RASNZ_20_08_2019
Royal Astronomical Society of New Zealand
eNewsletter: No. 224, 20 August 2019 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. Name ExoWorld Competition
2. Stargazers Getaway August 30 - September 1
3. The Solar System in September
4. 2019 AAS Astrophotography Competition
5. RASNZ Beatrice Hill-Tinsley Lecture Series
6. New Zealand Starlight Conference
7. Variable Star News
8. Secretary for National Astronomical Society
9. AstroQuest Citizen Science
10. 2020 Conference and RASNZ Centenary
11. Search for Nearby Earth-like Planets
12. Hubble Constant from Merging Neutron Stars
13. Relativity Tested Near Milky Way's Black Hole
14. How to Join the RASNZ
15. Kingdon-Tomlinson Fund
16. Gifford-Eiby Lecture Fund
17. Quote
1. Name ExoWorld Competition
Within the framework of its 100th anniversary commemorations, the International Astronomical Union (IAU) is organising the IAU100 NameExoWorlds global competition that allows any country in the world to give a popular name to a selected exoplanet and its host star. Over 70 countries have already signed up to organise national campaigns that will provide the public with an opportunity to vote. The aim of this initiative is to create awareness of our place in the Universe and to reflect on how the Earth would potentially be perceived by a civilisation on another planet.
NZ has been allocated the following star and its companion to name:
Star:
Identification: HD 137388
Type: Orange Dwarf, G-type
Constellation: Apus
Planet:
Identification: HD 137388b
Mass: 0.2 Jupiters
Orbital period: 330 Days
Discovery: 2011
Detection Method: Radial Velocity
Eccentricity: 0.36
The competition for NZ will go live on 1/09/19. Submissions for the designation of HD137388 and HD137388b will end on 30/09/19 5:00pm NZST.
Name ExoWorlds website: http://nameexoworlds.iau.org/
IAU100 website: https://www.iau-100.org/
NZ Competition website: https://space.auckland.ac.nz/nameexoworlds/
Please send queries to education@rasnz.org.nz
-- Carolle Varughese, RASNZ Education Group Leader
2. Stargazers Getaway August 30 - September 1
The North Otago Astronomical Society Inc, would like to invite you to Stargazers Getaway 2019, over the weekend of, Friday August 30th to Sunday September 1st at Camp Iona in Herbert.
This is the second year back for our iconic Stargazers Getaway, building on last year's camp, the first in over 10 years!
With expressions for attendees already coming in, this year is promising to be bigger and better!!
Children under 5 are free
Students 5-17 - $20 p/night, $35 for both
Adults +18 - $35 p/night, $60 for both
Day visits for talks - $5 p/day
Interested people who would like to either attend, speak or present a poster paper are asked to email the Stargazers Getaway Co-ordinator, Damien McNamara, as numbers are limited at :- solaur.science@gmail.com
3. The Solar System in September
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.
The southern spring equinox is on September 23 at 7:51pm.
NZDT starts on Sunday 29 September, when 2 a.m. advances to 3 a.m.
THE SUN and PLANETS in SEPTEMBER, Rise & Set, Magnitude & Constellation
SEPTEMBER 1 NZST SEPTEMBER 30 NZDT
Mag Cons Rise Set Mag Cons Rise Set
SUN -26.7 Leo 6.44am 5.58pm -26.7 Vir 6.55am 7.27pm
Merc -1.8 Leo 6.46am 5.39pm -0.2 Vir 7.36am 9.03pm
Venus -3.9 Leo 7.04am 6.19pm -3.9 Vir 7.30am 8.28pm
Mars 1.7 Leo 6.52am 5.56pm .1.8 Vir 6.38am 6.36pm
Jup -2.2 Oph 11.06am 2.05am -2.0 Oph 10.23am 1.25am
Sat 0.3 Sgr 1.11pm 4.11am 0.5 Sgr 12.16pm 3.17am
Uran 5.7 Ari 10.38pm 9.13am 5.7 Ari 9.40pm 8.17am
Nep 7.8 Aqr 6.30pm 7.20am 7.8 Aqr 5.32pm 6.24am
Pluto 14.4 Sgr 1.41pm 4.39am 14.5 Sgr 12.45pm 3.45am
SEPTEMBER 1 NZST SEPTEMBER 30 NZDT
Twilights morning evening morning evening
Civil: start 6.19am, end 6.24pm start 6.30am, end 7.53pm
Nautical: start 5.47am, end 6.56pm start 5.58am, end 8.25pm
Astro: start 5.15am, end 7.28pm start 5.24am, end 8.59pm
SEPTEMBER MOON PHASES, times NZST (NZDT Sep 29) & UT
First quarter: Sep 6 at 3.10pm (03:10 UT)
Full Moon: Sep 14 at 4.33pm (04:33 UT)
Last quarter Sep 22 at 2.41pm (02:41 UT)
New Moon: Sep 29 at 7.27am (Sep 28, 18:27 UT)
PLANETS in SEPTEMBER
MERCURY, VENUS, MARS and the Sun are all in Leo at the beginning of the month. Mars is at conjunction with the Sun on the 2nd, at about 10pm. Mercury is at superior conjunction on the 4th at about 2pm. The Sun and all three planets rise and set within a few minutes of one another resulting in none of these planets being observable.
By the end of September all four are in Virgo. Mercury and Venus will be evening objects with Mercury setting nearly 100 minutes after the Sun while Venus sets an hour after it. On the 30th Mercury, magnitude -1.8, should be visible to the west for a few minutes after 8pm NZDT, at an altitude about 9°. Venus will be 6° directly below Mercury. The moon, a very thin crescent, will be a similar distance to the right of Mercury. The previous evening, Mercury will be just over 1 degree to the right of Spica.
JUPITER and SATURN are both well placed for evening viewing, although Jupiter will set about 1.30 am NZDT on the 30th.
This month's lunar occultation of Saturn is on the 8th. It is visible from north and west Australia but is a miss for all of New South Wales and Victoria as well as the southeast of both Queensland and South Australia. Two evenings earlier, the moon at first quarter will be just over 2.5° from Jupiter early evening.
PLUTO, like Saturn, is in Sagittarius, the two planets are just under 7° apart.
URANUS becomes a late evening object in September, but is still best viewed as a morning object.
NEPTUNE, is in Aquarius and is at opposition on the 10th.
POSSIBLE BINOCULAR ASTEROIDS in SEPTEMBER
SEPTEMBER 1 NZST SEPTEMBER 30 NZDT
Mag Cons transit Mag Cons transit
(1) Ceres 8.9 Sco 5.56pm 9.1 Oph 5.35pm
(4) Vesta 7.7 Tau 5.21am 7.3 Tau 4.34am
(9) Metis 10.0 Cet 4.10am 9.3 Cet 3.14am
(15) Eunomia 8.6 Aqr 10.41pm 9.1 Aqr. 9.35pm
(29) Amphitrite 9.8 Psc 3.15am 9.1 Psc 2.04am
CERES joins Jupiter in Ophiuchus on September 10. By the end of the month they are about 5° apart. The asteroid is less than 3° from Antares mid month.
