̽��ֱ�� of Cambridge - Dafydd Wyn Evans

Farewell, Gaia: spacecraft operations come to an end

sc604 — Thu, 27 Mar 2025 10:27:38 +0000

On 27 March 2025, Gaia’s control team at ESA’s European Space Operations Centre switched off the spacecraft’s subsystems and sent it into a ‘retirement orbit’ around the Sun.

Though the spacecraft’s operations are now over, the scientific exploitation of Gaia’s data has just begun.

Launched in 2013, Gaia has transformed our understanding of the cosmos by mapping the positions, distances, motions, and properties of nearly two billion stars and other celestial objects. It has provided the largest, most precise multi-dimensional map of our galaxy ever created, revealing its structure and evolution in unprecedented detail.

̽��ֱ��mission uncovered evidence of past galactic mergers, identified new star clusters, contributed to the discovery of exoplanets and black holes, mapped millions of quasars and galaxies, and tracked hundreds of thousands of asteroids and comets. ̽��ֱ��mission has also enabled the creation of the best visualisation of how our galaxy might look to an outside observer.

“ ̽��ֱ��data from the Gaia satellite has and is transforming our understanding of the Milky Way, how it formed, how it has evolved and how it will evolve,” said Dr Nicholas Walton from Cambridge’s Institute of Astronomy, lead of the Gaia UK project team. “Gaia has been in continuous operation for over 10 years, faultless, without interruption, reflecting the quality of the engineering, with significant elements of Gaia designed and built in the UK. But now it is time for its retirement. Gaia has finished its observations of the night sky. But the analysis of the Gaia mission data continues. Later in 2026 sees the next Gaia Data Release 4, to further underpin new discovery unravelling the beauty and mystery of the cosmos.”

Gaia far exceeded its planned lifetime of five years, and its fuel reserves are dwindling. ̽��ֱ��Gaia team considered how best to dispose of the spacecraft in line with ESA’s efforts to responsibly dispose of its missions.

They wanted to find a way to prevent Gaia from drifting back towards its former home near the scientifically valuable second Lagrange point (L2) of the Sun-Earth system and minimise any potential interference with other missions in the region.

“Switching off a spacecraft at the end of its mission sounds like a simple enough job,” said Gaia Spacecraft Operator Tiago Nogueira. “But spacecraft really don’t want to be switched off.

“We had to design a decommissioning strategy that involved systematically picking apart and disabling the layers of redundancy that have safeguarded Gaia for so long, because we don’t want it to reactivate in the future and begin transmitting again if its solar panels find sunlight.”

On 27 March, the Gaia control team ran through this series of passivation activities. One final use of Gaia’s thrusters moved the spacecraft away from L2 and into a stable retirement orbit around the Sun that will minimise the chance that it comes within 10 million kilometres of Earth for at least the next century.

̽��ֱ��team then deactivated and switched off the spacecraft’s instruments and subsystems one by one, before deliberately corrupting its onboard software. ̽��ֱ��communication subsystem and the central computer were the last to be deactivated.

Gaia’s final transmission to ESOC mission control marked the conclusion of an intentional and carefully orchestrated farewell to a spacecraft that has tirelessly mapped the sky for over a decade.

Though Gaia itself has now gone silent, its contributions to astronomy will continue to shape research for decades. Its vast and expanding data archive remains a treasure trove for scientists, refining knowledge of galactic archaeology, stellar evolution, exoplanets and much more.

“No other mission has had such an impact over such a broad range of astrophysics. It continues to be the source of over 2,000 peer-reviewed papers per year, more than any other space mission,” said Gaia UK team member Dr Dafydd Wyn Evans, also from the Institute of Astronomy. “It is sad that its observing days are over, but work is continuing in Cambridge, and across Europe, to process and calibrate the final data so that Gaia will still be making its impact felt for many years in the future.”

