circulated among astronomers. Denis and Tiri (at the time his graduate student) were able to independently confirm, by a different observational method, the existence of that planet, about number 3 or 4 at the time. So Denis was in at the beginning of what is now almost an astronomical industry.
Denis was an excellent teacher: I have some of his astronomical notes, which are so meticulous and clear they are a pleasure to read. He was a very good speaker also, with a lovely sense of humour. His tolerance of bureaucracy was notably low; likewise of any kind of pretence or dishonesty. I came to value his opinion on political and historical matters, as well as on physics. He had practical wisdom, balance, generosity. It is a privilege to have been his colleague.
10. Australite Tektite Crater Found?
Tektites are small (generally less than 5 cm across) glassy objects found in several parts of the world. They have aerodynamic shapes, teardrop and similar, showing that they have been heated by passing through the atmosphere. They are the 'splash' from big meteorite impacts. Molten rock has been ejected into space then fallen back to Earth, being heated a second time coming through the air. They are found in several parts of the world. Some have been identified with major impact craters.
The youngest and largest 'strewn field' of tektites extends from southern China across southeast Asia and Australia to the edge of Antarctica. Some have been found as far west as Africa. They are variously known as Australites, Indochinites, Philippinites and other names and are around 790,000 years old. Their source crater hasn't previously been identified.
Now, researchers think they've found the crater responsible buried under the Bolaven Plateau, a sandstone and mudstone plateau in southeastern Laos that's covered in hardened lava up to 300 metres thick.
The Bolaven crater “is likely the largest crater (on Earth) formed within the past million years,” says study lead Kerry Sieh (Earth Observatory Singapore). The recent crater reported under the Greenland ice sheet is larger, he adds, but its age is still unclear.
In a study appearing December 30th in the Proceedings of the U.S. National Academy of Sciences, Sieh and colleagues laid out four individual lines of evidence pointing to the existence of a crater under the Bolaven Plauteau as the source of the Australasian strewn field.
The researchers first tested the tektite fragments themselves, to see if they contained basalts, which would indicate their origin on the volcanic plateau. Then they tested the proposed impact site, dating the basalts there and mapping the region's density to look for evidence of a buried impact crater. Indeed, mapping of gravitational anomalies in the area showed hints of a 17 km by 13 km crater buried beneath the volcanic plain in southeastern Laos.
"Now that we know the site of the impact, we can begin to investigate how the surrounding areas were affected by the impact,” says Sieh. “For example, how thick and coarse was the ejecta blanket, 10, 50 300 km away?” From this, he says, we can understand the effect of the shock wave that blasted outward after the impact.
The object that made the crater was likely a 2-km wide asteroid that came in at a shallow angle, gouging out the 17-km wide crater and showering the surrounding region with debris. While the impactor was 30 times smaller than the one that caused the Chicxulub extinction event 66 million years ago, it was 100 times bigger than the more recent bolide that exploded over Chelyabinsk, Russia, in 2013.
Intriguingly, the sedimentary layer where geologists find Australasian tektites, which is 790,000 years old, overlaps with the timeframe of the sediments in which the 770,000-year-old Peking Man (Homo erectus) was found. Maybe early hominids witnessed this catastrophic event!
For maps and images see David Dickinson's article at https://www.skyandtelescope.com/astronomy-news/new-location-proposed-for-australasian-strewn-field-source-crater/
from which most of the above was taken.
11. A Second Planet around Proxima Centauri?
Less than four years after the discovery of a planet orbiting our closest neighbouring star, Proxima Centauri, scientists think they’ve discovered a second world in the same system.
The planet, a super-Earth called Proxima Centauri c (Proxima c for short), has at least six times more mass than Earth and orbits its star every 5.2 years. The discovery appears January 15th in the open-access journal Science Advances.
The first planet to be discovered in this system, Proxima b, initially raised astronomers’ hopes: The Earth-size planet orbits Proxima Centauri every 11.2 days, putting it in the so-called habitable zone, where liquid water may exist on a rocky surface. However, further study has showed that the magnetically active star likely robbed the planet of its atmosphere long ago.