VESTA is in the morning sky in Taurus. It is about 13° above the Pleiades as seen near 5 am. The asteroid is stationary on the 25th.
METIS and AMPHITRITE brighten from 10th to 9th magnitude during September, making them possible binocular objects.
EUNOMIA dims during the month following its August opposition.
-- Brian Loader
4. 2019 AAS Astrophotography Competition
Calling all Astrophotographers, it's that time of year again, time to get your entries in for the 2019 New Zealand Astrophotography competition.
This year we are super lucky to have the "Bad Astronomer" Phil Plait as judge for the competition. Phil is an American astronomer, sceptic, writer and popular science blogger. Phil is best known for debunking misconceptions in Astronomy but is also a well-known Astrophotography enthusiast. For more on Phil see the Auckland Astronomical Society's website.
Australian Sky & Telescope are sponsoring both the Deep Sky category and the Nightscape / Artistic category. The winners of these categories will receive a one year subscription to the magazine as well as having their images printed in it.
Astronz are sponsoring the Solar System category with a $300 Astronz gift voucher. The Auckland Astronomical Society will also provide a cash prize for each category winner.
Auckland's Stardome Observatory and Planetarium will print a selection of the entrants images for an astrophotography exhibition that will be displayed at Stardome after the competition awards are announced. The exhibition will then tour around New Zealand at various events and galleries.
The competition cut-off date is the September 30 and the competition awards will be announced at the Auckland Astronomical Society's annual Burbidge dinner. Keep an eye on the AAS website for details.
The competition rules and entry forms can be found on the homepage of the Auckland Astronomical Society website
https://www.astronomy.org.nz/new/public/default.aspx
-- Adapted from a note to the nzastronomers group by Jonathan Green.
5. RASNZ Beatrice Hill-Tinsley Lecture Series
The RASNZ Lecture Trust Inc. is pleased to announce the itinerary of the 2019 Beatrice Hill Tinsley Lecture series where Babak A. Tafreshi will be speaking at various NZ venues.
The lecture tour will take place in October. They are:
Thu 10 Oct – Auckland;
Fri 11 – Tauranga;
Sat 12 – Hamilton;
Mon 14 – Napier;
Tue 15 – Wellington;
Wed 16 – Nelson;
Fri 18 – Christchurch;
Mon 28 – Dunedin;
Wed 30 – Wanganui;
Thu 31 Oct – New Plymouth.
Note, Babek will be speaking at the NZ Starlight Conference and Festival (Sunday 20 – Fri 25 October - https://starlightconference.org/ )
For more information, see - https://www.rasnz.org.nz/rasnz/beatrice-hill-tinsley-lectures.
-- From Keeping in Touch #32, 6th May 2019.
6. New Zealand Starlight Conference
Planning for the New Zealand Starlight Conference continues to make good
progress. The conference will take place this year at Lake Tekapo and will discuss all aspects of dark skies protection, combatting light pollution, astro-tourism, astro-photography, lighting technology, the aesthetics of the starry night sky, the health and environmental issues of light pollution and much more. The dates will be 20 - 23 October 2019. The conference website is https://starlightconference.org.
We have confirmed ten outstanding keynote speakers, and details are (or soon will be) on the website. We currently (mid-August) have 60 registrations and hope to double the number in the coming weeks.
Many speakers have offered talks on a wide range of topics based on lighting technology, light pollution and its health and environmental impacts, stargazing and astro-tourism. This will therefore be a highly multidisciplinary conference.
A theme of the Starlight Conference is `towards the first dark-sky nation´. To this end we are encouraging people from New Zealand´s already accredited dark sky places, and representatives from all aspiring dark sky places (about a dozen of them) to participate in the conference. We plan to run a workshop with experts from the International Dark-Sky Association on how to become a dark sky place with IDA accreditation.
Our website is up and running and gives all information you will need to register for the NZ Starlight Conference 2019. Currently the early-bird registration fee is NZD260; after 31 August this will increase to NZD290. We therefore encourage everyone who is interested to register to do so before the end of August.
The NZ Starlight Conference has been registered as an official IAU100 event.
We hope to see you in Tekapo this October. Please let me know if you can come and present a paper. Speaking slots are nearly full. We have spaces for more poster papers.
-- John Hearnshaw Chair, Organizing Committee, NZ Starlight Conference
7. Variable Star News
An interesting star system – QZ Carinae.
QZ Carinae lies in the Eta Carinae nebula, an area of star formation and is a quadruple star system. The stars in the system are all massive and thus hot and luminous. One close pair (A) has a rotation period of 20.7 days and the other pair (B) 6.0 days. The two systems take 25 years to orbit each other. Star B is a close binary (beta Lyrae type star) with a period estimated to be 5.99857 days.
The variable star was discovered by Auckland astronomers in 1972 and the system has been studied on and off since then. QZ Carina is a current VSS research project being coordinated by Stan Walker, Mark Blackford and Ed Budding. More observations are required to update the eclipse elements and determine the orbital periods up to August 2019. Some further observations have been found in previous variable star observational records and more would b
This region of the sky is always of interest. A reminder that there is a special VSS campaign running from this year until the end of 2021 to gather frequent observations to monitor eta Carinae during its current phase of brightening. This was first mentioned in the RASNZ May newsletter. For further information on these projects refer to the VSS web-site (https://www.variablestarssouth.org/ ) and VSS Newsletters 2019 April and July.
Nova in Orion
A notice has been received from CBET advising a nova in Orion. “Shigehisa Fujikawa, Kan'onji, Kagawa, Japan, reports his discovery of an apparent nova (mag 9.4) on a CCD frame (limiting mag 13.5) taken on Aug 7.798 UT”. CBET notice (CBET 4659) published 2019 August 15. The nova appears to be a "very fast expanding" classical type-He/N nova from a spectroscopic observation at Cerro Pachon, Chile. The nova has been given the designation V2860 Orionis.
-- Alan Baldwin
8. Secretary for National Astronomical Society
The Royal New Zealand Astronomical Society (RASNZ) is seeking a suitable person to take on the voluntary role of Secretary. This is an important role within RASNZ. The new appointee will be a key member of RASNZ helping administer and make strategic decisions for RASNZ.
No formal qualifications or prior experience in a similar role are necessary, and, this role does not preclude holders of positions in other astronomical societies. However, knowledge of RASNZ rules
(https://www.rasnz.org.nz/images/articleFiles/Council/Rules2015.pdf), history and operations would be beneficial to performing the duties. Templates created by former holders of this position will be made available. This role can be undertaken entirely from the home office but attendance at the RASNZ Council's AGM held once a year at the RASNZ annual conference is strongly encouraged.
