̽��ֱ�� of Cambridge - European Space Agency (ESA)

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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Galactic ‘vapour trails’ uncovered in giant cluster

fpjl2 — Fri, 20 Sep 2013 09:44:57 +0000

Unusual gas filament ‘arms’ have been found in the central region of the Coma cluster, a large collection of thousands of galaxies located about 300 million light years from Earth - and one of the largest structures in the Universe held together by gravity.

These remarkably long arms – which bear resemblance to vast galactic vapour trails - glow in X-ray light, and tell astronomers about the collisions that took place between Coma and other galaxy clusters over the last billion years.

A team of astronomers from Cambridge and the Max Planck Institute discovered the enormous X-ray vapour trails – spanning at least half a million light years – in Coma by using data from NASA’s Chandra X-ray Observatory as well as ESA’s XMM-Newton. ̽��ֱ��elongated filaments of hot gas were revealed after enhancing the detail in Chandra X-ray images, shown in purple above.

Researchers think that these arms were most likely formed when smaller galaxy clusters had their hot gas stripped away while merging with the larger Coma cluster. This would have left a trail of superheated gas behind them similar to a jet leaving behind trails of water vapour as it moves across the sky.

Coma is an unusual galaxy cluster because it contains not one, but two giant elliptical galaxies near its centre. These two giant elliptical galaxies are probably the trace remains of each of the two largest galaxies that merged with Coma in the past. There are also other signs of past collisions and mergers that the researchers were able to uncover in the data.

̽��ֱ��newly discovered X-ray arms are thought to be about 300 million years old, and they appear to have a rather smooth shape. This gives researchers some clues about the conditions of the hot gas in Coma. Most theoretical models expect that mergers between clusters like those in Coma will produce strong turbulence, like ocean water that has been churned by passing ships. Instead, the smooth shape of these lengthy arms points to a rather calm setting for the hot gas in the Coma cluster, even after many mergers.

“Coma is like a giant cosmic train wreck where several clusters have collided with each other. We hadn’t expected that these rather delicate straight filaments would survive in that environment,” said lead author Dr Jeremy Sanders, who conducted much of the research whilst at Cambridge’s Institute of Astronomy alongside Professor Andrew Fabian.

“ ̽��ֱ��existence of these long straight structures appears to point towards the centre of the Coma cluster being a much calmer environment than we had expected.”

Elongated structures of hot gas found after enhancing the detail in images taken with the Chandra (pink) and on larger scales XMM-Newton (purple) X-ray observatories

Two of the arms appear to be connected to a group of galaxies located about two million light years from the centre of Coma. One or both of the arms connects to a larger structure seen in the XMM-Newton data, and spans a distance of at least 1.5 million light years. A very thin tail also appears behind one of the galaxies in Coma. This is probably evidence of gas being stripped from a single galaxy, in addition to the groups or clusters that have merged there.

Galaxy clusters are the largest objects held together by gravity in the universe. ̽��ֱ��collisions and mergers between galaxy clusters of similar mass are the most energetic events in the nearby universe. These new results are important for understanding the physics of these enormous objects and how they grow.

Large-scale magnetic fields are likely responsible for the small amount of turbulence that is present in Coma. Estimating the amount of turbulence in a galaxy cluster has been a challenging problem for astrophysicists. Researchers have found a range of answers, some of them conflicting, and so observations of other clusters are needed.

These new results on the Coma cluster, which incorporate over six days worth of Chandra observing time, appears in the latest issue of the journal Science.

Text adapted from a NASA Chandra press release

Astronomers have discovered enormous smooth shapes that look like vapour trails in a gigantic galaxy cluster. These ‘arms’ span half a million light years and provide researchers with clues to a billion years of collisions within the “giant cosmic train wreck” of the Coma cluster.

Coma is like a giant cosmic train wreck where several clusters have collided with each other. We hadn’t expected that these rather delicate straight filaments would survive in that environment

Jeremy Sanders

NASA Chandra

Revealed elongated filaments of hot gas found after enhancing the detail in Chandra X-ray images (purple), also showing the optical light galaxies in cluster (taken from the Sloan Digital Sky Survey)

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Twinkle, twinkle, little star: I’m going to know what you are

ns480 — Thu, 26 Apr 2012 08:30:37 +0000

A powerful data centre being turned on today at the Institute for Astronomy (IoA) will process the vast amount of imaging data sent back to Earth by a satellite which is due to be launched into space in August 2013. ̽��ֱ��Gaia satellite, whose heart is the largest digital camera ever built, will orbit the Sun at a distance of 1.5 million km from Earth and will feed the data centre with a billion-pixel video of a billion stars, galaxies, quasars and solar system asteroids for five years after launch.

