Astronomy_News_20_04_2021
Astronomy_News_20_04_2021
This months research Papers 20_04_2021
RASNZ_20_04_2021
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
Google Group
https://groups.google.com/g/nzastrochat
Astronomy in Wellington
https://www.facebook.com/groups/11451597655/
Blogger Posts
http://laintal.blogspot.com/
Reddit
https://www.reddit.com/user/Edwin_Rod_NZ
Quaroa
https://www.quora.com/q/astronomyinnewzealand
Twitter
https://twitter.com/Laintal
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Research papers
Interactions between collapsed bodies and the Solar system
https://arxiv.org/abs/2103.12745
Two Bright M Dwarfs Hosting Ultra-Short-Period Super-Earths with Earth-like Compositions
https://arxiv.org/abs/2103.12760
Anoxic Atmospheres on Mars Driven by Volcanism
https://arxiv.org/abs/2103.13012
The Curious Case of Argon
https://arxiv.org/abs/2103.15071
Evening home lighting adversely impacts the circadian system and sleep
https://www.nature.com/articles/s41598-020-75622-4
Earth's carbon deficit caused by early loss through irreversible sublimation
https://arxiv.org/abs/2104.02702
Quantifying the Classification of Exoplanets
https://arxiv.org/abs/2104.02991
Five carbon- and nitrogen-bearing species in a hot giant planet's atmosphere
https://arxiv.org/abs/2104.03352
Asteroids Were Born Big
https://arxiv.org/abs/0907.2512
Water in star-forming regions
https://arxiv.org/abs/2102.02225
Main ways in which stars influence the climate and surface habitability of their planets
https://arxiv.org/abs/2104.06391
How likely are Snowball episodes near the inner edge of the habitable zone
https://arxiv.org/abs/2104.06216
Injection of Inner Oort Cloud Objects Into the Distant Kuiper Belt by Planet Nine
https://arxiv.org/abs/2104.05799
Significant interstellar object production by close stellar flybys
https://arxiv.org/abs/2104.06845
Recovery of Spectra of Phosphine in Venus' Clouds
https://arxiv.org/abs/2104.09285
Tidal Effects on the Radial Velocities of V723 Mon
https://arxiv.org/abs/2103.05216
The effect of core formation on surface composition and planetary habitability
https://arxiv.org/abs/2104.10612
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Interesting News items
New theory suggests large blobs of material in Earth's mantle are remnants of protoplanet Theia
https://phys.org/news/2021-03-theory-large-blobs-material-earth.html
A very good look at lights
https://www.stuff.co.nz/life-style/well-good/300254567/how-energysaving-led-lights-disrupt-our-sleep
Planety Boundaries
https://news.mongabay.com/2021/03/the-nine-boundaries-humanity-must-respect-to-keep-the-planet-habitable
Alien life is out there
https://theconversation.com/alien-life-is-out-there-but-our-theories-are-probably-steering-us-away-from-it-124042
with darkness
https://www.eventfinda.co.nz/2021/within-the-hours-of-darkness/masterton
Trio of Fast-Spinning Brown Dwarfs May Reveal a Rotational Speed Limit
https://www.jpl.nasa.gov/news/trio-of-fast-spinning-brown-dwarfs-may-reveal-a-rotational-speed-limit
If Planet Nine Is Out There, It May Not Be Where We Think
https://www.sciencealert.com/if-planet-nine-is-out-there-it-may-not-be-where-we-think
The Inner Oort Cloud Connection
https://findplanetnine.blogspot.com/2021/04/the-inner-oort-cloud-connection.html
Injection of Inner Oort Cloud Objects Into the Distant Kuiper Belt by Planet Nine
https://arxiv.org/abs/2104.05799
A New Super-Earth Detected Orbiting A Red Dwarf Star
http://spaceref.com/exoplanets/a-new-super-earth-detected-orbiting-a-red-dwarf-star.html
First flight
https://www.jpl.nasa.gov/news/nasas-ingenuity-mars-helicopter-succeeds-in-historic-first-flight
Proxima Flare Captured at Multiple Wavelengths
https://www.centauri-dreams.org/2021/04/23/proxima-flare-captured-at-multiple-wavelengths/
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Updates from Andrew B,
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RASNZ
Dear RASNZ members,
This is a friendly reminder that the two month prior to the RASNZ AGM deadline for the Murray Geddes and Dark Sky Bright Star awards is fast approaching. The deadlines are the 11th May 2021. If you wish to nominate someone for either award, please send me the completed nomination form (attached).