The responsibilities of the Secretary include:
(i) Receive and send physical and electronic correspondence on behalf of the RASNZ, document it and draw appropriate people's attention to the
correspondence;
(ii) Compile the Council's Annual Report and prepare it for approval by the Council in time for publication in the March issue of Southern Stars, and
(iii) Maintain a record of meetings and motions, both physical and electronic.
This offers a great opportunity for someone to contribute to the nationwide support and promotion of astronomy, science education and related research.
Contact: Nick Rattenbury (nicholas.rattenbury@gmail.com)
President - RASNZ
9. AstroQuest Citizen Science
AstroQuest are looking for volunteer astronomers to study crowded images of galaxies and work out which light is coming from which galaxy. All you need is a computer and the internet.
Organisation: International Centre for Radio Astronomy Research
https://www.icrar.org/outreach-education/outreach-initiatives/citizen-science/
-- From Royal Society of NZ Alert No. 1057, 25 July.
10. 2020 Conference and RASNZ Centenary
The 2020 Conference will be held 8-10 May at Wellington with the Wharewaka Function Centre the venue (near the Michael Fowler Centre) in downtown Wellington. The Wellington Astronomical Society is hosting this conference.
2020 marks a significant milestone in the life of the Society as it was founded in November 1920 with 75 members.
The SCC invites ideas from members how the Society might commemorate its centenary at next year’s conference. Please send your suggestions to the SCC at conference@rasnz.org.nz.
-- Glen Rowe, Chair, Standing Conference Committee
11. Search for Nearby Earth-like Planets
Newly-built planet-finding instrument installed on Very Large Telescope, Chile, begins 100-hour observation of nearby stars Alpha Centauri A and B, aiming to be first to directly image a habitable exoplanet
Breakthrough Watch, the global astronomical program looking for Earth-like planets around nearby stars, and the European Southern Observatory (ESO), Europe’s foremost intergovernmental astronomical organisation, today announced “first light” on a newly-built planet-finding instrument at ESO’s Very Large Telescope in the Atacama Desert, Chile.
The instrument, called NEAR (Near Earths in the AlphaCen Region), is designed to hunt for exoplanets in our neighbouring star system, Alpha Centauri, within the “habitable zones” of its two Sun-like stars, where water could potentially exist in liquid form. It has been developed over the last three years and was built in collaboration with the University of Uppsala in Sweden, the University of Liège in Belgium, the California Institute of Technology in the US, and Kampf Telescope Optics in Munich, Germany.
Since 23 May ESO’s astronomers at ESO’s Very Large Telescope (VLT) have been conducting a ten-day observing run to establish the presence or absence of one or more planets in the star system. Observations concluded on 11 June. Planets in the system (twice the size of Earth or bigger), would be detectable with the upgraded instrumentation. The near- to thermal-infrared range is significant as it corresponds to the heat emitted by a candidate planet, and so enables astronomers to determine whether the planet’s temperature allows liquid water.
Alpha Centauri is the closest star system to our Solar System, at 4.37 light-years (about 40 trillion km) away. It consists of two Sun-like stars, Alpha Centauri A and B, plus the red dwarf star, Proxima Centauri. Current knowledge of Alpha Centauri’s planetary systems is sparse. In 2016, a team using ESO instruments discovered one Earth-like planet orbiting Proxima Centauri. But Alpha Centauri A and B remain unknown quantities; it is not clear how stable such binary star systems are for Earth-like planets, and the most promising way to establish whether they exist around these nearby stars is to attempt to observe them.
Imaging such planets, however, is a major technical challenge, since the starlight that reflects off them is generally billions of times dimmer than the light coming to us directly from their host stars; resolving a small planet close to its star at a distance of several light-years has been compared to spotting a moth circling a street lamp dozens of miles away. To solve this problem, in 2016 Breakthrough Watch and ESO launched a collaboration to build a special instrument called a thermal infrared coronagraph, designed to block out most of the light coming from the star and optimised to capture the infrared light emitted by the warm surface of an orbiting planet, rather than the small amount of starlight it reflects. Just as objects near to the Sun (normally hidden by its glare) can be seen during a total eclipse, so the coronagraph creates a kind of artificial eclipse of its target star, blocking its light and allowing much dimmer objects in its vicinity to be detected. This marks a significant advance in observational capabilities.
The coronagraph has been installed on one of the VLT’s four 8-metre-aperture telescopes, upgrading and modifying an existing instrument, called VISIR, to optimise its sensitivity to infrared wavelengths associated with potentially habitable exoplanets. It will therefore be able to search for heat signatures similar to that of the Earth, which absorbs energy from the Sun and emits it in the thermal infrared wavelength range. NEAR modifies the existing VISIR instrument in three ways, combining several cutting-edge astronomical engineering achievements. First, it adapts the instrument for coronagraphy, enabling it to drastically reduce the light of the target star and thereby reveal the signatures of potential terrestrial planets. Second, it uses a technique called adaptive optics to strategically deform the telescope’s secondary mirror, compensating for the blur produced by the Earth’s atmosphere. Third, it employs novel chopping strategies that also reduce noise, as well as potentially allowing the instrument to switch rapidly between target stars -— as fast as every 100 milliseconds — maximising the available telescope time.
For details and images see
https://www.eso.org/public/news/eso1911/
-- From the above press release forwarded by Karen Pollard.
12. Hubble Constant from Merging Neutron Stars
Radio astronomers have demonstrated how a combination of gravitational-wave and radio observations, along with theoretical modelling, can turn the mergers of pairs of neutron stars into a “cosmic ruler” capable of measuring the expansion of the Universe and resolving an outstanding question over its rate.
The astronomers used the U.S. National Science Foundation’s Very Long Baseline Array (VLBA), the Karl G. Jansky Very Large Array (VLA) and the Robert C. Byrd Green Bank Telescope (GBT) to study the aftermath of the collision of two neutron stars that produced gravitational waves detected in 2017. This event offered a new way to measure the expansion rate of the Universe, known by scientists as the Hubble Constant. The expansion rate of the Universe can be used to determine its size and age, as well as serve as an essential tool for interpreting observations of objects elsewhere in the Universe.
Two leading methods of determining the Hubble Constant use the characteristics of the Cosmic Microwave Background, the leftover radiation from the Big Bang, or a specific type of supernova explosions, called Type Ia, in the distant Universe. However, these two methods give different results.
“The neutron star merger gives us a new way of measuring the Hubble Constant, and hopefully of resolving the problem,” said Kunal Mooley, of the National Radio Astronomy Observatory (NRAO) and Caltech.
The technique is similar to that using the supernova explosions. Type Ia supernova explosions are thought to all have an intrinsic brightness which can be calculated based on the speed at which they brighten and then fade away. Measuring the brightness as seen from Earth then tells the distance to the supernova explosion. Measuring the Doppler shift of the light from the supernova’s host galaxy indicates the speed at which the galaxy is receding from Earth. The speed divided by the distance yields the Hubble Constant. To get an accurate figure, many such measurements must be made at different distances.
