̽��ֱ�� of Cambridge - Gerry Gilmore

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: scientists take a step closer to revealing origins of our galaxy

sc604 — Thu, 03 Dec 2020 12:09:57 +0000

̽��ֱ��measurements of stellar positions, movement, brightness and colours are in the third early data release from the European Space Agency’s Gaia space observatory, and are now publicly available. Initial findings include the first optical measurement of the acceleration of the Solar system.

Launched in 2013, Gaia operates in an orbit around the so-called Lagrange 2 (L2) point, located 1.5 million kilometres behind the Earth in the direction away from the Sun. At L2 the gravitational forces between the Earth and Sun are balanced, so the spacecraft stays in stable position, allowing long-term essentially unobstructed views of the sky.

̽��ֱ��primary objective of Gaia is to measure stellar distances using the parallax method. In this case astronomers use the observatory to continuously scan the sky, measuring the apparent change in the positions of stars over time, resulting from the Earth’s movement around the Sun.

Knowing that tiny shift in the positions of stars allows their distances to be calculated. On Earth this is made more difficult by the blurring of the Earth’s atmosphere, but in space the measurements are only limited by the optics of the telescope.

Two previous releases included the positions of 1.6 billion stars. Today’s release brings the total to just under 2 billion stars, whose positions are significantly more accurate than in the earlier data. Gaia also tracks the changing brightness and the positions of the stars over time across the line of sight (their so-called proper motion), and by splitting their light into spectra, measures how fast they are moving towards or away from the Sun and assesses their chemical composition.

̽��ֱ��new data include exceptionally accurate measurements of the 300,000 stars within the closest 326 light years to the Sun. ̽��ֱ��researchers use these data to predict how the star background will change in the next 1.6 million years. They also confirm that the Solar system is accelerating in its orbit around the Galaxy.

This acceleration is gentle, and is what would be expected from a system in a circular orbit. Over a year the Sun accelerates towards the centre of the Galaxy by 7 mm per second, compared with its speed along its orbit of about 230 kilometres a second.

Gaia data additionally deconstruct the two largest companion galaxies to the Milky Way, the Small and Large Magellanic Clouds, allowing researchers to see their different stellar populations. A dramatic visualisation shows these subsets, and the bridge of stars between the two systems.

Dr Floor van Leeuwen of Cambridge’s Institute of Astronomy said: “Gaia is measuring the distances of hundreds of millions of objects that are many thousands of light years away, at an accuracy equivalent to measuring the thickness of hair at a distance of more than 2000 kilometres. These data are one of the backbones of astrophysics, allowing us to forensically analyse our stellar neighbourhood, and tackle crucial questions about the origin and future of our Galaxy.”

Gaia will continue gathering data until at least 2022, with a possible mission extension until 2025. ̽��ֱ��final data releases are expected to yield stellar positions 1.9 times as accurate as those released so far, and proper motions more than 7 times more accurate, in a catalogue of more than two billion objects.

“ ̽��ֱ��mysteries of the Milky Way and our Solar System have captured the imagination of generations of scientists and astronomers across the world – all eager to learn more about the origins of the Universe,” said Science Minister Amanda Solloway. “Through this remarkable government-backed mission, UK scientists have taken us a giant leap closer to advancing our knowledge of how our Solar System began by painting the most detailed picture yet that could help to redefine astronomy as we know it.”

Adapted from a Royal Astronomical Society press release.

An international team of astronomers, led by the ̽��ֱ�� of Cambridge, announced the most detailed ever catalogue of the stars in a huge swathe of our Milky Way galaxy.

Gaia is measuring the distances of hundreds of millions of objects that are many thousands of light years away, at an accuracy equivalent to measuring the thickness of hair at a distance of more than 2000 kilometres

Floor van Leeuwen

ESA/Gaia/DPAC; Acknowledgement: A. Moitinho.

̽��ֱ��colour of the sky from Gaia’s Early Data Release 3

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 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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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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Vice-Chancellor says staying in the European Union is vital to maintain the UK’s role in world-leading research

pbh25 — Fri, 25 Sep 2015 08:51:16 +0000

Remaining in the European Union will allow the UK to continue its globally recognised research and tackle the most important challenges facing the world said the Vice-Chancellor of the ̽��ֱ�� of Cambridge yesterday (25 Sept, 2015).