The rules are -
G. MURRAY GEDDES MEMORIAL PRIZE
G1. The Murray Geddes Memorial Prize shall be awarded to a person or persons at intervals of
not more than five years, nor less than one year, for contributions to astronomy in New
Zealand.
G2. The recipient of the prize shall be a resident of New Zealand and need not be a member of
the Society.
G3. Only in exceptional circumstances shall the award be made to the same person more than
once.
G4. Council may annually, at such time as it may decide, invite nominations for the prize from
whatever sources it deems appropriate. Nominations shall remain valid for three years from
the date of nomination. Additional information in support of a nomination may be accepted
during the three years.
G5. Council shall have the sole decision in making the award and its decision shall be made not
less than two months before the date of the Annual General Meeting.
G6. The prize shall consist of a medallion which shall be presented with a certificate suitably
inscribed with the recipient's name and the signature of the President or Vice President.
The prize and certificate shall be presented, whenever possible, at the Annual General
Meeting or Conference.
G7. The name of each new recipient shall be published in the Journal of the Society.
K. DARK SKY PROJECT BRIGHT STAR AWARD
K1. The Dark Sky Project Bright Star award shall be awarded to a person or persons at intervals
of not more than five years nor less than one year, for contributions in New Zealand in
promoting astronomy to the public, or in astronomical education, or in promoting dark
skies so as to allow astro-tourism to flourish.
K2. The recipient of the award shall be a resident of New Zealand of at least three years’
standing and need not be a member of the Society.
K3. Only in exceptional circumstances shall the award be made to the same person more than
once.
K4. Council may annually, at such time as it may decide, invite nominations for the award from
whatever sources it deems appropriate. Nominations shall remain valid for three years
from the date of nomination. Additional information from the date of nomination may be
accepted during the three years.
K5. Council shall have the sole decision in making the award and its decision shall be made not
less than two months before the date of the Annual General Meeting.
K6. The award shall consist of goods to be determined at the discretion of the representative(s)
of the Dark Sky Project, and shall be presented with a certificate suitably inscribed with the
recipient’s name and the signatures of the President of the Society and of a representative
of the Dark Sky Project. The award shall be presented, whenever possible, at the Annual
General Meeting or Conference.
K7. The name of each new recipient shall be published in the Journal of the Society
Regards
John Drummond
RASNZ Executive Secretary
==============================
Royal Astronomical Society of New Zealand
eNewsletter: No. 244, 20 April 2021
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. 2021 RASNZ Conference and Annual General Meeting
2. Call for Papers for 2021 RASNZ Conference
3. The Solar System in May
4. Variable Star News
5. New Zealand Astrophotography Competition
6. Aotearoa Astrotourism Academy -- September 10-12
7. Black Hole's Magnetic Field Imaged
8. Star Formation Puzzle
9. Pristine Comet Borisov
10. How to Join the RASNZ
11. Quote
1. 2021 RASNZ Conference and Annual General Meeting
The 2021 RASNZ Conference and Annual General Meeting will take place in
Wellington this year, 100 years after the first Annual meeting of the
Astronomical Society of New Zealand (ASNZ) which was also held in
Wellington. Last year's cancelled face to face conference would have
celebrated the Centenary of the formation of the ASNZ/RASNZ.
The Wellington Astronomical Society are again hosting this year's
conference which will take place over the weekend of 9th to 11th of July
2021. A Dark Sky Workshop is planned for the morning of Monday 12th of
July. The Conference will be held in the Wharewaka Function Centre,
situated on Wellington’s waterfront near Te Papa.
Registration
An on-line registration form is available by following the link to the
conference page from
https://www.rasnz.org.nz/groups-news-events/rasnz-conference
<https://www.rasnz.org.nz/groups-news-events/rasnz-conference>. A
downloadable registration form is also available at the same link. Final
date for registration is the 27th of June 2021.
Conference fees are as follows:
$275 (Members)
$305 (Non-members)
$155 (Saturday only)
Dinner: $100 per person
Dark Sky Symposium $ 30
Paper submission
The organisers invite and encourage anyone interested in New Zealand
astronomy to submit oral or poster papers for the conference programme.
Please note that those presenting
papers must also register for the conference. An on-line submission form
is available by following the link to the conference page from
https://www.rasnz.org.nz/groups-news-events/conf-next
<https://www.rasnz.org.nz/groups-news-events/conf-next>. Titles and
abstracts are due by 1 June 2021
The RASNZ Council and Conference Committee and the Local Organising
Committee look forward to catching up with you all after a longer than
normal break between conferences. We have a lot to celebrate and will
have a strong group of Students With A Passion for Astronomy present to
help RASNZ move into its second 100 years.
