Tag Archives: 2017

The first detection of an electromagnetic counterpart to a gravitational wave event

Full AAO Media Release, published at 01:00am Sydney time, 17 October 2017, that I coordinated.

For the first time, astronomers have observed the afterglow of an event that was also detected in gravitational waves. The object, dubbed AT2017gfo, was a pair of in-spiralling neutron stars in a galaxy 130 million light years away. The death spiral was detected in gravitational waves, and the resulting explosion was followed by over 50 observatories world wide, including the AAO and other observatories here in Australia.

On August 17, the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO), based in the United States, detected a new gravitational wave event, called GW170817.

GW170817 is the fifth source of gravitational waves ever recorded. The first one was discovered in September 2015, for which three founding members of the LIGO collaboration were awarded the 2017 Nobel Prize in Physics.

The GW170817 data are consistent with the merging of two neutron stars and are unlike the four previous events, which were merging black holes.

Artist’s illustration of two merging neutron stars. The narrow beams represent the gamma-ray burst while the rippling space-time grid indicates the gravitational waves that characterize the merger. Swirling clouds of material ejected from the merging stars are a possible source of the light that was seen at lower energies. Credit: National Science Foundation/LIGO/Sonoma State University/A. Simonnet.

The Advanced-Virgo interferometer, based in Italy, was online at the time of the discovery and contributed to the localization of the new gravitational wave burst.

Based on information from LIGO and VIRGO, numerous telescopes immediately sprang into action to determine if an electromagnetic counterpart to the gravitational waves could be detected.

Meanwhile, NASA’s Fermi satellite independently reported a short burst of gamma-rays within 2 seconds of the merger event associated with GW170817, consistent with the area of sky from which LIGO and VIRGO detected their gravitational waves.

This gamma-ray detection at the same time and place triggered even greater interest from the astronomical community and resulted in more intense follow up observations in optical, infrared and radio wavelengths.

A team of scientists within the Dark Energy Survey (DES) collaboration, which includes researchers from the Australian Astronomical Observatory and other Australian institutions, working with astronomers at the Harvard-Smithsonian Center for Astrophysics (CfA) in the U.S., were among the first astronomers to observe the electromagnetic counterpart of GW170817 in optical wavelengths.

Using the 570-megapixel Dark Energy Camera (DECam) mounted at the 4m Blanco Telescope at Cerro Tololo Inter-American Observatory in Chile, DES identified the kilonova AT2017gfo in the nearby galaxy NGC 4993, located only 130 million light years from us, as the optical counterpart of GW170817.

Composite of detection images, including the discovery z image taken on August 18th and the g and r images taken 1 day later. Right: The same area two weeks later. Credit: Soares-Santos et al. and DES Collaboration.

“Because of its large field of view, the Dark Energy Camera was able to search almost the entire region where LIGO/VIRGO expected the gravitational wave source to be, and its exquisite sensitivity allowed us to make detailed measurements of the kilonova – the extremely energetic outburst created by the merging neutron stars,” AAO Instrument Scientist and DES Collaboration member Dr Kyler Kuehn stated.

A kilonova is similar to a supernova in some aspects, but it is different in others. It occurs when two neutron stars crash into each other. These events are thought to be the mechanism by which many of the elements heavier than iron, such as gold, are formed.

“But as impressive as it is, the Dark Energy Camera is only one of many instruments with a front row seat to this celestial spectacle. A lot of effort has gone into preparing dozens of telescopes around the world to search for electromagnetic counterparts to gravitational waves”, Dr Kuehn added.

Simultaneously to the DES study, a large group of Australian astronomers obtained follow up observations of the kilonova AT2017gfo at optical, infrared and radio wavelengths, using 14 Australian telescopes as part of the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) and other Australian programs.

Their data are consistent with the expected outburst and subsequent merger of two neutron stars, in agreement with the results derived for GW170817 by the LIGO/Virgo collaboration.

“Before this event, it was like we were sitting in an IMAX theatre with blindfolds on. The gravitational wave detectors let us ‘hear’ the movies of black hole collisions, but we couldn’t see anything. This event lifted the blindfolds and, wow, what an amazing show!!”, A/Professor Jeff Cooke, astronomer at Swinburne University who led many of the observations said.