Professor Sir Leszek Borysiewicz warned in a keynote speech that the UK could lose its position as a leading light in European research and find itself on the fringes trying to “pick up the scraps”, if the UK pulled out of the EU.

Speaking at ‘Excellent research in the UK: Do we need the EU?’ the Vice-Chancellor said that 17 per cent of last year’s research income at the ̽��ֱ��, totalling £68 million, had come from the EU’s Horizon 2020 scheme– but he stressed that the importance of the Union went beyond its monetary value to UK institutions.

He said: “Even more than the funding, it is society, and society’s needs, that are the drivers that keep us going forward. In today’s competitive world we cannot stand alone.”

His speech came at the start of the event which was organised by the European Parliament Information Office, the International Unit of Universities UK, and the ̽��ֱ�� of Cambridge.

̽��ֱ��Vice-Chancellor said European collaborations drove the ̽��ֱ��’s fundamental purpose – to serve society through teaching, research and learning at the highest international standards of excellence.

He added: “Under Horizon 2020 we did something that was special. Europe made a statement to the whole world that it is going to be tackling global problems which are not just of petty interest in Cambridge, or East Anglia, or in the United Kingdom, but ones that will make a difference to the world – the world I am going to leave behind for my granddaughters.”

He added that issues like cancer, climate change and aging required research without boundaries, allowing free movement and collaboration between academics.

As an example he cited InnoLife Knowledge and Innovation Community, a €2.1bn project launched last year, supported by the European Institute of Innovation and Technology, to address the impact of ageing populations and dependence. It involves 144 European companies, research institutions and universities across nine EU countries, including the ̽��ֱ�� of Cambridge.

“That scale is exactly what is needed if we are to overcome society’s grand challenges. Put simply, we cannot access the talent, develop the infrastructure or provide the funding at a national level.”

Being inside Europe allowed the UK to help shape policy said the Chancellor, adding: “I’d rather we stay in the boat, trying to shape and to lead research policy in Europe, than to stay on the side-lines picking up scraps.”

̽��ֱ��event also featured talks from ̽��ֱ�� of East Anglia Vice-Chancellor Professor David Richardson, MEP Vicky Ford, and Professors Gerry Gilmore and Florin Udrea of the ̽��ֱ�� of Cambridge. A panel discussion was also held, led by BBC presenter Martine Croxall.

‘Excellent research in the UK: Do we need the EU?’ event held at Downing College, Cambridge

In today’s competitive world we cannot stand alone.

Vice-Chancellor Professor Sir Leszek Borysiewicz

Cédric Puisney

Parlamentarium Bruxelles

̽��ֱ��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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Using stellar ‘twins’ to reach the outer limits of the galaxy

sc604 — Thu, 03 Sep 2015 23:33:20 +0000

Astronomers from the ̽��ֱ�� of Cambridge have developed a new, highly accurate method of measuring the distances between stars, which could be used to measure the size of the galaxy, enabling greater understanding of how it evolved.

Using a technique which searches out stellar ‘twins’, the researchers have been able to measure distances between stars with far greater precision than is possible using typical model-dependent methods. ̽��ֱ��technique could be a valuable complement to the Gaia satellite – which is creating a three-dimensional map of the sky over five years – and could aid in the understanding of fundamental astrophysical processes at work in the furthest reaches of our galaxy. Details of the new technique are published in the Monthly Notices of the Royal Astronomical Society.

“Determining distances is a key problem in astronomy, because unless we know how far away a star or group of stars is, it is impossible to know the size of the galaxy or understand how it formed and evolved,” said Dr Paula Jofre Pfeil of Cambridge’s Institute of Astronomy, the paper’s lead author. “Every time we make an accurate distance measurement, we take another step on the cosmic distance ladder.”

̽��ֱ��best way to directly measure a star’s distance is by an effect known as parallax, which is the apparent displacement of an object when viewed along two different lines of sight – for example, if you hold out your hand in front of you and look at it with your left eye closed and then with your right eye closed, your hand will appear to move against the background. ̽��ֱ��same effect can be used to calculate the distance to stars, by measuring the apparent motion of a nearby star compared to more distant background stars. By measuring the angle of inclination between the two observations, astronomers can use the parallax to determine the distance to a particular star.