--Steve Butler, President, RASNZ
2. Call for Papers for 2021 RASNZ Conference
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 9 - 11 July 2021. This year the Fellows’ Lecture will be given by long standing Society member and past president John Drummond. The guest speaker will be Dr Heloise Stevance from the University of Auckland. Titles and abstracts for these talks will be released when they are available.
The conference will be followed by a Dark Sky Workshop on the morning of Monday 12 July. 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 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 June 27th 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. The time allocated for each speaker is 20 minutes, including time for questions
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 & Steve Butler, RASNZ Standing Conference Committee
3. The Solar System in May
Dates and times shown are NZST (UT + 12 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 MAY, Rise & Set, Magnitude & Constellation
May 1 NZST May 31 NZST
Mag Cons Rise Set Mag Cons Rise Set
SUN -26.7 Ari 7.05am 5.29pm -26.7 Tau 7.33am 5.03pm
Merc -1.1 Ari 8.18am 6.00pm 2.9 Tau 8.46am 5.59pm
Venus -3.9 Ari 7.52am 5.56pm -3.8 Tau 8.59am 6.05pm
Mars 1.6 Gem 11.33am 8.34pm 1.7 Gem 10.46am 8.04pm
Jupiter -2.2 Aqr 12.54am 2.34pm -2.4 Aqr 11.12pm 12.45pm
Saturn 0.7 Cap 11.35pm 1.52pm 0.6 Cap 9.39pm 11.56am
Uranus 5.9 Ari 7.06am 5.29pm 5.9 Ari 5.13am 3.32pm
Neptune 7.9 Aqr 2.56am 3.33pm 7.9 Aqr 1.01am 1.36pm
Pluto 14.5 Sgr 10.09pm 1.06pm 14.5 Sgr 8.09pm 11.08am
May 1 NZST May 31 NZST
Twilights morning evening morning evening
Civil: start 6.39am, end 5.56pm start 7.05am, end 5.31pm
Nautical: start 6.06am, end 6.29pm start 6.31am, end 6.06pm
Astro: start 5.34am, end 7.01pm start 5.58am, end 6.39pm
MAY PHASES OF THE MOON, times NZST & UT
Last quarter: May 4 at 7.50am (May 6, 19:50 UT)
New Moon: May 12 at 7.00am (May 11,19:00 UT)
First quarter: May 20 at 7.13am (May 19, 19:13 UT)
Full Moon: May 26 at 11.14pm (11:14 UT)
A brief total eclipse of the moon takes place late evening of May 26. The eclipse is total from 11:11:58 pm to 11:26:47 pm, a duration of just under 15 minutes. Greatest eclipse is at 11:18:43 when the northern, lower edge of the moon will be only just inside the umbra. Hence this edge of the moon is likely to be brightest. The eclipse is partial from 9:44:44 pm to 12:52:49. All stages of the eclipse are visible from New Zealand and eastern Australia with totality visible from all parts of the continent.
THE PLANETS in MAY
MERCURY and VENUS move in tandem to the east through the stars during April. They are quite close to one another and to the Sun all month, as a result observation will be difficult.
At first Mercury draws ahead of Venus reaching its greatest elongation 22° east of the Sun on the 17th. The planet then slows until it is stationary on the 30th. This enables Venus to overtake Mercury, the two being 0.4° on the 29th.
By the end of May, the planets set about an hour after the Sun. Half an hour after sunset Venus will be just over 4° above the horizon, Mercury slightly less.
MARS continues to set about 3 hours after the Sun all month. The crescent moon will be just over 2° below the planet on May 16, best seen about 6pm. Both Mars and the moon are north of the ecliptic so will be fairly low in New Zealand skies.
JUPITER and SATURN are still best observed in the morning sky, although both rise before midnight by the 31st. The moon is some 3.5° from Saturn on the morning of May 4 and again on the 31st. It is 4.5° from Jupiter in the morning of May 5.
Jupiter's equator is close to edge on as seen from the Earth. As a result a series of mutual events of the Jovian satellites is occurring. Many are visible from New Zealand. Predictions can be found using Dave Herald's Occult program.
URANUS becomes a morning object following its end of April conjunction with the Sun. By the end of May it rises two hours before the Sun, so will be observable before the sky brightens.
NEPTUNE moves further up into the morning sky.