̽��ֱ��installation of the data centre, funded by the UK Space Agency, coincides with the 50th Anniversary of the launch of the British satellite research programme, Ariel-1, which was devoted to studying the ionosphere - a part of the upper atmosphere.

̽��ֱ��Gaia satellite, which has been hailed as the premier European astrophysics space mission of the decade, will deliver an extraordinarily precise census of the Milky Way in three dimensions.

“As Gaia slowly spins, it will create a billion-pixel video of the Milky Way, watching everything move, and deducing what is there, and where it is,” explained Professor Gerry Gilmore, from the IoA and the UK Principal Investigator for UK involvement in the mission. “On its five-year mission, Gaia will produce a vast amount of information - almost inconceivable in its scope.”

In 1989, the European Space Agency (ESA) launched Hipparcos, the first –and so far the only - satellite to chart the positions of stars, which produced a primary catalogue of about 118,000 stars, followed by a secondary catalogue, called Tycho, of over 2 million stars.

Technology has improved to such an extent since Hipparcos was launched that Gaia will be able to measure a star’s position and motion 200 times more accurately, and will measure one billion stars.

In order to process Gaia's photometric data, the team has worked for several years to develop a system that can calibrate the 'raw' transmitted photometric data. Even highly compressed, the data transmitted by the satellite over the five-year mission would fill over 30,000 CDROMs (1300 DVDs). Many times that amount will be produced during the processing of the data as intermediate results of computations.

̽��ֱ��new installation consists of a cluster of 108 identical servers used for the bulk of the data processing, and 9 additional servers used for monitoring, backup and control. ̽��ֱ��108 processing servers each have 2 6-core CPUs, 48 gigabytes of RAM and 9 terabytes (a terabyte is 1000 gigabytes) of hard-disk storage. Therefore the bulk processing system as a whole has 1296 processing cores, around 5 terabytes of RAM and nearly 1 petabyte (1000 terabytes) of hard-disk storage for use during the active processing. ̽��ֱ��individual servers are connected by a high-speed 40 gigabit Infiniband network to allow rapid communication and transfers of large data volumes.

̽��ֱ��system will process the photometric data from Gaia during the 5-6 years of mission operation, and for two years afterwards, to produce a calibrated set of measurements which can be freely used by the astronomical community.

Dr Floor van Leeuwen, from the IoA, is project manager and coordinator of the consortium that will process the Gaia photometric data, which involves 60 scientists across Europe, of the 400 in total in the Gaia project. “We installed our major computer processing capability, and now are very busy bring together the huge processing effort which will use this impressive hardware system to turn images into science. We need to be ready for Gaia’s launch, just next year After so many years preparation, this is excitingly, but challengingly, soon.” he said.

Gaia is one of the most important current space projects for the UK, which has won approximately €80 million of contracts from ESA to build parts of the spacecraft.

Remarkably, its two optical telescopes are capable of measuring the positions of celestial objects to an accuracy of up to 10 microarcseconds, comparable to the diameter of a human hair at a distance of 1000 km. To determine the properties of stars, Gaia will also split their emitted light into a spectrum before communicating the data back to Earth.

After launch, a 10 m diameter ‘skirt’ will unfold around the satellite to shade the telescopes and generate its own energy from solar panels.

Gaia is expected to discover a multitude of new objects both in our solar system - including brown dwarfs and white dwarfs, supernovae and extra-solar planets - as well probe the distribution of dark matter , map over 500,000 quasars in the Universe, and measure the local structure of space-time.

Added Gilmore: “By creating the first precise 3-D chart of our galaxy, Gaia will help scientists understand the enormous range of complexities related to the origin, structure and evolution of our Milky Way, the past history of the Sun’s location in the Milky Way, and the time and place where the chemical elements of which we are made were created, as well as discover new objects, from potentially killer asteroids to explosions in the distant Universe.”

A team of astronomers at the ̽��ֱ�� of Cambridge is taking the next big step in a European-wide programme which will lead to the creation of the first three-dimensional map of more than a billion stars.

As Gaia slowly spins, it will create a billion-pixel video of the Milky Way, watching everything move, and deducing what is there, and where it is.

Professor Gerry Gilmore

European Space Agency

Gaia Deployable Sunshield Assembly

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