To find the new super-Earth, scientists used the HARPS spectrograph at the La Silla Observatory and the UVES spectrograph on the Very Large Telescope, both in Chile. Mario Damasso (Astrophysical Observatory of Torino, Italy) and colleagues analyzed data collected between 2000 and 2017, looking for the signature “wobble” in Proxima’s Centauri’s light spectrum that would indicate the presence of a planet, the same technique that enabled scientists to confirm the Proxima b’s presence in 2016.
“Stars like Proxima Centauri are rather restless and continuously present eruptions and spots on their surface, which make the detection of a planetary-induced oscillation very complicated,” says coauthor Fabio Del Sordo (University of Crete and Foundation for Research and Technology-Hellas in Heraklion, Greece). Because the observations span almost two decades, the scientists have confidently ruled out those sources of noise, but they caution that follow-up observations are needed to confirm that the signal comes from a planet.
Proxima c is about 1.5 astronomical units (a.u.) away from its star — just a little farther out than Earth is from the Sun, but about 30 times farther out than Proxima b. Because of this large distance, even if the planet were rocky, it would be too cold to host life as we know it.
The planet’s existence challenges theories explaining the formation of super-Earths. Scientists think that super-Earths like Proxima c should form near a snowline — the region where gaseous compounds such as water, carbon monoxide, or ammonia solidify into ices. These regions are sweet-spots for super-Earth formation, yet this planet orbits much farther out than the snowlines in its system.
It’s also unlikely that the planet would have formed close to its star only to be kicked farther out, because planet searches indicate that there are no massive planets on closer orbits that could have done the kicking.
Future observations with observatories ranging from the space-based Gaia mission to the submillimeter-wavelength ALMA dishes will help confirm the planet’s existence and explain the planet’s formation.
See Julie Freydlin's original article at https://www.skyandtelescope.com/astronomy-news/proxima-centauri-c-second-planet-nearest-star-system/
12. Quasar Imaging Tests Dark Matter and the Hubble Constant
The Hubble Space Telescope, which will celebrate its 30th birthday this April, has imaged cosmic mirages that yield two remarkable cosmological results. One constrains the nature of dark matter, the other further deepens the controversy about how fast the universe is currently expanding. Two teams of astronomers presented the two results at a meeting of the American Astronomical Society in Honolulu.
The two Hubble breakthroughs stem from meticulous observations of gravitational lenses – a kind of cosmic mirage created when gravity bends light. In these cases, the background light comes from a quasar, the luminous core of a galaxy containing a supermassive black hole. General relativity explains how a massive foreground galaxy — if it’s aligned just right — can split the light from such a quasar into four individual images. Moreover, gravitational lensing may enhance the apparent brightness of these images. Astronomers can then study the mirage, sometimes called an Einstein’s Cross, to measure fundamental properties of the universe.
In the first study, led by Anna Nierenberg (NASA/Jet Propulsion Laboratory), Hubble studied eight quasars, whose light has travelled some 10 billion years; each one is quadruply lensed by a foreground galaxy about five times closer.
Based on the lens geometry, astronomers can calculate the expected relative brightness of the four images. But such calculations assume that mass is smoothly distributed throughout the lens halo. In reality, however, the light-bending effects of dark matter clumps in the lens galaxy’s halo will change these expected values.
The number and dimensions of these dark matter clumps strongly influence the relative brightnesses of the quasar images. The Hubble data indicate that the dark matter clumps tend to be relatively small, just one-hundred-thousandth the total mass of our Milky Way galaxy.
The result rules out the existence of warm dark matter, the idea that dark matter consists of “warm” (fast-moving) particles. Some cosmologists have suggested that dark matter might be warm because dark matter searches for cold (or more slowly moving) particles have turned up empty. But fast-moving particles have a hard time clumping together in small, low-mass concentrations.
According to Nierenberg, the Hubble observations constitute the strongest evidence yet for cold, low-velocity dark matter. The results were published in the December 24th Monthly Notices of the Royal Astronomical Society and also appearon the arXiv preprint server.
https://arxiv.org/abs/1908.06983
In the second study, astronomers on the team known as H0 Lenses in COSMOGRAIL’s Wellspring (H0LiCOW) focused on the “flickering” of quadruply lensed quasars.