A workhorse of galactic exploration, Gaia has charted the maps that future explorers will rely on to make new discoveries. ̽��ֱ��star trackers on ESA’s Euclid spacecraft use Gaia data to precisely orient the spacecraft. ESA’s upcoming Plato mission will explore exoplanets around stars characterised by Gaia and may follow up on new exoplanetary systems discovered by Gaia.

̽��ֱ��Gaia control team also used the spacecraft’s final weeks to run through a series of technology tests. ̽��ֱ��team tested Gaia’s micro propulsion system under different challenging conditions to examine how it had aged over more than ten years in the harsh environment of space. ̽��ֱ��results may benefit the development of future ESA missions relying on similar propulsion systems, such as the LISA mission.

̽��ֱ��Gaia spacecraft holds a deep emotional significance for those who worked on it. As part of its decommissioning, the names of around 1500 team members who contributed to its mission were used to overwrite some of the back-up software stored in Gaia’s onboard memory.

Personal farewell messages were also written into the spacecraft’s memory, ensuring that Gaia will forever carry a piece of its team with it as it drifts through space.

As Gaia Mission Manager Uwe Lammers put it: “We will never forget Gaia, and Gaia will never forget us.”

̽��ֱ��Cambridge Gaia DPAC team is responsible for the analysis and generation of the Gaia photometric and spectro-photometric data products, and it also generated the Gaia photometric science alert stream for the duration of the satellite's in-flight operations.

Adapted from a media release by the European Space Agency.

̽��ֱ��European Space Agency’s Gaia spacecraft has been powered down, after more than a decade spent gathering data that are now being used to unravel the secrets of our home galaxy.

ESA/Gaia/DPAC, Stefan Payne-Wardenaar

Artist's impression of the Milky Way

̽��ֱ��text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

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Latest Gaia data release reveals rare lenses, cluster cores and unforeseen science

sc604 — Tue, 10 Oct 2023 12:47:51 +0000

Gaia is mapping our galaxy and beyond in multi-dimensional detail, completing the most accurate stellar census ever. ̽��ֱ��mission is painting a detailed picture of our place in the Universe, enabling us to better understand the diverse objects within it.

̽��ֱ��mission’s latest data release provides new and improved insights into the space around us. ̽��ֱ��release also brings findings that go far beyond what Gaia was initially designed to discover and digs deep into our cosmic history.

“This focused product data release will open up new insights across astronomy, from the precise orbits of asteroids in our Solar System, to quasar discovery in the distant cosmos,” said Dr Nicholas Walton from Cambridge’s Institute of Astronomy, lead of the UK Gaia Project team and ESA Gaia Science Team member. “It demonstrates the breadth of science enabled by Gaia, and the role of Cambridge and UK Gaia teams in the creation of these data products. This release represents but a small taste of the riches to be revealed with the publication of the next full release, Gaia DR4.”

So – what’s new from Gaia?

Half a million new stars: Gaia's observing mode extended to unlock cluster cores

Gaia’s third data release (DR3) contained data on over 1.8 billion stars, building a pretty complete view of the Milky Way and beyond. However, there remained gaps in our mapping. Gaia had not yet fully explored areas of sky that were especially densely packed with stars, leaving these comparatively unexplored – and overlooking stars shining less brightly than their many neighbours.

Globular clusters are a key example of this. These clusters are some of the oldest objects in the Universe, making them especially valuable to scientists looking at our cosmic past. Unfortunately, their bright cores, chock-full of stars, can overwhelm telescopes attempting to get a clear view. As such, they remain missing pieces in our maps of the Universe.

To patch the gaps in our maps, Gaia selected Omega Centauri, the largest globular cluster that can be seen from Earth. Rather than just focusing on individual stars, as it typically would, Gaia enabled a special mode to truly map a wider patch of sky surrounding the cluster’s core every time the cluster came into view.