When two massive neutron stars collide, they produce an explosion and a burst of gravitational waves. The shape of the gravitational-wave signal tells scientists how “bright” that burst of gravitational waves was. Measuring the “brightness,” or intensity of the gravitational waves as received at Earth can yield the distance.
“This is a completely independent means of measurement that we hope can clarify what the true value of the Hubble Constant is,” Mooley said.
However, there’s a twist. The intensity of the gravitational waves varies with their orientation with respect to the orbital plane of the two neutron stars. The gravitational waves are stronger in the direction perpendicular to the orbital plane, and weaker if the orbital plane is edge-on as seen from Earth.
“In order to use the gravitational waves to measure the distance, we needed to know that orientation,” said Adam Deller, of Swinburne University of Technology in Australia.
Over a period of months, the astronomers used the radio telescopes to measure the movement of a superfast jet of material ejected from the explosion. “We used these measurements along with detailed hydrodynamical simulations to determine the orientation angle, thus allowing use of the gravitational waves to determine the distance,” said Ehud Nakar from Tel Aviv University.
This single measurement, of an event some 130 million light-years from Earth, is not yet sufficient to resolve the uncertainty, the scientists said, but the technique now can be applied to future neutron-star mergers detected with gravitational waves.
“We think that 15 more such events that can be observed both with gravitational waves and in great detail with radio telescopes, may be able to solve the problem,” said Kenta Hotokezaka, of Princeton University. “This would be an important advance in our understanding of one of the most important aspects of the Universe,” he added.
The international scientific team led by Hotokezaka is reporting its results in the journal Nature Astronomy.
For text & graphics see: https://public.nrao.edu/news/new-method-measuring-universe-expansion/
-- From a U.S. National Radio Astronomy Observatory press release forwarded by Karen Pollard.
13. Relativity Tested Near Milky Way's Black Hole
More than 100 years after Albert Einstein published his iconic general theory of relativity, it is beginning to fray at the edges, said Andrea Ghez, UCLA professor of physics and astronomy. Now, in the most comprehensive test of general relativity near the monstrous black hole at the centre of our galaxy, Ghez and her research team report July 25 in the journal Science that Einstein’s general theory of relativity holds up.
“Einstein’s right, at least for now,” said Ghez, a co-lead author of the research. “We can absolutely rule out Newton’s law of gravity. Our observations are consistent with Einstein’s theory of general relativity. However, his theory is definitely showing vulnerability. It cannot fully explain gravity inside a black hole, and at some point we will need to move beyond Einstein’s theory to a more comprehensive theory of gravity that explains what a black hole is.”
Einstein’s 1915 general theory of relativity holds that what we perceive as the force of gravity arises from the curvature of space and time. The scientist proposed that objects such as the Sun and the Earth change this geometry. Einstein’s theory is the best description of how gravity works, said Ghez, whose UCLA-led team of astronomers has made direct measurements of the phenomenon near a supermassive black hole -- research Ghez describes as “extreme astrophysics.”
The laws of physics, including gravity, should be valid everywhere in the universe, said Ghez, who added that her research team is one of only two groups in the world to watch a star known as S0-2 make a complete orbit in three dimensions around the supermassive black hole at the centre of the Milky Way. The full orbit takes 16 years, and the black hole’s mass is about four million times that of the Sun.
The researchers say their work is the most detailed study ever conducted into the supermassive black hole and Einstein’s general theory of relativity.
The key data in the research were spectra that Ghez’s team analysed this April, May and September as her “favourite star” made its closest approach to the enormous black hole. Spectra offer important information about the star from which the light travels and show the composition of the star. This data was combined with measurements Ghez and her team have made over the last 24 years.
Spectra collected at the W. M. Keck Observatory in Hawaii provide the third dimension, revealing the star’s motion at a level of precision not previously attained. (Images of the star the researchers took at the Keck Observatory provide the two other dimensions.)
“What’s so special about S0-2 is we have its complete orbit in three dimensions,” said Ghez. “That’s what gives us the entry ticket into the tests of general relativity. We asked how gravity behaves near a supermassive black hole and whether Einstein’s theory is telling us the full story. Seeing stars go through their complete orbit provides the first opportunity to test fundamental physics using the motions of these stars.”
Ghez’s research team was able to see the co-mingling of space and time near the supermassive black hole. “In Newton’s version of gravity, space and time are separate, and do not co-mingle; under Einstein, they get completely co-mingled near a black hole,” she said.
The researchers studied photons as they travelled from S0-2 to Earth. S0-2 moves around the black hole at blistering speeds of more than 4,400 km/s at its closest approach. Einstein had reported that in this region close to the black hole, photons have to do extra work. Their wavelength as they leave the star depends not only on how fast the star is moving, but also on how much energy the photons expend to escape the black hole’s powerful gravitational field. Near a black hole, gravity is much stronger than on Earth.
This is the first of many tests of general relativity Ghez’s research team will conduct on stars near the supermassive black hole. Among the stars that most interest her is S0-102, which has the shortest orbit, taking 11.5 years to complete a full orbit around the black hole. Most of the stars Ghez studies have orbits of much longer than a human lifespan.
For the original text & graphics see:
http://newsroom.ucla.edu/releases/einstein-general-relativity-theory-questioned-ghez
-- From a University of California press release forwarded by Karen Pollard.
14. How to Join the RASNZ
RASNZ membership is open to all individuals with an interest in
astronomy in New Zealand. Information about the society and its
objects can be found at
http://rasnz.org.nz/rasnz/membership-benefits
A membership form can be either obtained from 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'.
15. Kingdon-Tomlinson Fund
The RASNZ is responsible for recommending to the trustees of the Kingdon Tomlinson Fund that grants be made for astronomical projects. The grants may be to any person or persons, or organisations, requiring funding for any projects or ventures that promote the progress of astronomy in New Zealand. Applications are now invited for grants from the Kingdon-Tomlinson Fund. The application should reach the Secretary by 1 November 2019 for consideration by Council. Full details are set down in the RASNZ By-Laws, Section J. For an application form contact the RASNZ Executive Secretary, secretary@rasnz.org.nz
16. 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.
For an application form contact the Executive Secretary
secretary@rasnz.org.nz,
17. Quote
"Flying fish landed on the deck, albatrosses and sperm whales were constant companions, and on 9 August [1841] a meteor was seen to burst on the south-western sky. It was a prelude to a shower of shooting stars that was expected in the middle of the month. [James Clark] Ross made sure he had instructed all the men on watch what to look out for. So zealously did they throw themselves into their task that one of the men was reluctant to be relieved of his post, saying he was sure two or three stars were about to fall, as 'he'd been watching them and could see they were shaking!'" -- Michael Palin's 'Erebus - The Story of a Ship', p.124.