PLUTO Rises during the evening in May, now about an hour and a half before Saturn.
POSSIBLE BINOCULAR ASTEROIDS in May
May 1 NZST May 30 NZST
Mag Cons transit Mag Cons transit
(1) Ceres 9.1 Psc 11.31am 9.2 Cet 10.17am
(4) Vesta 7.0 Leo 8.33pm 7.0 Leo 6.54pm
CERES rise at 5.42am on the 1st and 4.42am on the 31st, so becomes visible in the morning sky. It moves from Pisces to Cetus on May 13.
VESTA sets at 1.33am on May 1 and at 12.07am on the 31st. Thus it is visible in the evening sky.
-- Brian Loader
4. Variable Star News
Novae Announcements
There have been two nova announcements in the VSS Google Discussion Group. The first was a posting by Mark Blackford advising a discovery in Sagittarius on ASAS-SN: 2021 Mar. 25.29 UT by the All-Sky Automated Survey for Supernovae. Full information was provided in AAVSO Alert Notice 736 (March 2021). Discovery magnitude 11.9 and the allocated designation was 6594 Sgr (= N Sgr 2021).
The second was by VSS member Andrew Pearce from his site in Nedlands, Western Australia. Andrew caught this event on his Canon 1100 digital SLR camera (+ 100-mm-f.l. f/2.8 lens) on April 4.825 UT at magnitude 8.4, remarkably bright considering the number of supernova watches now being conducted. The approximate position of the variable was found to be R.A. = 17h58m16s.7, Decl. = -29d14'49" (equinox J2000.0).
The full official announcement V6595 SAGITTARII = NOVA SAGITTARII 2021 No. 2 = PNV J17581670-2914490 is available here URL: http://www.cbat.eps.harvard.edu/index.html
E. Kazarovets has informed the Central Bureau that this nova has received the permanent GCVS designation V6595 Sgr.
Spectroscopy has now been undertaken on both these outbursts and they are both classical iron type nova.
PS: AAVSO Alert Notice 740 announced another nova, this time in Scorpio (V1710 Sco). Congratulations to Paul Camilleri in Katherine, NT. who discovered the nova independently some hours after the All-Sky Automated Survey for Supernovae (ASAS-SN) imaged it. (From Mark Blackford, email 15 April 2021).
VSS Newsletters
The second issue for the year of the Variable Stars South Newsletter will be published before the end of April. Visit the website towards the end of the month to see the latest issue; previous issues are also available there. www.vatiablestarssouth.org
Exoplanet Transit Study
Carl Knight at his observatory in the Manawatu observes transits of stars by planets called exoplanets. This is a developing field for astronomers, and his current project is in association with Pulkonov Observatory, St Petersburg observing unusual exoplanets such as WASP 17b. This planet is estimated to be 0.486 x the mass of Jupiter and it was the first planet discovered to have a retrograde orbit, meaning it orbits in a direction counter to the rotation of its host star. WASP stands for a collaborative program of Wide Angle Searches for Planets.
Carl writes: Exoplanet transit work requires capturing a signal in the order of what is acceptable noise (1-2 hundredths of a magnitude) elsewhere. My aim is, as much as possible, in addition to all the usual practices of dark subtraction and flat fielding, to keep the centroid of a star on the same pixels on the camera throughout a transit. This is to avoid any residual difference in pixel sensitivity to wavelength after flat fielding.
Where exoplanet work differs from traditional photometry is that the light curve captured is all about capturing the contact points (i.e. the start and end contacts of the leading and trailing edges of the exoplanet disc across the surface of the parent star) and the mid-point of the transit. Rigorously derived magnitudes in filters B,V,R or I don't matter nearly as much as capturing the relative dimming of a star caused by a transit.
To that end I use MPOSoft Connections to do image capture, plate solving, etc. and PHD Guiding via a second camera on an off axis guider ahead of any filters to guide the mount. As my day job is computer programmer, I wrote my own ASCOM driver to get the best performance out of my Meade 12" LX90 SCT. It is a polar aligned fork mount. Whilst the fork limits the travel of equipment in the declination axis, and therefore means I cannot observe closer to the celestial pole than 72 degrees south, it requires no meridian flip and therefore no break in continuous observations.