“In Omega Centauri, we discovered over half a million new stars Gaia hadn't seen before – from just one cluster!” says lead author Katja Weingrill of the Leibniz-Institute for Astrophysics Potsdam (AIP), Germany, and a member of the Gaia collaboration.

“Through a new use of one of Gaia’s specialised engineering modes, we have been able to generate an imaging catalogue of some of the densest stellar fields in our galaxy,” said Dr Dafydd Wyn Evans, lead of the Gaia photometric development team. “This is enabling us to provide a more complete view of all components of the Milky Way, including the cores of Globular Clusters, some of the oldest structures in our Galaxy.”

This finding not only meets but actually exceeds Gaia’s planned potential. ̽��ֱ��team used an observing mode designed to ensure that all of Gaia’s instruments are running smoothly.

“ ̽��ֱ��Gaia Sky Mapper images required the development of a new processing pipeline to measure the accurate brightness of the hundreds of thousands faint stars not seen by Gaia before,” said Dr Francesca De Angeli, lead of Gaia’s Photometric Data Processing Centre in Cambridge. “This rich data probes regions of the sky previously unseen by Gaia, and fills in important gaps in earlier data releases.”

̽��ֱ��new stars revealed in Omega Centauri mark one of the most crowded regions explored by Gaia so far.

Gaia is currently exploring eight more regions in this way, with the results to be included in Gaia Data Release 4. These data will help astronomers to truly understand what is happening within these cosmic building blocks, a crucial step for scientists aiming to confirm the age of our galaxy, locate its centre, figure out whether it has gone through any past collisions, verify how stars change through their lifetimes, constrain our models of galactic evolution, and ultimately infer the possible age of the Universe itself.

Looking for lenses: Gaia the accidental cosmologist

While Gaia was not designed for cosmology, its new findings peer deep into the distant Universe, hunting for elusive and exciting objects that hold clues to some of humanity’s biggest questions about the cosmos: gravitational lenses.

Gravitational lensing occurs when the image of a faraway object becomes warped by a disturbing mass – a star or galaxy, for instance – sitting between us and the object. This intermediate mass acts as a giant magnifying glass, or lens, that can amplify the brightness of light and cast multiple images of the faraway source onto the sky. These rare configurations hold immense scientific value, revealing clues about the earliest days of the Universe.

̽��ֱ��team identified the candidates from an extensive list of possible quasars (including those from Gaia DR3). Five of the possible lenses are potential Einstein crosses, rare lensed systems with four different image components shaped like a cross. (See 12 such configurations discovered by Gaia in 2021.)

Finding lensed quasars is challenging. A lensed system’s constituent images can clump together on the sky in misleading ways, and most are very far away, making them faint and tricky to spot.

Extending Gaia’s value into cosmology brings synergy with ESA’s Euclid mission, recently launched on its quest to explore the dark Universe. While both focus on different parts of the cosmos – Euclid on mapping billions of galaxies, Gaia on mapping billions of stars – the lensed quasars discovered by Gaia can be used to guide future exploration with Euclid.

Asteroids, stacked starlight and pulsating stars

Other papers published today offer further insight into the space around us, and the diverse and sometimes mysterious objects within it.

One reveals more about 156,823 of the asteroids identified as part of Gaia DR3. ̽��ֱ��new dataset pinpoints the positions of these rocky bodies over nearly double the previous timespan, making most of their orbits – based on Gaia observations alone – 20 times more precise. In the future, Gaia DR4 will complete the set and include comets, planetary satellites and double the number of asteroids, improving our knowledge of the small bodies in nearby space.

Another paper maps the disc of the Milky Way by tracing weak signals seen in starlight, faint imprints of the gas and dust that floats between the stars. ̽��ֱ��Gaia team stacked six million spectra to study these signals, forming a dataset of weak features that have never been measured in such a large sample. ̽��ֱ��dataset will hopefully allow scientists to narrow down the source of these signals, which the team suspects to be a complex organic molecule. Knowing more about where this signal comes from helps us to study the physical and chemical processes active throughout our galaxy, and to understand more about the material lying between stars.