Alan Gilmore Phone: 03 680 6817
P.O. Box 57 alan.gilmore@canterbury.ac.nz
Lake Tekapo 7945
New Zealand
eNewsletter: No. 224, 20 August 2019 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. Name ExoWorld Competition
2. Stargazers Getaway August 30 - September 1
3. The Solar System in September
4. 2019 AAS Astrophotography Competition
5. RASNZ Beatrice Hill-Tinsley Lecture Series
6. New Zealand Starlight Conference
7. Variable Star News
8. Secretary for National Astronomical Society
9. AstroQuest Citizen Science
10. 2020 Conference and RASNZ Centenary
11. Search for Nearby Earth-like Planets
12. Hubble Constant from Merging Neutron Stars
13. Relativity Tested Near Milky Way's Black Hole
14. How to Join the RASNZ
15. Kingdon-Tomlinson Fund
16. Gifford-Eiby Lecture Fund
17. Quote
1. Name ExoWorld Competition
Within the framework of its 100th anniversary commemorations, the International Astronomical Union (IAU) is organising the IAU100 NameExoWorlds global competition that allows any country in the world to give a popular name to a selected exoplanet and its host star. Over 70 countries have already signed up to organise national campaigns that will provide the public with an opportunity to vote. The aim of this initiative is to create awareness of our place in the Universe and to reflect on how the Earth would potentially be perceived by a civilisation on another planet.
NZ has been allocated the following star and its companion to name:
Star:
Identification: HD 137388
Type: Orange Dwarf, G-type
Constellation: Apus
Planet:
Identification: HD 137388b
Mass: 0.2 Jupiters
Orbital period: 330 Days
Discovery: 2011
Detection Method: Radial Velocity
Eccentricity: 0.36
The competition for NZ will go live on 1/09/19. Submissions for the designation of HD137388 and HD137388b will end on 30/09/19 5:00pm NZST.
Name ExoWorlds website: http://nameexoworlds.iau.org/
IAU100 website: https://www.iau-100.org/
NZ Competition website: https://space.auckland.ac.nz/nameexoworlds/
Please send queries to education@rasnz.org.nz
-- Carolle Varughese, RASNZ Education Group Leader
2. Stargazers Getaway August 30 - September 1
The North Otago Astronomical Society Inc, would like to invite you to Stargazers Getaway 2019, over the weekend of, Friday August 30th to Sunday September 1st at Camp Iona in Herbert.
This is the second year back for our iconic Stargazers Getaway, building on last year's camp, the first in over 10 years!
With expressions for attendees already coming in, this year is promising to be bigger and better!!
Children under 5 are free
Students 5-17 - $20 p/night, $35 for both
Adults +18 - $35 p/night, $60 for both
Day visits for talks - $5 p/day
Interested people who would like to either attend, speak or present a poster paper are asked to email the Stargazers Getaway Co-ordinator, Damien McNamara, as numbers are limited at :- solaur.science@gmail.com
3. The Solar System in September
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.
The southern spring equinox is on September 23 at 7:51pm.
NZDT starts on Sunday 29 September, when 2 a.m. advances to 3 a.m.
THE SUN and PLANETS in SEPTEMBER, Rise & Set, Magnitude & Constellation
SEPTEMBER 1 NZST SEPTEMBER 30 NZDT
Mag Cons Rise Set Mag Cons Rise Set
SUN -26.7 Leo 6.44am 5.58pm -26.7 Vir 6.55am 7.27pm
Merc -1.8 Leo 6.46am 5.39pm -0.2 Vir 7.36am 9.03pm
Venus -3.9 Leo 7.04am 6.19pm -3.9 Vir 7.30am 8.28pm
Mars 1.7 Leo 6.52am 5.56pm .1.8 Vir 6.38am 6.36pm
Jup -2.2 Oph 11.06am 2.05am -2.0 Oph 10.23am 1.25am
Sat 0.3 Sgr 1.11pm 4.11am 0.5 Sgr 12.16pm 3.17am
Uran 5.7 Ari 10.38pm 9.13am 5.7 Ari 9.40pm 8.17am
Nep 7.8 Aqr 6.30pm 7.20am 7.8 Aqr 5.32pm 6.24am
Pluto 14.4 Sgr 1.41pm 4.39am 14.5 Sgr 12.45pm 3.45am
SEPTEMBER 1 NZST SEPTEMBER 30 NZDT
Twilights morning evening morning evening
Civil: start 6.19am, end 6.24pm start 6.30am, end 7.53pm
Nautical: start 5.47am, end 6.56pm start 5.58am, end 8.25pm
Astro: start 5.15am, end 7.28pm start 5.24am, end 8.59pm
SEPTEMBER MOON PHASES, times NZST (NZDT Sep 29) & UT
First quarter: Sep 6 at 3.10pm (03:10 UT)
Full Moon: Sep 14 at 4.33pm (04:33 UT)
Last quarter Sep 22 at 2.41pm (02:41 UT)
New Moon: Sep 29 at 7.27am (Sep 28, 18:27 UT)
PLANETS in SEPTEMBER
MERCURY, VENUS, MARS and the Sun are all in Leo at the beginning of the month. Mars is at conjunction with the Sun on the 2nd, at about 10pm. Mercury is at superior conjunction on the 4th at about 2pm. The Sun and all three planets rise and set within a few minutes of one another resulting in none of these planets being observable.
By the end of September all four are in Virgo. Mercury and Venus will be evening objects with Mercury setting nearly 100 minutes after the Sun while Venus sets an hour after it. On the 30th Mercury, magnitude -1.8, should be visible to the west for a few minutes after 8pm NZDT, at an altitude about 9°. Venus will be 6° directly below Mercury. The moon, a very thin crescent, will be a similar distance to the right of Mercury. The previous evening, Mercury will be just over 1 degree to the right of Spica.
JUPITER and SATURN are both well placed for evening viewing, although Jupiter will set about 1.30 am NZDT on the 30th.
This month's lunar occultation of Saturn is on the 8th. It is visible from north and west Australia but is a miss for all of New South Wales and Victoria as well as the southeast of both Queensland and South Australia. Two evenings earlier, the moon at first quarter will be just over 2.5° from Jupiter early evening.
PLUTO, like Saturn, is in Sagittarius, the two planets are just under 7° apart.
URANUS becomes a late evening object in September, but is still best viewed as a morning object.
NEPTUNE, is in Aquarius and is at opposition on the 10th.
POSSIBLE BINOCULAR ASTEROIDS in SEPTEMBER
SEPTEMBER 1 NZST SEPTEMBER 30 NZDT
Mag Cons transit Mag Cons transit
(1) Ceres 8.9 Sco 5.56pm 9.1 Oph 5.35pm
(4) Vesta 7.7 Tau 5.21am 7.3 Tau 4.34am
(9) Metis 10.0 Cet 4.10am 9.3 Cet 3.14am
(15) Eunomia 8.6 Aqr 10.41pm 9.1 Aqr. 9.35pm
(29) Amphitrite 9.8 Psc 3.15am 9.1 Psc 2.04am
CERES joins Jupiter in Ophiuchus on September 10. By the end of the month they are about 5° apart. The asteroid is less than 3° from Antares mid month.