The Australia team also conducted observations at the 3.9m Anglo-Australian Telescope (AAT), that is managed by the Australian Astronomical Observatory (AAO). Additional archive data from the 6dF survey obtained at the AAO’s 1.2m UK Schmidt Telescope were also used.

“The observations undertaken at the AAT place important constraints on the nature of the environment in which the kilonova occurred”, AAO astronomer Dr Chris Lidman said.

The follow up observations were not scheduled, but the excitement that this event generated in the astronomical community was so large that regular programs were placed on hold.

“Many astronomers dropped any other planned observation and used all the available resources to study this rare event”, said PhD candidate Igor Andreoni (Swinburne University and Australian Astronomical Observatory), first author of the scientific paper that will be published in the science journal “Publications of the Astronomical Society of Australia” (PASA).

The study also reveals that the host galaxy has not experienced significant star-formation during the last billion years. However, there is some evidence that indicates that NGC 4993 experienced a collision with a smaller galaxy not long time ago.

The position of the kilonova AT2017gfo, found in the external parts of NGC 4993, may suggest that the binary neutron star could have been part of the smaller galaxy.

Australian astronomers were thrilled to contribute to both the detection and the ongoing observations of the kilonova AT2017gfo, the electromagnetic counterpart to the gravitational wave event GW170817.

“We have been waiting and preparing for an event like this, but didn’t think it would happen so soon and in a galaxy that is so near to us. Once we were alerted of the gravitational wave detection, we immediately contacted a dozen telescopes and joined the worldwide effort to study this historic event. It didn’t let us down!”, A/Professor Jeff Cooke said.

“It was crucial to have telescopes placed in every continent, including Australia, to keep this rare event continuously monitored”, PhD candidate Igor Andreoni said.

“To me, this gravitational + electromagnetic wave combined detection is even more important than the initial detection that resulted in the Nobel Prize. This has changed the way the entire astronomical community operates”, AAO Instrument Scientist Dr Kyler Kuehn stated.

The first identification of the electromagnetic counterpart to a gravitational wave event is a milestone in the history of modern Astronomy, and opens a new era of multi-messenger astronomy.

More information:

AAO Media Release

AAO Media Release in Spanish / Nota de prensa del AAO en español

LIGO Media Release

DES Media Release

OzGrav Media Release

ESO Media Release

NASA Media Release

Article in The Conversation: “After the alert: radio ‘eyes’ hunt the source of the gravitational waves”, by Tara Murphy and David Kaplan

Article in The Conversation: “At last, we’ve found gravitational waves from a collapsing pair of neutron stars”, by David Blair

Multimedia, videos and animations:

Although there are many videos around there talking about this huge announcement, I particularly like this one by Derek Muller (Veritasium):


AAO #Scicomm events during Australian National Science Week 2017

The AAO organized and/or participated in 7 events during Australia’s National Science Week in August 2017, including the very successful and sold-out events “Star Tales of Winter Nights” and “Stargazing in the Park”.

Astronomers at the AAO’s “Star Tales of Winter Nights” event at the Powerhouse Museum during National Science Week 2017. From left to right: Adam Schaefer, Dr Devika Kotachery, Dr. Ángel López-Sánchez (MC), Carlos Bacigalupo and Rebecca Brown. Credit: Ángel López-Sánchez.

The event “Star Tales of Winter Nights”, hosted at Sydney’s Powerhouse Museum had a very similar structure than our ViVID Sydney Ideas events: 5 astronomers talking about science and later answering questions from the audience. The speakers were Rebecca Brown, Adam Schaefer, Dr Devika Kotachery, Carlos Bacigalupo and myself. This event was another big success for the AAO.

Setting up the telescopes for AAO’s “Stargazing in the Park” in Sydney’s Centennial Park. Credit: Ángel R. López-Sánchez.

AAO’s Ángel López-Sánchez, Stuart Ryder and Duncan Wright (from left to right) ready for “Stargazing in the Park” in Sydney’s Centennial Park. Credit: Ángel R. López-Sánchez.

On the other hand, the “Stargazing in the Park” in Sydney’s Centennial Park was another sold-out event, with more than 120 people enjoying first a short lecture about the AAO and introduction to stargazing and later looking at the sky through the telescopes.

AAO’s Stuart Ryder attending visitors at the AAO desk during the “Science and Tech” expo at Chatswood Library on Saturday 12th August. Credit: Ángel López-Sánchez.