Finally, a paper characterises the dynamics of 10,000 pulsating and binary red giant stars in by far the largest such database available to date. These stars were part of a catalogue of two million variable star candidates released in Gaia DR3, and are key when calculating cosmic distances, confirming stellar characteristics, and clarifying how stars evolve throughout the cosmos. ̽��ֱ��new release provides a better understanding of how these stars change over time.

“This data release further demonstrates Gaia’s broad and fundamental value – even on topics it wasn’t initially designed to address,” said Timo Prusti, Project Scientist for Gaia at ESA.

̽��ֱ��next steps

Gaia’s previous Data Release, Gaia DR3, came on 13 June 2022. It was the most detailed survey of the Milky Way to date, and a treasure trove of data on strange ‘starquakes’, asymmetrically moving stars, stellar DNA and more. Gaia DR3 contained new and improved details for almost two billion stars in the Milky Way, and included the largest catalogues of binary stars, thousands of Solar System objects, and – more distantly and outside of our galaxy – millions of galaxies and quasars.

̽��ֱ��mission’s next Data Release, Gaia DR4, is expected not before the end of 2025. It will build upon both Gaia DR3 and this interim focused product release to further improve our understanding of the multi-dimensional Milky Way. It will refine our knowledge of stars’ colours, positions, and movements; resolve variable and multiple star systems; identify and characterise quasars and galaxies; list exoplanet candidates; and more.

Adapted from an ESA press release.

̽��ֱ��European Space Agency’s Gaia mission has released a goldmine of knowledge about our galaxy and beyond. Among other findings, the star surveyor has surpassed its planned potential to reveal half a million new and faint stars in a massive cluster, identified over 380 possible cosmic lenses, and pinpointed the positions of more than 150,000 asteroids within the Solar System.

This release represents but a small taste of the riches to be revealed with the publication of the next full release, Gaia DR4

Nicholas Walton

ESA/Gaia/DPAC

Gaia view of Omega Centauri

̽��ֱ��text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

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Largest chemical map of the Milky Way unveiled

sc604 — Mon, 13 Jun 2022 07:59:38 +0000

̽��ֱ��European Space Agency’s (ESA) Gaia mission has released a new treasure trove of data about our home galaxy, including stellar DNA, asymmetric motions, strange ‘starquakes’, and other fascinating insights.

Gaia creates richest star map of our Galaxy – and beyond

sc604 — Wed, 25 Apr 2018 09:41:39 +0000

A multitude of discoveries are on the horizon after today’s much-awaited release, which is based on 22 months of charting the sky, as part of Gaia’s mission to produce the largest, most precise three-dimensional map of our Galaxy ever created. ̽��ֱ��new data includes positions, distance indicators and motions of more than one billion stars, along with high-precision measurements of asteroids within our Solar System and stars beyond our own Milky Way Galaxy.

Preliminary analysis of this phenomenal data reveals fine details about the makeup of the Milky Way’s stellar population and about how stars move, essential information for investigating the formation and evolution of our home Galaxy.

“ ̽��ֱ��observations collected by Gaia are redefining the foundations of astronomy,” said Günther Hasinger, ESA Director of Science. “Gaia is an ambitious mission that relies on a huge human collaboration to make sense of a large volume of highly complex data. It demonstrates the need for long-term projects to guarantee progress in space science and technology and to implement even more daring scientific missions of the coming decades.”

This unique mission is reliant on the work of Cambridge researchers who collect the vast quantities of data transmitted by Gaia to a data processing centre at the ̽��ֱ��, overseen by a team at the Institute of Astronomy.