There is a balance to be struck between cadence of observations (time resolution) and signal to noise ratio (magnitude resolution). I aim for no longer than 30s exposures with a blue blocking filter. The limiting magnitude of this arrangement turns out to be close to magnitude 15. The dimmest target I have captured a transit from is about that magnitude. The blue blocking filter effectively covers the standard wavelengths of V and R through to I. By removing the B band, the greater extinction of the B band as the observing altitude drops below the traditional cut off of around 30 degrees altitude is minimised, and a flatter light curve results. It is not at all unusual for transit observations to continue below 30 degrees altitude. As long as the contact points, etc. remain identifiable and the distortion of the light curve can be compensated for/corrected a useful light curve can be obtained.
WASP-17b is a target of special interest because the time of transit has either drifted from when expected, or the ephemeris is very wrong, most likely the latter. My most recent transit suggests it is in the order of 1.3 hours later than calculated. I report my transits to the EXPANSION project -- Exoplanetary trANsit Search with an Inter. Observational Network -- run from Pulkovo Observatory, St. Petersburg, Russia. As yet we have not published any discovery/correction paper to the existing ephemeris. We are still determining how the transit times differ from calculated over time – i.e. continuous, indicating a constantly changing orbit or simply a different but regular period. If continually changing, then WASP-17b is slowly spiralling further and further away from the host star and this may indicate a planet slowly escaping the WASP-17 system.
-- Items submitted by Alan Baldwin. 5. New Zealand Astrophotography Competition
The 2021 New Zealand Astrophotography Competition is now open for entries.
This year's competition will be judged by Robert Gendler, Robert is arguably one of the top deep sky astrophotographers in the world, he specializes in images of deep sky objects with very long exposure times.
For more information on our judge please take a look at his work on his website at http://www.robgendlerastropics.com/
The competition has three main categories deep sky, nightscape and solar system, last year we introduced a new time-lapse category but this year we have decided to tweak the rules of this new category so make sure you read over the rules and conditions of entry before submitting your entries. See below.
As in previous years the competition is sponsored by the Australian Sky & Telescope magazine, with a free 12 month subscription to their fine magazine to the winners of the nightscape and deep sky categories, as well as having their images printed in the magazine.
We are also lucky to be sponsored by Celestron Australia who are providing a $500 Celestron Australia Voucher to be spent on the Celestron Australia Website for the winner of the Deep Sky Category.
And sponsorship from Sky-Watcher Australia who are sponsoring the overall winner of the competition with a $500 NZD Sky-Watcher Australia Voucher to be spent on the Sky-Watcher Australia Website.
Astronz are sponsoring the Solar System category with a $300 Astronz gift voucher, Astronz is easily New Zealand's best known and most trusted supplier of Astronomical equipment.
The Auckland Astronomical Society will also provide a cash prize for each category winner.
The competition cutoff date is the 21st of September and the competition awards will be announced at the annual Burbidge dinner which is the Auckland Astronomical Society's premier annual event, keep an eye out on the society website for details on the forthcoming Burbidge dinner.
Conditions of entry and entry forms can be downloaded from the Auckland Astronomical Society website here at https://www.astronomy.org.nz/announcing-the-2021-new-zealand-astrophotography-competion-for-the-harry-williams-trophy/ "
-- From Jonathan Green, Director of the RASNZ Astrophotography Section, for the Auckland Astronomical Society.
6. Aotearoa Astrotourism Academy -- September 10-12
John Hearnshaw and Nalayini Davies announce the launch of a new enterprise, Aotearoa Astrotourism Academy, AAA.
The primary goal of AAA is to offer educational courses for current or aspiring astro-tourism night-sky guides, or for anyone interested in navigating the dark night sky.
We have assembled a small team of dedicated and expert instructors, and the plan is to offer a custom-tailored course over two and a half days (from 3:00 pm Friday afternoon to 4:45 pm Sunday afternoon) on all aspects of night-sky guiding. We hope to impart some of the basic skills and knowledge considered essential for those working in the fast growing astro-tourism industry.
The inaugural course will be in Lake Tekapo village from Friday 10 September 2021 to Sunday 12 September 2021. The venue will be the Godley Hotel, SH8, Lake Tekapo. This will be an intensive course comprising lectures, practical sessions (weather permitting for evening observing) and plenty of interactions between instructors and participants.