During National Science Week 20017 the AAO also participated in two of the events organized by the recently created “North Sydney Science Hub” . First on Saturday 12th August in the “Science and Tech” expo at Chatswood Library, and later in the Public DiscussionBig Data And Visual Analytics – What is it good for?”, on Thursday 17th August, also at Chatswood Library, being myself one of the panelists of the discussion.

Panel for the Public Discussion “Big Data And Visual Analytics – What is it good for?”, on Thursday 17th August, also at Chatswood Library. From left to right: Mark Ballico (NMI), Tomasz Bednarz (Data61 and UNSW Art & Design), Angela (CSIRO) and Ángel R. López-Sánchez (AAO.MQU).  Credit: Ángel R. López-Sánchez.

Historic ESO-Australia agreement

This is BIG. Australian astronomers have tried for almost 2 decades to be part of the European Southern Observatory (ESO). Yesterday, 11th July 2017, at a ceremony happening during the Annual Meeting of the Astronomical Society of Australia (ASA) in Canberra, Australia, ESO’s Director General, Tim de Zeeuw, and the Australian Minister for Industry, Innovation and Science, Arthur Sinodinos, signed a 10 years Strategic Partnership between Australia and ESO.

Image composition showing all the ESO observatories and the Headquarters. Credit: ESO/M. Kornmesser.

Following the ESO-Australia Strategic Agreement, Australian astronomers (including me!) will have access to telescope time at La Silla and Paranal Observatories in Chile. The ESO-Australia Strategic Agreement also provides crucial opportunities for Australian influence and technical and scientific input, stimulating international research and industry collaborations.

This is particularly important for the Australian Astronomical Observatory (AAO), as we are developing key instrumentation for ESO (as the ESOP positioner for the VISTA telescope), and that was a key part of the deal, with new opportunities to develop further telescope instrumentation in the nearby future. That also means an important re-arrangement within the AAO, which details are still unknown, but in which we’ll give our best.

At a ceremony in Canberra, Australia, on 11 July 2017, an arrangement was signed to begin a ten-year strategic partnership between ESO and Australia. The partnership will further strengthen ESO’s programme, both scientifically and technically, and will give Australian astronomers and industry access to the La Silla Paranal Observatory. It may also be the first step towards Australia becoming an ESO Member State.
This picture shows all the signatories of the arrangement. From left to right: Virginia Kilborn, President of the Astronomical Society of Australia, Warrick Couch, Director of the Australian Astronomical Observatory, Sue Weston, Deputy Secretary, Department of Industry, Innovation and Science, Senator the Hon Arthur Sinodinos, Minister for Industry, Innovation and Science, Tim de Zeeuw, ESO Director General, Brian Schmidt, Vice Chancellor of the Australian National University, Laura Comendador, Head of the ESO Cabinet and Patrick Geeraert, ESO Director of Administration. Credit: Australian Government.

The Australian Government will invest $129 million over 10 years in the partnership, including the $26.1 million already announced for 2017-2018 Australian Budget. This may also be the first step towards Australia becoming an ESO Member State.

Exciting times await!

More details:

“Stargazing in the Calyx”, new Science Communication Event series at Sydney’s Botanic Gardens

Article originally written by Ángel R. López-Sánchez for the “AAO Observer” 132, August 2017.

In June 2017 the Australian Astronomical Observatory (AAO) started a new Science Communication collaboration with historic Sydney’s Royal Botanic Gardens. The events “Stargazing in the Calyx” combine a short talk given by an astronomer followed by a stargazing session with amateur telescopes.

People are enjoying the view of the sky through amateur telescopes during the “Stargazing in the Calyx” science communication event at Sydney’s Botanic Gardens on Tuesday 4th July 2017. Credit: Christina McGhee (Sydney’s Botanic Gardens).

The first of these events was held on Monday 19th June 2017. It was so successful that the following “Stargazing in the Calyx” session, scheduled on Tuesday 4th July, was sold out in just 8 minutes after the tickets were available.

The organization of these events have received a hugely positive feedback, both about the venue (the brand-new “The Calyx” building at Sydney’s Botanic Gardens) and the atmosphere (people enjoyed dinner with drinks under the stars) and the entertaining and knowledgeable talks about the Southern Sky (given by AAO and Macquarie University astronomer Ángel López-Sánchez).