“There is hardly a branch of astrophysics which will not be revolutionised by Gaia data,” said Cambridge’s Professor Gerry Gilmore, Principal Investigator for the UK participation in the Gaia Data Processing and Analysis Consortium, and one of the original proposers of the mission to ESA. “ ̽��ֱ��global community will advance our understanding of what we see, where it came from, what it is made from, how it is changing. All this is made freely available to everyone, based on the dedicated efforts of hundreds of people.”

Gaia was launched in December 2013 and started science operations the following year. ̽��ֱ��first data release, based on just over one year of observations, was published in 2016; it contained distances and motions of two million stars. ̽��ֱ��new data release, which covers the period between 25 July 2014 and 23 May 2016, pins down the positions of nearly 1.7 billion stars, and with a much greater precision. For some of the brightest stars in the survey, the level of precision equates to Earth-bound observers being able to spot a Euro coin lying on the surface of the Moon.

With these accurate measurements it is possible to separate the parallax of stars – an apparent shift on the sky caused by Earth’s yearly orbit around the Sun – from their true movements through the Galaxy. ̽��ֱ��new catalogue lists the parallax and velocity across the sky, or proper motion, for more than 1.3 billion stars. From the most accurate parallax measurements, about ten percent of the total, astronomers can directly estimate distances to individual stars.

̽��ֱ��comprehensive dataset provides a wide range of topics for the astronomy community. As well as positions, the data include brightness information of all surveyed stars and colour measurements of nearly all, plus information on how the brightness and colour of half a million variable stars change over time. It also contains the velocities along the line of sight of a subset of seven million stars, the surface temperatures of about a hundred million and the effect of interstellar dust on 87 million.

Gaia also observes objects in our Solar System: the second data release comprises the positions of more than 14,000 known asteroids, which allows precise determination of their orbits. A much larger asteroid sample will be compiled in Gaia’s future releases.

Further afield, Gaia closed in on the positions of half a million distant quasars, bright galaxies powered by the activity of the supermassive black holes at their cores. These sources are used to define a reference frame for the celestial coordinates of all objects in the Gaia catalogue, something that is routinely done in radio waves but now for the first time is also available at optical wavelengths.

Major discoveries are expected to come once scientists start exploring Gaia’s new release. An initial examination performed by the data consortium to validate the quality of the catalogue has already unveiled some promising surprises – including new insights on the evolution of stars.

̽��ֱ��team in Cambridge is led by Dr Floor van Leeuwen, Dr Dafydd Wyn Evans, Dr Francesca De Angeli and Dr Nicholas Walton.

“This data release has proven an exciting challenge to process from spacecraft camera images to science-ready catalogues,” said De Angeli, head of the Cambridge processing centre. “More sophisticated strategies and updated models will be applied to the Gaia data to achieve even more precise and accurate photometric and spectrophotometric information, which will enable even more exciting scientific investigations and results.”

“Gaia has so far observed each of its more than 1.7 billion sources on average about 200 times,” said Evans. “This very large data set has to have all the changing satellite and sky responses removed, and everything converted on to a well-defined scale of brightness and colour. While a huge challenge, it is worth it.”

“Groups of dwarf galaxies, including the Magellanic Clouds, can now be observed to be moving around in very similar orbits, hinting at a shared formation history,” said van Leeuwen, Project Manager for the UK and European photometric processing work. “Similarly, a pair of globular clusters has been observed with very similar orbital characteristics and chemical composition, again pointing towards a shared history of formation. ̽��ֱ��accurate observed motions and positions of the globular clusters and dwarf galaxies provide tracers of the overall mass distribution of our galaxy in a way that has not been possible with this level of accuracy before.”

“ ̽��ֱ��Gaia data will be a globally accessible resource for astronomical research for decades to come, enabling the future research of today's young astronomers in the UK, Europe and the World,” said Walton, a member of the ESA Gaia Science Team. “Gaia is raising excitement and opportunity, bringing the next generation of researchers together to tackle many key questions in our understanding of the Milky Way.”