True luminosity variations of the quasar — most likely caused by the varying activity of the central black hole — show up at different times in the four images. That’s because to produce each image, the quasar’s light follows a different path to the observer, and each path is a slightly different length. The time delays for the longer paths, combined with a map of the way mass is distributed in the foreground galaxy, yield a unique three-dimensional picture of the gravitational lens. As a result, astronomers can measure precise distances to both the quasar and the lensing galaxy. Moreover, these values are completely independent of other distance measures.
Distances are crucial for measuring the current expansion rate of the universe. Astronomers typically estimate a galaxy’s distance by its redshift, which measures how the wavelength of light stretches as it traverses expanding space. But to understand how fast space is expanding, astronomers need a distance measure that’s independent of redshift — that’s what the lensed quasars provide.
The H0LiCOW team uses the new Hubble data to obtain the most precise value of the current expansion rate yet obtained from gravitational lens studies: 73 km per second per megaparsec, with an uncertainty of 2.4 percent. (A megaparsec is 3.2 million light years.)
This value stands firmly on one side of an ongoing debate on how fast the universe is currently expanding. Estimates based on objects in the relatively nearby universe show the current expansion rate, termed the Hubble Constant, to be 74 km/s/Mpc. However, the dark energy-cold dark matter theory that successfully models the composition and evolution of the universe, combined with precise measurements of the cosmic microwave background emitted shortly after the Big Bang, puts the Hubble Constant at 67 km/s/Mpc.
The H0LiCOW collaboration analysed six multiply-imaged quasar systems, measuring the current expansion rate of the universe to be between 71.5 and 75 km/s/Mpc. This value is inconsistent with estimates obtained from modelling of the cosmic microwave background.
Folding in the results from the gravitational lensing study, the tension is so strong, says team member Geoff Chih-Fan Chen (University of California, Davis), that the term “crisis” is fully justified.
The H0LiCOW team, led by Sherry Suyu (Max Planck Institute for Astrophysics, Germany), will publish these latest results in the Monthly Notices of the Royal Astronomical Society. A preprint is available on the arXiv server https://arxiv.org/abs/1907.04869
-- Govert Schilling's article with images and diagrams at https://www.skyandtelescope.com/astronomy-news/hubble-sheds-light-on-dark-matter-and-cosmic-expansion/
13. 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 treasurer@rasnz.co.nz or
by completing the online application form found at
http://rasnz.org.nz/rasnz/membership-application
Basic membership for the 2019 year starts at $40 for an ordinary
member, which includes an electronic subscription to our journal
'Southern Stars'.
14. Gifford-Eiby Lecture Fund
The RASNZ administers the Gifford-Eiby Memorial Lectureship Fund to
assist Affiliated Societies with travel costs of getting a lecturer
or instructor to their meetings. Details are in RASNZ By-Laws Section
H and at http://rasnz.org.nz/rasnz/ge-fund
The application form is at
http://rasnz.org.nz/Downloadable/RASNZ/GE_Application2019.pdf
15. Quotes
"This morning around 13 hours a huge comet appeared in the sky, and fell toward Earth making the whole sky shine with fire, followed by a great noise as of thunder that was felt throughout the whole province, and the fire and splendour were similarly seen throughout the entire territory." -- A note by a parish priest at a small town in what is now the Province of Brescia, Northern Italy, describing a daylight fireball on 24 January 1680. Found in archives a few months ago. See http://neo.ssa.esa.int/ .
"Physics is the law. Everything else is a recommendation." -- Elon Musk quoted in 'NZ Listener' December 14, 2019, p.6.
"We are all ignorant. We are just ignorant about different things." -- Will Rogers quoted in Michael Collins's book "Carrying the Fire".
Alan Gilmore Phone: 03 680 6817
P.O. Box 57 alan.gilmore@canterbury.ac.nz
Lake Tekapo 7945
New Zealand
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