AAO/MQU astronomer Ángel López-Sánchez giving his talk “Introduction to the Southern Sky” as part of the “Stargazing in the Calyx” event at Sydney’s Botanic Gardens on Monday 19th June 2017. Credit: Christina McGhee (Sydney’s Botanic Gardens).

Besides some clouds and Sydney’s light pollution, participants really enjoyed the views of planets Jupiter and Saturn and the Moon through the telescopes, as well as observing globular cluster Omega Centauri and the famous “Jewel Box” star cluster in the Southern Cross, as well as learn to recognize the constellations of the winter nights at the southern hemisphere. Some of the telescopes were kindly provided by CSIRO, Sydney University, Macquarie University and some amateur astronomers who were also invited to these events.

The next “Stargazing a the Calyx” event is scheduled on Tuesday 3rd of October. We expect they will be repeated each 1 or 2 months.

“The Story of Light: Surveying the Cosmos”, in Vivid Sydney Ideas 2017

Article originally written by Ángel R. López-Sánchez for the “AAO Observer” 132, August 2017.

Following the success of our sold-out Event “The Story of Light – The Astronomer’s Perspective” for ViVID Sydney Ideas 2015, and “The Story of Light – Deciphering the data encoded on the cosmic light” (see photos and the video of this event), the Australian Astronomical Observatory (AAO) continued its collaboration with ViVID Sydney 2017 organizing “The Story of Light – Surveying the Cosmos”.

This successful science communication event was held at the Powerhouse Museum (Sydney) on Sunday 4th June 2017. Having an audience of 300 people, it was sold out more than two weeks before the event.

“The Story of Light – Surveying the Cosmos” was connected to the 2017 Southern Cross Astrophysics Conference: Surveying the Cosmos, the Science from massively multiplexed surveys, that was held in Luna Park, Sydney, between 5th and 9th June 2017.

Poster for the AAO’s “The Story of Light – Surveying the Cosmos” Science Communication event for Vivid Sydney Ideas 2017. Credit: Angel R. Lopez-Sanchez.

In this event, five professional astrophysicists discussed how astronomers map the Cosmos using the big data collected with optical and radio telescopes by large astronomical surveys.

How do astronomers explore the Universe? Astrophysicists use extremely sensitive telescopes and instruments to collect the light emitted by stars, gas and galaxies. The analysis of this data provides the information needed to unlock the mysteries of the Cosmos.

However, this is not an easy task. Over the last two decades large international collaborations have been formed with the aim to map the skies, catalogue celestial objects, extract their properties and perform statistical analyses. These large astronomical surveys are now providing major advances in our understanding of the Cosmos at all scales, from searching for planets around other stars to detecting gravitational waves.

Australia is at the forefront of these collaborations thanks to the unique instruments at the Anglo-Australian Telescope (AAT) and the development of radio-interferometers as the Australian SKA Pathfinder (ASKAP).

Panel members and MC of AAO’s “The Story of Light – Surveying the Cosmos” Science Communication event for Vivid Sydney Ideas 2017. From left to right: Katie Mack, Alan Duffy, Simon O’Toole, Tara Murphy and Ángel López-Sánchez. Credit: Duncan Wright (AAO/UNSW).

The panel members were Dr. Simon O’Toole (Australian Astronomical Observatory), who talked about surveying stars and exoplanets, Dr. Ángel R. López-Sánchez (Australian Astronomical Observatory / Macquarie University), who discussed how we surveying the galaxies, A/Prof. Tara Murphy (University of Sydney / CAASTRO), who invited us to surveying the invisible Universe, and Dr. Katie Mack (University of Melbourne), who talked about surveying the deep Universe. The event was hosted by famous astrophysicist and science communicator A/Prof. Alan R. Duffy (Swinburne University).

After short (15 minutes) talks, the panel answered questions about the Universe and challenging Physics questions as the nature of the dark matter and the dark energy. They also received some more philosophical questions that engaged the audience.

More information:

AAO joins organization of International Science Communication Festival “Pint of Science”

Article originally written by Ángel R. López-Sánchez for the “AAO Observer” 132, August 2017.

In 2017 the Australian Astronomical Observatory joined the international Science Communication festival Pint of Science. The festival started in the UK and runs every May in over 150 cities across 12 different countries, including Australia. This year Pint of Science took place in 13 cities across Australia (including Sydney) over 15, 16 and 17 May 2017.