VESTA is in the morning sky in Taurus. It is about 13° above the Pleiades as seen near 5 am. The asteroid is stationary on the 25th.
METIS and AMPHITRITE brighten from 10th to 9th magnitude during September, making them possible binocular objects.
EUNOMIA dims during the month following its August opposition.
-- Brian Loader
4. 2019 AAS Astrophotography Competition
Calling all Astrophotographers, it's that time of year again, time to get your entries in for the 2019 New Zealand Astrophotography competition.
This year we are super lucky to have the "Bad Astronomer" Phil Plait as judge for the competition. Phil is an American astronomer, sceptic, writer and popular science blogger. Phil is best known for debunking misconceptions in Astronomy but is also a well-known Astrophotography enthusiast. For more on Phil see the Auckland Astronomical Society's website.
Australian Sky & Telescope are sponsoring both the Deep Sky category and the Nightscape / Artistic category. The winners of these categories will receive a one year subscription to the magazine as well as having their images printed in it.
Astronz are sponsoring the Solar System category with a $300 Astronz gift voucher. The Auckland Astronomical Society will also provide a cash prize for each category winner.
Auckland's Stardome Observatory and Planetarium will print a selection of the entrants images for an astrophotography exhibition that will be displayed at Stardome after the competition awards are announced. The exhibition will then tour around New Zealand at various events and galleries.
The competition cut-off date is the September 30 and the competition awards will be announced at the Auckland Astronomical Society's annual Burbidge dinner. Keep an eye on the AAS website for details.
The competition rules and entry forms can be found on the homepage of the Auckland Astronomical Society website
https://www.astronomy.org.nz/new/public/default.aspx
-- Adapted from a note to the nzastronomers group by Jonathan Green.
5. RASNZ Beatrice Hill-Tinsley Lecture Series
The RASNZ Lecture Trust Inc. is pleased to announce the itinerary of the 2019 Beatrice Hill Tinsley Lecture series where Babak A. Tafreshi will be speaking at various NZ venues.
The lecture tour will take place in October. They are:
Thu 10 Oct – Auckland;
Fri 11 – Tauranga;
Sat 12 – Hamilton;
Mon 14 – Napier;
Tue 15 – Wellington;
Wed 16 – Nelson;
Fri 18 – Christchurch;
Mon 28 – Dunedin;
Wed 30 – Wanganui;
Thu 31 Oct – New Plymouth.
Note, Babek will be speaking at the NZ Starlight Conference and Festival (Sunday 20 – Fri 25 October - https://starlightconference.org/ )
For more information, see - https://www.rasnz.org.nz/rasnz/beatrice-hill-tinsley-lectures.
-- From Keeping in Touch #32, 6th May 2019.
6. New Zealand Starlight Conference
Planning for the New Zealand Starlight Conference continues to make good
progress. The conference will take place this year at Lake Tekapo and will discuss all aspects of dark skies protection, combatting light pollution, astro-tourism, astro-photography, lighting technology, the aesthetics of the starry night sky, the health and environmental issues of light pollution and much more. The dates will be 20 - 23 October 2019. The conference website is https://starlightconference.org.
We have confirmed ten outstanding keynote speakers, and details are (or soon will be) on the website. We currently (mid-August) have 60 registrations and hope to double the number in the coming weeks.
Many speakers have offered talks on a wide range of topics based on lighting technology, light pollution and its health and environmental impacts, stargazing and astro-tourism. This will therefore be a highly multidisciplinary conference.
A theme of the Starlight Conference is `towards the first dark-sky nation´. To this end we are encouraging people from New Zealand´s already accredited dark sky places, and representatives from all aspiring dark sky places (about a dozen of them) to participate in the conference. We plan to run a workshop with experts from the International Dark-Sky Association on how to become a dark sky place with IDA accreditation.
Our website is up and running and gives all information you will need to register for the NZ Starlight Conference 2019. Currently the early-bird registration fee is NZD260; after 31 August this will increase to NZD290. We therefore encourage everyone who is interested to register to do so before the end of August.
The NZ Starlight Conference has been registered as an official IAU100 event.
We hope to see you in Tekapo this October. Please let me know if you can come and present a paper. Speaking slots are nearly full. We have spaces for more poster papers.
-- John Hearnshaw
7. Variable Star News
An interesting star system – QZ Carinae.
QZ Carinae lies in the Eta Carinae nebula, an area of star formation and is a quadruple star system. The stars in the system are all massive and thus hot and luminous. One close pair (A) has a rotation period of 20.7 days and the other pair (B) 6.0 days. The two systems take 25 years to orbit each other. Star B is a close binary (beta Lyrae type star) with a period estimated to be 5.99857 days.
The variable star was discovered by Auckland astronomers in 1972 and the system has been studied on and off since then. QZ Carina is a current VSS research project being coordinated by Stan Walker, Mark Blackford and Ed Budding. More observations are required to update the eclipse elements and determine the orbital periods up to August 2019. Some further observations have been found in previous variable star observational records and more would b
This region of the sky is always of interest. A reminder that there is a special VSS campaign running from this year until the end of 2021 to gather frequent observations to monitor eta Carinae during its current phase of brightening. This was first mentioned in the RASNZ May newsletter. For further information on these projects refer to the VSS web-site (https://www.variablestarssouth.org/ ) and VSS Newsletters 2019 April and July.
Nova in Orion
A notice has been received from CBET advising a nova in Orion. “Shigehisa Fujikawa, Kan'onji, Kagawa, Japan, reports his discovery of an apparent nova (mag 9.4) on a CCD frame (limiting mag 13.5) taken on Aug 7.798 UT”. CBET notice (CBET 4659) published 2019 August 15. The nova appears to be a "very fast expanding" classical type-He/N nova from a spectroscopic observation at Cerro Pachon, Chile. The nova has been given the designation V2860 Orionis.
-- Alan Baldwin
8. Secretary for National Astronomical Society
The Royal New Zealand Astronomical Society (RASNZ) is seeking a suitable person to take on the voluntary role of Secretary. This is an important role within RASNZ. The new appointee will be a key member of RASNZ helping administer and make strategic decisions for RASNZ.
No formal qualifications or prior experience in a similar role are necessary, and, this role does not preclude holders of positions in other astronomical societies. However, knowledge of RASNZ rules
(https://www.rasnz.org.nz/images/articleFiles/Council/Rules2015.pdf), history and operations would be beneficial to performing the duties. Templates created by former holders of this position will be made available. This role can be undertaken entirely from the home office but attendance at the RASNZ Council's AGM held once a year at the RASNZ annual conference is strongly encouraged.