The content of the course will be as follows:
• Overview of dark sky places and astro-tourism in New Zealand -- Nalayini Davies
• Astro-tour stargazing (weather permitting) -- Gareth Davies and Alan Gilmore
• Coordinates and time in astronomy -- John Hearnshaw
• Our place in the Universe -- Nalayini Davies
• Principal objects to look at for astro-tourists -- Alan Gilmore
• How binoculars and telescopes work and how to use a telescope -- John Drummond
• Deep field astro-photography -- John Drummond
• Naming of stars and celestial objects -- John Hearnshaw
• Wide field astro-photography and time-lapse videos -- Fraser Gunn
• Notes for astro-tour guides -- Alan Gilmore
• Useful books, publications and apps for night sky guides -- John Hearnshaw and Nalayini Davies
Further details of the Academy and the course offered by AAA are to be found on the website www.aaanz.org. The website should be live very soon during April. We plan to include a guided visit to Mt John Observatory on the Friday afternoon.
Registrations can be made on-line at the website above. The registration fee of $500 covers participation in the course as well as morning and afternoon teas/coffees and lunch on the Saturday and Sunday. It is anticipated that participation will be limited to about 24.
For enquiries please email john.hearnshaw@canterbury.ac.nz or nbrito@vinstar.co.nz
7. Black Hole's Magnetic Field Imaged
The Event Horizon Telescope (EHT) collaboration, who produced the first ever image of a black hole, has revealed a new view of the massive object at the centre of the Messier 87 (M87) galaxy: how it looks in polarised light. This is the first time astronomers have been able to measure polarisation, a signature of magnetic fields, this close to the edge of a black hole. The observations are key to explaining how the M87 galaxy, located 55 million light-years away, is able to launch energetic jets from its core.
On 10 April 2019, scientists released the first ever image of a black hole, revealing a bright ring-like structure with a dark central region — the black hole’s shadow. Since then, the EHT collaboration has delved deeper into the data on the supermassive object at the heart of the M87 galaxy collected in 2017. They have discovered that a significant fraction of the light around the M87 black hole is polarised.
Light becomes polarised when it goes through certain filters, like the lenses of polarised sunglasses, or when it is emitted in hot regions of space where magnetic fields are present. In the same way that polarised sunglasses help us see better by reducing reflections and glare from bright surfaces, astronomers can sharpen their view of the region around the black hole by looking at how the light originating from it is polarised. Specifically, polarisation allows astronomers to map the magnetic field lines present at the inner edge of the black hole.
The bright jets of energy and matter that emerge from M87’s core and extend at least 5000 light-years from its centre are one of the galaxy’s most mysterious and energetic features. Most matter lying close to the edge of a black hole falls in. However, some of the surrounding particles escape moments before capture and are blown far out into space in the form of jets.
Astronomers have relied on different models of how matter behaves near the black hole to better understand this process. But they still don’t know exactly how jets larger than the galaxy are launched from its central region, which is comparable in size to the Solar System, nor how exactly matter falls into the black hole. With the new EHT image of the black hole and its shadow in polarised light, astronomers managed for the first time to look into the region just outside the black hole where this interplay between matter flowing in and being ejected out is happening.
The observations provide new information about the structure of the magnetic fields just outside the black hole. The team found that only theoretical models featuring strongly magnetised gas can explain what they are seeing at the event horizon.
“The observations suggest that the magnetic fields at the black hole’s edge are strong enough to push back on the hot gas and help it resist gravity’s pull. Only the gas that slips through the field can spiral inwards to the event horizon,” explains Jason Dexter, Assistant Professor at the University of Colorado Boulder, US, and Coordinator of the EHT Theory Working Group.
To observe the heart of the M87 galaxy, the collaboration linked eight telescopes around the world to create a virtual Earth-sized telescope, the EHT. The impressive resolution obtained with the EHT is equivalent to that needed to measure the length of a credit card on the surface of the Moon.
The EHT setup allowed the team to directly observe the black hole shadow and the ring of light around it, with the new polarised-light image clearly showing that the ring is magnetised. The results were published on March 24 in two separate papers in The Astrophysical Journal Letters by the EHT collaboration. The research involved over 300 researchers from multiple organisations and universities worldwide.
"The EHT is making rapid advancements, with technological upgrades being done to the network and new observatories being added. We expect future EHT observations to reveal more accurately the magnetic field structure around the black hole and to tell us more about the physics of the hot gas in this region," concludes EHT collaboration member Jongho Park, an East Asian Core Observatories Association Fellow at the Academia Sinica Institute of Astronomy and Astrophysics in Taipei.
For more information and graphics see
https://www.eso.org/public/news/eso2105/
-- Thanks to Karen Pollard for passing along the press release.
8. Star Formation Puzzle
Stars aren’t shy about announcing their births. As they are born from the collapse of giant clouds of hydrogen gas and begin to grow, they launch hurricane-like winds and spinning, lawn-sprinkler-style jets shooting off in opposite directions. During this phase, lasting only about 500,000 years, the star quickly bulks up on mass.