The Pint of Science festival aims to promote Science and Science Communication in a very relaxing atmosphere: in a pub with a drink. It brings scientists to a local pub to discuss their latest research and findings with the public.

Poster of Sydney’s “Atoms to Galaxies” for Pint of Science Australia 2017. Credit: Ángel R. López-Sánchez.

The Australian Astronomical Observatory joined CSIRO, the ARC Centre of Excellence CAASTRO, and the Spanish Researchers in Australia-Pacific (SRAP) association as a sponsor of Sydney’s Pint of Science Festival in 2017. Our astronomer Ángel López-Sánchez (AAO/MQU) co-leaded the organization of the “Atoms to Galaxies” talks. These sessions included talks about Physics, Math, Chemistry and Astronomy and were hosted at Bar Cleveland, in Surry Hills.

Sydney’s “Atoms to Galaxies” program (which was the largest for Pint of Science Australia 2017) included talks about applied maths, search for exoplanets, explore quantum computing, play with the light, learn the origin of the chemical elements, map distant galaxies and challenge the laws of Physics.

Angel López-Sánchez during his talk “The Cosmic Origin of the Elements”.

The first night, “Elements in Space”, included talks by AAO astronomer and engineer Kyler Kuehn, who talked about astronomy neutrinos presenting the work he conducted in Antarctica for his PhD Thesis, and by AAO and Macquarie University astronomer Ángel López-Sánchez, who transported the audience to distant stars and galaxies to know when and how the atoms that compose our body were created.

Kyler Kuehn (AAO) before starting his talk “Pint of neutrinos”. Credit: Ángel López-Sánchez.

In the third night, “Decodifying the Light of the Cosmos”, AAO astronomer an eResearch administrator Simon O’Toole described how we use the light collected by optical telescopes to search for planets around other stars, with the ultimate aim of finding an “Earth 2.0”.

Simon O’Toole during his talk for “Pint of Science” festival “Searching for Earth 2.0”. Credit: Angel López-Sánchez.

Astronomers George Hobbs (CSIRO), Luke Barnes (University of Sydney) and Baerbel Koribalski (CSIRO), as well as physicists Dr. Sergio León-Saval (University of Sydney) and Prof. Jason Twamley (Macquarie University), and mathematician Emi Tanaka (University of Sydney) completed the “Atoms to Galaxies” program.

Rebecca Brown during her talk for “Pint of Science” festival explaining how the Starbugs developed for the new TAIPAN instrument at the UKST work. Credit: Rebecca Brown.

Besides organizing Sydney’s “Atoms to Galaxies” talks for Pint of Science Australia 2017, the Australian Astronomical Observatory was also present in the “Tech me out!” session Space Oddities on Wednesday 17th May. AAO’s optical engineer Rebecca Brown gave the talk “Capturing the Light of the Universe“, where she summarized the technologies used in optical telescopes, how they work and what we can learn, including example technologies developed at the AAO.



The details of the talks for the “Atoms to Galaxies” events in Pint of Science Sydney 2017  (info extracted from this AAO website) were:

Monday 15th May: Elements in Space

Tonight we will explore the conjunction between math, chemistry and astronomy. First Dr. Emi Tanaka (University of Sydney) will talk about how statistics feeds us, introducing the basic mathematical tools of statistics and their application in agriculture. Then Dr. Lamiae Azizi (University of Sydney) will be talking about how mathematical sciences coupled with computing have the potential to improve our lives. Finally, astrophysicist and science communicator Dr. Ángel López-Sánchez (Australian Astronomical Observatory / Macquarie University) will transport us to distant stars and galaxies to know when and how the atoms that compose our body were created.

More details and tickets for “Elements in Space” in the Pint of Science website.

Tuesday 16th May: Challenging the Laws of Physics

Tonight we will aim to change the Laws of Physics. Our first speaker, Prof. Jason Twamley (Macquarie University), will talk about quantum computing and why this research is so important. Then, astrophysicist Dr. George Hobbs (CSIRO) will explain what mysterious pulsars are and why their study is so important for physicists. After the break, cosmologist Dr. Luke Barnes (University of Sydney) will challenge our understanding of the physical constants to demonstrate that we live in a finely-tuned Universe.

More details and tickets for “Challenging the Laws of Physics” in the Pint of Science website.