However, the parallax method can only be applied for stars which are reasonably close to us, since beyond distances of 1600 light years, the angles of inclination are too small to be measured by the Hipparcos satellite, a precursor to Gaia. Consequently, of the 100 billion stars in the Milky Way, we have accurate measurements for just 100,000.

Gaia will be able to measure the angles of inclination with far greater precision than ever before, for stars up to 30,000 light years away. Scientists will soon have precise distance measurements for the one billion stars that Gaia is mapping – but that’s still only one percent of the stars in the Milky Way.

For even more distant stars, astronomers will still need to rely on models which look at a star’s temperature, surface gravity and chemical composition, and use the information from the resulting spectrum, together with an evolutionary model, to infer its intrinsic brightness and to determine its distance. However, these models can be off by as much as 30 percent. “Using a model also means using a number of simplifying assumptions – like for example assuming stars don’t rotate, which of course they do,” said Dr Thomas Mädler, one of the study’s co-authors. “Therefore stellar distances obtained by such indirect methods should be taken with a pinch of salt.”

̽��ֱ��Cambridge researchers have developed a novel method to determine distances between stars by relying on stellar ‘twins’: two stars with identical spectra. Using a set of around 600 stars for which high-resolution spectra are available, the researchers found 175 pairs of twins. For each set of twins, a parallax measurement was available for one of the stars.

̽��ֱ��researchers found that the difference of the distances of the twin stars is directly related to the difference in their apparent brightness in the sky, meaning that distances can be accurately measured without having to rely on models. Their method showed just an eight percent difference with known parallax measurements, and the accuracy does not decrease when measuring more distant stars.

“It’s a remarkably simple idea – so simple that it’s hard to believe no one thought of it before,” said Jofre Pfeil. “ ̽��ֱ��further away a star is, the fainter it appears in the sky, and so if two stars have identical spectra, we can use the difference in brightness to calculate the distance.”

Since a utilised spectrum for a single star contains as many as 280,000 data points, comparing entire spectra for different stars would be both time and data-consuming, so the researchers chose just 400 spectral lines to make their comparisons. These particular lines are those which give the most distinguishing information about the star – similar to comparing photographs of individuals and looking at a single defining characteristic to tell them apart.

̽��ֱ��next step for the researchers is to compile a ‘catalogue’ of stars for which accurate distances are available, and then search for twins among other stellar catalogues for which no distances are available. While only looking at stars which have twins restricts the method somewhat, thanks to the new generation of high-powered telescopes, high-resolution spectra are available for millions of stars. With even more powerful telescopes under development, spectra may soon be available for stars which are beyond even the reach of Gaia, so the researchers say their method is a powerful complement to Gaia.

“This method provides a robust way to extend the crucially-important cosmic distance ladder in a new special way,” said Professor Gerry Gilmore, the Principal Investigator for UK involvement in the Gaia mission. “It has the promise to become extremely important as new very large telescopes are under construction, allowing the necessary detailed observations of stars at large distances in galaxies far from our Milky Way, building on our local detailed studies from Gaia.”

̽��ֱ��research was funded by the European Research Council.

Reference:
Jofré, P. et. al. Climbing the cosmic ladder with stellar twins. Monthly Notices of the Royal Astronomical Society (2015). DOI: 10.1093/mnras/stv1724.

A new method of measuring the distances between stars enables astronomers to climb the ‘cosmic ladder’ and understand the processes at work in the outer reaches of the galaxy.

Determining distances is a key problem in astronomy, because unless we know how far away a star or group of stars is, it is impossible to know the size of the galaxy or understand how it formed and evolved

Paula Jofre Pfeil

Carolina Jofré

Two ‘twin’ stars with identical spectra observed by the La Silla Telescope. Since it is known that one star is 40 parsecs away, the difference in their apparent brightnesses allows calculation of the second star’s distance

̽��ֱ��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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One year and 272 billion measurements later, Gaia team celebrates first anniversary of observations

sjr81 — Tue, 25 Aug 2015 16:06:41 +0000

̽��ֱ��Gaia satellite, which orbits the sun at a distance of 1.5million km 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.