More data releases will be issued in future years, with the final Gaia catalogue to be published in the 2020s. This will be the definitive stellar catalogue for the foreseeable future, playing a central role in a wide range of fields in astronomy.

“This vast step into a new window on the Universe is a revolution in our knowledge of the contents, motions and properties of our local Universe,” said Gilmore. “We look forward to the international astronomical community building on this European project, with its major UK contributions, to interpret these Gaia data to revolutionise our understanding of our Universe. This is a magnificent harvest, but cornucopia awaits. We are all proud to be part of this magnificent project.”

Adapted from an ESA press release.

̽��ֱ��European Space Agency’s Gaia mission has produced the richest star catalogue to date, including high-precision measurements of nearly 1.7 billion stars and revealing previously unseen details of our home Galaxy.

There is hardly a branch of astrophysics which will not be revolutionised by Gaia data.

Gerry Gilmore

Gaia: ̽��ֱ��Galactic Census Takes Shape

ESA/Gaia/DPAC

Gaia’s sky in colour – equirectangular projection

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

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Gaia results revealed – first data release from the most detailed map ever made of the sky

sc604 — Wed, 14 Sep 2016 11:51:09 +0000

Detailed information about more than a billion stars in the Milky Way has been published in the first data release from the Gaia satellite, which is conducting the first-ever ‘galactic census.’ ̽��ֱ��release marks the first chance astronomers and the public have had to get their hands on the most detailed map ever made of the sky.

Gaia, which orbits the sun at a distance of 1.5 million kilometres from the earth, was launched by the European Space Agency in December 2013 with the aim of observing a billion stars and revolutionising our understanding of the Milky Way. During its expected five-year lifespan, Gaia will observe each of a billion stars about 70 times.

̽��ֱ��unique mission is reliant on the work of Cambridge researchers who collect the vast quantities of data transmitted by Gaia to a data processing centre at the ̽��ֱ��, overseen by a team at the Institute of Astronomy.

“Gaia’s first major data release is both a wonderful achievement in its own right, and a taster of the truly dramatic advances to come in future years,” said Professor Gerry Gilmore from the Institute of Astronomy, who is also the UK Principal Investigator for Gaia. “Several UK teams have leading roles in Gaia’s Data Processing and Analysis efforts, which convert the huge raw data streams from the satellite into the beautiful science-ready information now made available for the global scientific and public communities. UK industry made critical contributions to the Gaia spacecraft. ̽��ֱ��UK public, including school students, as well as scientists, are sharing the excitement of this first ever galactic census.”

In addition to the work taking place at Cambridge, teams from Edinburgh, the Mullard Space Science Laboratory (MSSL) at UCL London, Leicester, Bristol and the Science and Technology Facilities Council’s Rutherford Appleton Lab are all contributing to the processing of the vast amounts of data from Gaia, in collaboration with industrial and academic partners from across Europe.

̽��ֱ��team in Cambridge, led by Dr Floor van Leeuwen, Dr Dafydd Wyn Evans and Dr Francesca De Angeli, processed the flux information – the amount of energy that crosses a unit area per unit time – providing the calibrated magnitudes of around 1.6 billion stars, 1.1 billion of which are now published as part of the first data release.

̽��ֱ��Cambridge team also check the daily photometric data for unexpected large outliers, which led to the regular publication of photometric science alerts that were ready for immediate follow-up observations from the ground.

“ ̽��ֱ��sheer volume of data processed for this first release is beyond imagination: around 120 billion images were analysed, and most of these more than once, as all the processing is iterative,” said van Leeuwen, who is Gaia photometric data processing lead. “Many problems had to be overcome, and a few small ones still remain. Calibrations have not yet reached their full potential. Nevertheless, we are already reaching accuracies that are significantly better than expected before the mission, and which can challenge most ground-based photometric data in accuracy.”