The responsibilities of the Secretary include:
(i) Receive and send physical and electronic correspondence on behalf of the RASNZ, document it and draw appropriate people's attention to the
correspondence;
(ii) Compile the Council's Annual Report and prepare it for approval by the Council in time for publication in the March issue of Southern Stars, and
(iii) Maintain a record of meetings and motions, both physical and electronic.
This offers a great opportunity for someone to contribute to the nationwide support and promotion of astronomy, science education and related research.
Contact: Nick Rattenbury (nicholas.rattenbury@gmail.com)
President - RASNZ
9. AstroQuest Citizen Science
AstroQuest are looking for volunteer astronomers to study crowded images of galaxies and work out which light is coming from which galaxy. All you need is a computer and the internet.
Organisation: International Centre for Radio Astronomy Research
https://www.icrar.org/outreach-education/outreach-initiatives/citizen-science/
-- From Royal Society of NZ Alert No. 1057, 25 July.
10. 2020 Conference and RASNZ Centenary
The 2020 Conference will be held 8-10 May at Wellington with the Wharewaka Function Centre the venue (near the Michael Fowler Centre) in downtown Wellington. The Wellington Astronomical Society is hosting this conference.
2020 marks a significant milestone in the life of the Society as it was founded in November 1920 with 75 members.
The SCC invites ideas from members how the Society might commemorate its centenary at next year’s conference. Please send your suggestions to the SCC at conference@rasnz.org.nz.
-- Glen Rowe, Chair, Standing Conference Committee
11. Search for Nearby Earth-like Planets
Newly-built planet-finding instrument installed on Very Large Telescope, Chile, begins 100-hour observation of nearby stars Alpha Centauri A and B, aiming to be first to directly image a habitable exoplanet
Breakthrough Watch, the global astronomical program looking for Earth-like planets around nearby stars, and the European Southern Observatory (ESO), Europe’s foremost intergovernmental astronomical organisation, today announced “first light” on a newly-built planet-finding instrument at ESO’s Very Large Telescope in the Atacama Desert, Chile.
The instrument, called NEAR (Near Earths in the AlphaCen Region), is designed to hunt for exoplanets in our neighbouring star system, Alpha Centauri, within the “habitable zones” of its two Sun-like stars, where water could potentially exist in liquid form. It has been developed over the last three years and was built in collaboration with the University of Uppsala in Sweden, the University of Liège in Belgium, the California Institute of Technology in the US, and Kampf Telescope Optics in Munich, Germany.
Since 23 May ESO’s astronomers at ESO’s Very Large Telescope (VLT) have been conducting a ten-day observing run to establish the presence or absence of one or more planets in the star system. Observations concluded on 11 June. Planets in the system (twice the size of Earth or bigger), would be detectable with the upgraded instrumentation. The near- to thermal-infrared range is significant as it corresponds to the heat emitted by a candidate planet, and so enables astronomers to determine whether the planet’s temperature allows liquid water.
Alpha Centauri is the closest star system to our Solar System, at 4.37 light-years (about 40 trillion km) away. It consists of two Sun-like stars, Alpha Centauri A and B, plus the red dwarf star, Proxima Centauri. Current knowledge of Alpha Centauri’s planetary systems is sparse. In 2016, a team using ESO instruments discovered one Earth-like planet orbiting Proxima Centauri. But Alpha Centauri A and B remain unknown quantities; it is not clear how stable such binary star systems are for Earth-like planets, and the most promising way to establish whether they exist around these nearby stars is to attempt to observe them.
Imaging such planets, however, is a major technical challenge, since the starlight that reflects off them is generally billions of times dimmer than the light coming to us directly from their host stars; resolving a small planet close to its star at a distance of several light-years has been compared to spotting a moth circling a street lamp dozens of miles away. To solve this problem, in 2016 Breakthrough Watch and ESO launched a collaboration to build a special instrument called a thermal infrared coronagraph, designed to block out most of the light coming from the star and optimised to capture the infrared light emitted by the warm surface of an orbiting planet, rather than the small amount of starlight it reflects. Just as objects near to the Sun (normally hidden by its glare) can be seen during a total eclipse, so the coronagraph creates a kind of artificial eclipse of its target star, blocking its light and allowing much dimmer objects in its vicinity to be detected. This marks a significant advance in observational capabilities.
The coronagraph has been installed on one of the VLT’s four 8-metre-aperture telescopes, upgrading and modifying an existing instrument, called VISIR, to optimise its sensitivity to infrared wavelengths associated with potentially habitable exoplanets. It will therefore be able to search for heat signatures similar to that of the Earth, which absorbs energy from the Sun and emits it in the thermal infrared wavelength range. NEAR modifies the existing VISIR instrument in three ways, combining several cutting-edge astronomical engineering achievements. First, it adapts the instrument for coronagraphy, enabling it to drastically reduce the light of the target star and thereby reveal the signatures of potential terrestrial planets. Second, it uses a technique called adaptive optics to strategically deform the telescope’s secondary mirror, compensating for the blur produced by the Earth’s atmosphere. Third, it employs novel chopping strategies that also reduce noise, as well as potentially allowing the instrument to switch rapidly between target stars -— as fast as every 100 milliseconds — maximising the available telescope time.
For details and images see
https://www.eso.org/public/news/eso1911/
-- From the above press release forwarded by Karen Pollard.
12. Hubble Constant from Merging Neutron Stars
Radio astronomers have demonstrated how a combination of gravitational-wave and radio observations, along with theoretical modelling, can turn the mergers of pairs of neutron stars into a “cosmic ruler” capable of measuring the expansion of the Universe and resolving an outstanding question over its rate.
The astronomers used the U.S. National Science Foundation’s Very Long Baseline Array (VLBA), the Karl G. Jansky Very Large Array (VLA) and the Robert C. Byrd Green Bank Telescope (GBT) to study the aftermath of the collision of two neutron stars that produced gravitational waves detected in 2017. This event offered a new way to measure the expansion rate of the Universe, known by scientists as the Hubble Constant. The expansion rate of the Universe can be used to determine its size and age, as well as serve as an essential tool for interpreting observations of objects elsewhere in the Universe.
Two leading methods of determining the Hubble Constant use the characteristics of the Cosmic Microwave Background, the leftover radiation from the Big Bang, or a specific type of supernova explosions, called Type Ia, in the distant Universe. However, these two methods give different results.
“The neutron star merger gives us a new way of measuring the Hubble Constant, and hopefully of resolving the problem,” said Kunal Mooley, of the National Radio Astronomy Observatory (NRAO) and Caltech.
The technique is similar to that using the supernova explosions. Type Ia supernova explosions are thought to all have an intrinsic brightness which can be calculated based on the speed at which they brighten and then fade away. Measuring the brightness as seen from Earth then tells the distance to the supernova explosion. Measuring the Doppler shift of the light from the supernova’s host galaxy indicates the speed at which the galaxy is receding from Earth. The speed divided by the distance yields the Hubble Constant. To get an accurate figure, many such measurements must be made at different distances.