This action carves out huge cavities in the giant gas clouds. Astronomers thought these stellar temper tantrums would eventually clear out the surrounding gas cloud, halting the star’s growth. But in a comprehensive analysis of 304 fledgling stars in the Orion Complex, the nearest major star-forming region to Earth, researchers discovered that gas-clearing by a star’s outflow may not be as important in determining its final mass as conventional theories suggest. Their study was based on previously collected data from NASA’s Hubble and Spitzer space telescopes and the European Space Agency’s Herschel Space Telescope.
The study leaves astronomers still wondering why star formation is so inefficient. Only 30% of a hydrogen gas cloud’s initial mass winds up as a new-born star.
Though our galaxy is an immense city of at least 200 billion stars, the details of how they formed remain largely cloaked in mystery.
Scientists know that stars form from the collapse of huge hydrogen clouds that are squeezed under gravity to the point where nuclear fusion ignites. But only about 30 percent of the cloud’s initial mass winds up as a new-born star. Where does the rest of the hydrogen go during such a terribly inefficient process?
It has been assumed that a newly forming star blows off a lot of hot gas through light-sabre-shaped outflowing jets and hurricane-like winds launched from the encircling disk by powerful magnetic fields. These fireworks should squelch further growth of the central star. But a new, comprehensive Hubble survey shows that this most common explanation doesn’t seem to work, leaving astronomers puzzled.
Researchers used data previously collected from NASA’s Hubble and Spitzer space telescopes and the European Space Agency’s Herschel Space Telescope to analyse 304 developing stars, called protostars, in the Orion Complex, the nearest major star-forming region to Earth. (Spitzer and Herschel are no longer operational.) They then analysed how young stars’ powerful outflows carved out cavities in the vast gas clouds. The study is the largest-ever survey of developing stars.
From the survey they found that gas-clearing by a star’s outflow may not be as important in determining its final mass as conventional theories suggest. The researchers’ goal was to determine whether stellar outflows halt the infall of gas onto a star and stop it from growing. Instead, they found that the cavities in the surrounding gas cloud, sculpted by a forming star’s outflow, did not grow regularly as they matured, as theories propose.
“In one stellar formation model, if you start out with a small cavity, as the protostar rapidly becomes more evolved, its outflow creates an ever-larger cavity until the surrounding gas is eventually blown away, leaving an isolated star,” explained lead researcher Nolan Habel of the University of Toledo in Ohio. “Our observations indicate there is no progressive growth that we can find, so the cavities are not growing until they push out all of the mass in the cloud. So, there must be some other process going on that gets rid of the gas that doesn’t end up in the star.”
“We find that at the end of the protostellar phase, where most of the gas has fallen from the surrounding cloud onto the star, a number of young stars still have fairly narrow cavities,” said team member Tom Megeath of the University of Toledo. “So, this picture that is still commonly held of what determines the mass of a star and what halts the infall of gas is that this growing outflow cavity scoops up all of the gas. This has been pretty fundamental to our idea of how star formation proceeds, but it just doesn’t seem to fit the data here.”
Future telescopes such as NASA’s upcoming James Webb Space Telescope will probe deeper into a protostar’s formation process. Webb spectroscopic observations will observe the inner regions of disks surrounding protostars in infrared light, looking for jets in the youngest sources. Webb also will help astronomers measure the accretion rate of material from the disk onto the star, and study how the inner disk is interacting with the outflow.
Abridged from the article, with graphics, is at
https://scitechdaily.com/astronomers-puzzled-after-hubble-view-of-torrential-outflows-from-infant-stars-blows-hole-in-current-theories/
-- Thanks to John Bird for pointing this out.
9. Pristine Comet Borisov
New observations with the European Southern Observatory’s Very Large Telescope (ESO’s VLT) indicate that the interstellar comet 2I/Borisov is one of the most pristine ever observed. Astronomers suspect that the comet most likely never passed close to a star, making it an undisturbed relic of the cloud of gas and dust it formed from. Comet Borisov is only the second detected interstellar visitor to our Solar System.
2I/Borisov was discovered by amateur astronomer Gennady Borisov in August 2019 and was confirmed to have come from beyond the Solar System a few weeks later. “2I/Borisov could represent the first truly pristine comet ever observed,” says Stefano Bagnulo of the Armagh Observatory and Planetarium, Northern Ireland, UK, who led the new study published on March 30 in Nature Communications. The team believes that the comet had never passed close to any star before it flew by the Sun in 2019.