“This first Gaia data release has been an important exercise for the Gaia data reduction teams, getting them to focus on deliverable products and their description,” said Evans. “But it is only the first small step towards much more substantial results.”

While today marks the first major data release from Gaia, in the two years since its launch, the satellite has been producing scientific results in the form of Gaia Alerts.

Dr Simon Hodgkin, lead of the Cambridge Alerts team said, “ ̽��ֱ��Gaia Alerts project takes advantage of the fact that the Gaia satellite scans each part of the sky repeatedly throughout the mission. By comparing successive observations of the same patch of sky, scientists can search for transients – astronomical objects which brighten, fade, change or move. These transients are then announced to the world each day as Gaia Alerts for both professional and amateur astronomers to observe with telescopes from the ground.”

̽��ֱ��range of Gaia’s discoveries from Science Alerts is large – supernovae of various types, cataclysmic variable stars, novae, flaring stars, gravitational microlensing events, active galactic nuclei and quasars, and many sources whose nature remains a mystery.

Gaia has discovered many supernovae, the brilliant explosions of stars at the end of their lives. Many of these have been ‘Type Ia’ supernovae, which can be used to measure the accelerating expansion of the Universe. But among these apparently typical supernovae there have been some rarer events. Gaia16ada was spotted by Gaia in the nearby galaxy NGC4559, and appears to be an eruption of a very massive, unstable star. ̽��ֱ��Hubble Space Telescope observed this galaxy some years ago, allowing astronomers to pinpoint the precise star which erupted.

Another lucky catch for Gaia was the discovery of Gaia16apd – a supernova which is nearly a hundred times brighter than normal. Astronomers still don't know what the missing ingredient in these ultra-bright supernovae is, and candidates include exotic rapidly spinning neutron stars, or jets from a black hole. Cambridge astronomer Dr Morgan Fraser is trying to understand these events, saying, “We have only found a handful of these exceptionally bright supernovae, compared to thousands of normal supernovae. For Gaia to spot one so nearby is a fantastic result.”

Many of the Gaia Alerts found so far are bright enough to be observable with a small telescope. Amateur astronomers have taken images of supernovae found by Gaia, while schoolchildren have used robotic telescopes including the Faulkes Telescopes in Australia and Hawaii to do real science with transients.

Dr Hodgkin said: “Since the announcement of the first transients discovered with Gaia in September 2014, over one thousand alerts have been released. With Gaia continually relaying new observations to ground, and our team working on finding transients continually improving their software, the discoveries look set to continue well into the future!”

For the UK teams the future means providing improvements in the pre-processing of the data and extending the processing to cover the photometric Blue and Red prism data. Also data from the Radial Velocity Spectrometer, with major involvement from MSSL, will be included in future releases. ̽��ֱ��photometric science alerts will continue to operate throughout the mission, and summaries of the results will be included in future releases. “Despite the considerable amount of data, the first Gaia data release provides just a taste of the accuracy and completeness of the final catalogue,” said De Angeli.

̽��ֱ��Cambridge Gaia team has also released a dedicated smartphone app, which will allow anyone worldwide to follow the Gaia Alerts discoveries as they happen. Real spacecraft data will be available to the world as soon as it is processed, with users able to follow the discoveries and see what they are. Information to access the app is available at https://gaia.ac.uk.

̽��ֱ��Gaia data processing teams in the UK have been and are being supported by the UK Space Agency and the STFC. STFC helped the set-up of the data applications centre and STFC’s current support involves the UK exploitation of the scientific data to be yielded from the mission. Industrial partners include Airbus, MSSL and e2v Technologies.

̽��ֱ��first results from the Gaia satellite, which is completing an unprecedented census of more than one billion stars in the Milky Way, are being released today to astronomers and the public.

Gaia’s first major data release is both a wonderful achievement in its own right, and a taster of the truly dramatic advances to come in future years.

Gerry Gilmore

ESA/Gaia/DPAC

Gaia’s first sky map

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

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