̽��ֱ��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 university, overseen by a team at the Institute of Astronomy.

Since the start of its observations in August 2014, Gaia has recorded 272 billion positional (or astrometric) measurements and 54.4 billion brightness (or photometric) data points.

Gaia surveys stars and many other astronomical objects as it spins, observing circular swathes of the sky. By repeatedly measuring the positions of the stars with extraordinary accuracy, Gaia can tease out their distances and motions throughout the Milky Way galaxy.

Dr Francesca de Angeli, lead scientist at the Cambridge data centre, said: “ ̽��ֱ��huge Gaia photometric data flow is being processed successfully into scientific information at our processing centre and has already led to many exciting discoveries.”

̽��ֱ��Gaia team have spent a busy year processing and analysing data, with the aim of developing enormous public catalogues of the positions, distances, motions and other properties of more than a billion stars. Because of the immense volumes of data and their complex nature, this requires a huge effort from expert scientists and software developers distributed across Europe, combined in Gaia’s Data Processing and Analysis Consortium (DPAC).

“ ̽��ֱ��past twelve months have been very intense, but we are getting to grips with the data, and are looking forward to the next four years of operations,” said Timo Prusti, Gaia project scientist at ESA.

“We are just a year away from Gaia's first scheduled data release, an intermediate catalogue planned for the summer of 2016. With the first year of data in our hands, we are now halfway to this milestone, and we’re able to present a few preliminary snapshots to show that the spacecraft is working well and that the data processing is on the right track.”

As Gaia has been conducting its repeated scans of the sky to measure the motions of stars, it has also been able to detect whether any of them have changed their brightness, and in doing so, has started to discover some very interesting astronomical objects.

Gaia has detected hundreds of transient sources so far, with a supernova being the very first on August 30, 2014. These detections are routinely shared with the community at large as soon as they are spotted in the form of ‘Science Alerts’, enabling rapid follow-up observations to be made using ground-based telescopes in order to determine their nature.

One transient source was seen undergoing a sudden and dramatic outburst that increased its brightness by a factor of five. It turned out that Gaia had discovered a so-called ‘cataclysmic variable’, a system of two stars in which one, a hot white dwarf, is devouring mass from a normal stellar companion, leading to outbursts of light as the material is swallowed. ̽��ֱ��system also turned out to be an eclipsing binary, in which the relatively larger normal star passes directly in front of the smaller, but brighter white dwarf, periodically obscuring the latter from view as seen from Earth.

Unusually, both stars in this system seem to have plenty of helium and little hydrogen. Gaia’s discovery data and follow-up observations may help astronomers to understand how the two stars lost their hydrogen.

Gaia has also discovered a multitude of stars whose brightness undergoes more regular changes over time. Many of these discoveries were made between July and August 2014, as Gaia performed many subsequent observations of a few patches of the sky.

Closer to home, Gaia has detected a wealth of asteroids, the small rocky bodies that populate our solar system, mainly between the orbits of Mars and Jupiter. Because they are relatively nearby and orbiting the Sun, asteroids appear to move against the stars in astronomical images, appearing in one snapshot of a given field, but not in images of the same field taken at later times.

Gaia scientists have developed special software to look for these ‘outliers’, matching them with the orbits of known asteroids in order to remove them from the data being used to study stars. But in turn, this information will be used to characterise known asteroids and to discover thousands of new ones.

Gerry Gilmore, Professor of Experimental Philosophy, and the Gaia UK Principal Investigator, said: “ ̽��ֱ��early science from Gaia is already supporting major education activity involving UK school children and amateur astronomers across Europe and has established the huge discovery potential of Gaia’s data.

"We are entering a new era of big-data astrophysics, with a revolution in our knowledge of what we see in the sky. We are moving beyond just seeing to knowing about the galaxy in which we live.”

A space mission to create the largest, most-accurate, three-dimensional map of the Milky Way is celebrating its first completed year of observations.

We are moving beyond just seeing to knowing about the galaxy in which we live.

Gerry Gilmore

Gaia's mission: solving the celestial puzzle

Credit: Marisa Grove/Institute of Astronomy

Artist’s impression of Gaia14aae

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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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