Bagnulo and his colleagues used the FORS2 instrument on ESO's VLT, located in northern Chile, to study 2I/Borisov in detail using a technique called polarimetry. Since this technique is regularly used to study comets and other small bodies of our Solar System, this allowed the team to compare the interstellar visitor with our local comets.
The team found that 2I/Borisov has polarimetric properties distinct from those of Solar System comets, with the exception of Hale–Bopp. Comet Hale–Bopp received much public interest in the late 1990s as a result of being easily visible to the naked eye. It was also one of the most pristine comets astronomers had ever seen. Prior to its most recent passage, Hale–Bopp is thought to have passed by our Sun only once. It had therefore barely been affected by solar wind and radiation. This means it was pristine, having a composition very similar to that of the cloud of gas and dust that formed the Solar System some 4.5 billion years ago.
By analysing the polarisation together with the colour of the comet the team concluded that 2I/Borisov is in fact even more pristine than Hale–Bopp. This means it carries untarnished signatures of the cloud of gas and dust it formed from.
“The fact that the two comets are remarkably similar suggests that the environment in which 2I/Borisov originated is not so different in composition from the environment in the early Solar System,” says Alberto Cellino, a co-author of the study, from the Astrophysical Observatory of Torino, National Institute for Astrophysics (INAF), Italy.
“The arrival of 2I/Borisov from interstellar space represented the first opportunity to study the composition of a comet from another planetary system and check if the material that comes from this comet is somehow different from our native variety,” explains Ludmilla Kolokolova, of the University of Maryland in the US, who was involved in the Nature Communications research.
Bagnulo hopes astronomers will have another, even better, opportunity to study an interstellar comet in detail before the end of the decade. “ESA is planning to launch Comet Interceptor in 2029, which will have the capability of reaching another visiting interstellar object, if one on a suitable trajectory is discovered,” he says, referring to an upcoming mission by the European Space Agency.
Even without a space mission, astronomers can use Earth’s many telescopes to gain insight into the different properties of rogue comets like 2I/Borisov. “Imagine how lucky we were that a comet from a system light-years away simply took a trip to our doorstep by chance,” says Bin Yang, an astronomer at ESO in Chile, who also took advantage of 2I/Borisov’s passage through our Solar System to study this mysterious comet. Her team’s results are published in Nature Astronomy.
Yang and her team used data from the Atacama Large Millimeter/ submillimeter Array (ALMA), in which ESO is a partner, as well as from ESO’s VLT, to study 2I/Borisov’s dust grains to gather clues about the comet’s birth and conditions in its home system.
They discovered that 2I/Borisov’s coma — an envelope of dust surrounding the main body of the comet — contains compact pebbles, grains about one millimetre in size or larger. In addition, they found that the relative amounts of carbon monoxide and water in the comet changed drastically as it neared the Sun. The team, which also includes Olivier Hainaut, says this indicates that the comet is made up of materials that formed in different places in its planetary system.
The observations by Yang and her team suggest that matter in 2I/Borisov’s planetary home was mixed from near its star to further out, perhaps because of the existence of giant planets, whose strong gravity stirs material in the system. Astronomers believe that a similar process occurred early in the life of our Solar System.
While 2I/Borisov was the first interstellar comet to pass by the Sun, it was not the first interstellar visitor. The first interstellar object to have been observed passing by our Solar System was 1I/'Oumuamua, another object studied with ESO’s VLT back in 2017. Originally classified as a comet, 'Oumuamua was later reclassified as an asteroid as it lacked a coma.
See the original press release at https://www.eso.org/public/news/eso2106/
-- Thanks to Karen Pollard for passing it along.
10. 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 2021 year starts at $40 for an ordinary
member, which includes an electronic subscription to our journal
'Southern Stars'.
11. Quote
"All new science happens at the limit of resolution: it is about seeing and understanding what has never been seen or understood before. But discoveries do not come from nothing, nor do they manifest themselves all at once in their entirety." -- Hugh Aldersey-Williams in 'Dutch Light - Christiaan Huygens and the Making of Science in Europe'.
Alan Gilmore Phone: 03 680 6817
P.O. Box 57 alan.gilmore@canterbury.ac.nz
Lake Tekapo 7945
New Zealand
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December Celestial Calendar by Dave Mitsky
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Minor Planet Occultation Updates:
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The above post/email/update represents my own words, views, research and opinions, unless stated otherwise the above work
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