Wednesday 17th May: Decodifying the Light of the Cosmos

Tonight we seek to get a better understanding of what the light can tell us about the Universe. Our first speaker, Dr. Sergio León-Saval (University of Sydney) will show us some of the photonic instruments that are now used in optical telescopes to direct the light of the stars from the optics to the detectors. In the second talk Dr. Simon O’Toole (Australian Astronomical Observatory) will describe how we use the light collected by optical telescopes to search for planets around other stars, with the ultimate aim of finding an “Earth 2.0”. Lastly, Dr. Baerbel Koribalski (CSIRO Astronomy and Space Science) will describe how radio-astronomers study the light of distant galaxies emitted in radio waves using facilities as the new “Australian SKA Pathfinder” (ASKAP) interferometer.

More details and tickets for “Decodifying the Light of the Cosmos” in the Pint of Science website.

Successful BBC and ABC Stargazing Live TV events at Siding Spring Observatory

Article originally written by Ángel R. López-Sánchez for the “AAO Observer” 132, August 2017. Credits of all the photos: Ángel R. López-Sánchez.

Colorful lights in dome of our Anglo-Australian Telescope in preparation for the Stargazing Live TV shows.

During two weeks in late March and early April 2017, famous physicist and TV presenter Professor Brian Cox co-hosted two “Stargazing TV” shows emitted live from Siding Spring Observatory in the BBC and in the ABC. The stage of these major TV events was our Anglo-Australian Telescope, (AAT) at Siding Spring Observatory, on the edge of the Warrumbungle National Park near Coonabarabran, NSW.

BBC Stargazing Live shows at Siding Spring Observatory were emitted on the early morning of Wednesday 29th, Thursday 30th and Friday 31st March 2017 (evenings of the previous days in the UK). BBC Stargazing Live TV shows were hosted by Professor Brian Cox and TV presenter and comedian Dara Ó Briain, with the participation of biologist and BBC presenter Liz Bonnin and Broome-based amateur astronomer Greg Quicke (who was very popular in social media, receiving the nickname of #SpaceGandalf).

During BBC Stargazing Live astrophysicist and science communicator Lisa Harvey-Smith (CSIRO) was also interviewed. Astronomer and journalist Chris Lintott (Oxford University) was in charge of reporting the news of the citizen science project “The Search for Planet 9“, led by astronomers at the Australian National University and launched in the first episode of BBC Stargazing Live. This citizen science project uses images taken with the Skymapper telescope at Siding Spring Observatory to search for a new planet in our Solar System.

#StargazingABC live episodes were emitted the following week (Tuesday 4th, Wednesday 5th and Thursday 6th April 2017). Hosts Professor Brian Cox and TV presenter Julia Zemiro were joined by astronomers to inspire Australia to explore our Universe and tackle astronomy’s most intriguing questions. Astronomer Lisa Harvey-Smith (CSIRO) also participated as TV presenter for the #StargazingABC shows.

AAO’s Fred Watson, Steve Lee and David Malin were interviewed several times during the ABC and BBC Stargazing Live shows.

SAMI observers at the Anglo-Australian Telescope shared the dome with ABC crew while preparing instrument and telescope for observations on the afternoon of Sunday 2nd April.

For #StargazingABC first episode, the Milky Way, AAO astronomers Ángel López-Sánchez and Steve Lee prepared a new astronomical color image using data taken with the CACTI auxiliary camera of the AAT, which was broadcasted in the episode. This image shows Diffuse gas and dust in the heart of the Carina Nebula. The bright star is Eta Carinae, a massive double star at the end of its live that will soon explode as a supernova. The “Keyhole” is the dark cloud in the centre of the image.

Both Stargazing Live ABC events were very successful. #StargazingABC live episodes reached 2.7 million viewers across metro and regional Australia. They also had a huge impact in social media. ABC 1st TV episode reached over 240K people and had more than 8K reactions in Facebook, comments and shares, similar numbers to those obtained with ABC TV’s New Year’s Eve Family Fireworks stream. Regarding Twitter, the #StargazingABC hashtag reached 18.4 million users and produced 16.8K tweets from 6.3K unique contributors. 12.8K of these tweets were produced during the broadcasts, making #StargazingABC trend no.1 in Australia.

Credits of all the photos: Ángel R. López-Sánchez.

More information: AAO news: ABC Stargazing Live at the AAT.