When two massive neutron stars collide, they produce an explosion and a burst of gravitational waves. The shape of the gravitational-wave signal tells scientists how “bright” that burst of gravitational waves was. Measuring the “brightness,” or intensity of the gravitational waves as received at Earth can yield the distance.
“This is a completely independent means of measurement that we hope can clarify what the true value of the Hubble Constant is,” Mooley said.
However, there’s a twist. The intensity of the gravitational waves varies with their orientation with respect to the orbital plane of the two neutron stars. The gravitational waves are stronger in the direction perpendicular to the orbital plane, and weaker if the orbital plane is edge-on as seen from Earth.
“In order to use the gravitational waves to measure the distance, we needed to know that orientation,” said Adam Deller, of Swinburne University of Technology in Australia.
Over a period of months, the astronomers used the radio telescopes to measure the movement of a superfast jet of material ejected from the explosion. “We used these measurements along with detailed hydrodynamical simulations to determine the orientation angle, thus allowing use of the gravitational waves to determine the distance,” said Ehud Nakar from Tel Aviv University.
This single measurement, of an event some 130 million light-years from Earth, is not yet sufficient to resolve the uncertainty, the scientists said, but the technique now can be applied to future neutron-star mergers detected with gravitational waves.
“We think that 15 more such events that can be observed both with gravitational waves and in great detail with radio telescopes, may be able to solve the problem,” said Kenta Hotokezaka, of Princeton University. “This would be an important advance in our understanding of one of the most important aspects of the Universe,” he added.
The international scientific team led by Hotokezaka is reporting its results in the journal Nature Astronomy.
For text & graphics see: https://public.nrao.edu/news/new-method-measuring-universe-expansion/
-- From a U.S. National Radio Astronomy Observatory press release forwarded by Karen Pollard.
13. Relativity Tested Near Milky Way's Black Hole
More than 100 years after Albert Einstein published his iconic general theory of relativity, it is beginning to fray at the edges, said Andrea Ghez, UCLA professor of physics and astronomy. Now, in the most comprehensive test of general relativity near the monstrous black hole at the centre of our galaxy, Ghez and her research team report July 25 in the journal Science that Einstein’s general theory of relativity holds up.
“Einstein’s right, at least for now,” said Ghez, a co-lead author of the research. “We can absolutely rule out Newton’s law of gravity. Our observations are consistent with Einstein’s theory of general relativity. However, his theory is definitely showing vulnerability. It cannot fully explain gravity inside a black hole, and at some point we will need to move beyond Einstein’s theory to a more comprehensive theory of gravity that explains what a black hole is.”
Einstein’s 1915 general theory of relativity holds that what we perceive as the force of gravity arises from the curvature of space and time. The scientist proposed that objects such as the Sun and the Earth change this geometry. Einstein’s theory is the best description of how gravity works, said Ghez, whose UCLA-led team of astronomers has made direct measurements of the phenomenon near a supermassive black hole -- research Ghez describes as “extreme astrophysics.”
The laws of physics, including gravity, should be valid everywhere in the universe, said Ghez, who added that her research team is one of only two groups in the world to watch a star known as S0-2 make a complete orbit in three dimensions around the supermassive black hole at the centre of the Milky Way. The full orbit takes 16 years, and the black hole’s mass is about four million times that of the Sun.
The researchers say their work is the most detailed study ever conducted into the supermassive black hole and Einstein’s general theory of relativity.
The key data in the research were spectra that Ghez’s team analysed this April, May and September as her “favourite star” made its closest approach to the enormous black hole. Spectra offer important information about the star from which the light travels and show the composition of the star. This data was combined with measurements Ghez and her team have made over the last 24 years.
Spectra collected at the W. M. Keck Observatory in Hawaii provide the third dimension, revealing the star’s motion at a level of precision not previously attained. (Images of the star the researchers took at the Keck Observatory provide the two other dimensions.)
“What’s so special about S0-2 is we have its complete orbit in three dimensions,” said Ghez. “That’s what gives us the entry ticket into the tests of general relativity. We asked how gravity behaves near a supermassive black hole and whether Einstein’s theory is telling us the full story. Seeing stars go through their complete orbit provides the first opportunity to test fundamental physics using the motions of these stars.”
Ghez’s research team was able to see the co-mingling of space and time near the supermassive black hole. “In Newton’s version of gravity, space and time are separate, and do not co-mingle; under Einstein, they get completely co-mingled near a black hole,” she said.
The researchers studied photons as they travelled from S0-2 to Earth. S0-2 moves around the black hole at blistering speeds of more than 4,400 km/s at its closest approach. Einstein had reported that in this region close to the black hole, photons have to do extra work. Their wavelength as they leave the star depends not only on how fast the star is moving, but also on how much energy the photons expend to escape the black hole’s powerful gravitational field. Near a black hole, gravity is much stronger than on Earth.
This is the first of many tests of general relativity Ghez’s research team will conduct on stars near the supermassive black hole. Among the stars that most interest her is S0-102, which has the shortest orbit, taking 11.5 years to complete a full orbit around the black hole. Most of the stars Ghez studies have orbits of much longer than a human lifespan.
For the original text & graphics see:
http://newsroom.ucla.edu/releases/einstein-general-relativity-theory-questioned-ghez
-- From a University of California press release forwarded by Karen Pollard.
14. How to Join the RASNZ
RASNZ membership is open to all individuals with an interest in
astronomy in New Zealand. Information about the society and its
objects can be found at
http://rasnz.org.nz/rasnz/membership-benefits
A membership form can be either obtained from 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'.
15. Kingdon-Tomlinson Fund
The RASNZ is responsible for recommending to the trustees of the Kingdon Tomlinson Fund that grants be made for astronomical projects. The grants may be to any person or persons, or organisations, requiring funding for any projects or ventures that promote the progress of astronomy in New Zealand. Applications are now invited for grants from the Kingdon-Tomlinson Fund. The application should reach the Secretary by 1 November 2019 for consideration by Council. Full details are set down in the RASNZ By-Laws, Section J. For an application form contact the RASNZ Executive Secretary, secretary@rasnz.org.nz
16. 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.
For an application form contact the Executive Secretary
secretary@rasnz.org.nz,
17. Quote
"Flying fish landed on the deck, albatrosses and sperm whales were constant companions, and on 9 August [1841] a meteor was seen to burst on the south-western sky. It was a prelude to a shower of shooting stars that was expected in the middle of the month. [James Clark] Ross made sure he had instructed all the men on watch what to look out for. So zealously did they throw themselves into their task that one of the men was reluctant to be relieved of his post, saying he was sure two or three stars were about to fall, as 'he'd been watching them and could see they were shaking!'" -- Michael Palin's 'Erebus - The Story of a Ship', p.124.
Alan Gilmore Phone: 03 680 6817
P.O. Box 57 alan.gilmore@canterbury.ac.nz
Lake Tekapo 7945
New Zealand
Comments