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Esa has unveiled a stunning 3D map of a billion stars in our galaxy that is 1,000 times more complete than anything that previously existed.

The data for the map was collected by a space-based probe called Gaia, which has been circling the sun nearly a million miles beyond Earth's orbit since its launch in December 2013.

On its journey, the satellite has been discreetly snapping pictures of the Milky Way.

Now the European Space Agency has released the first batch of data collected by Gaia, which includes information on the brightness and position of over a billion stars.

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The European Space Agency has released the first batch of data collected by Gaia, which includes information on the brightness and position of over a billion stars. An all-sky view of stars in our galaxy and neighbouring galaxies is pictured, based on the first year of observations from ESA’s Gaia satellite, from July 2014 to September 2015

The satellite is now just over half-way through its five-year mission, and Gaia's two telescopes have located a billion stars.

This sounds like a lot, but is still only one per cent of the Milky Way's estimated stellar population, that lies scattered over an area 100,000 light years in diameter. 

'The beautiful map we are publishing today shows the density of stars measured by Gaia across the entire sky, and confirms that it collected superb data during its first year of operations,' said Timo Prusti, a Gaia project scientist at ESA.

The satellite's billion-pixel camera, the largest ever in space, is so powerful it would be able to gauge the diameter of a human hair at a distance of 621 miles (1,000 km).

This means nearby stars have been located with unprecedented accuracy.

'Over the centuries we have sought to catalogue the content of the skies,' said Francois Mignard, an astronomer at France's National Centre for Scientific Research and a member of the Gaia science team.

'But never have we achieved anything so complete or precise—it is a massive undertaking.'

This first data dump 'opens a new chapter in astronomy,' he added, and is certain to generate hundreds of scientific studies.

Gaia's mapping effort is already unprecedented in scale, but it still has several years left to run.

Gaia maps the position of the Milky Way's stars in a couple of ways.

It pinpoints the location of the stars but the probe can also plot their movement, by scanning each star about 70 times.

This is what allows scientists to calculate the distance between Earth and each star, which is a crucial measure.

While the location of 1 billion stars has been measured, the distance to only 2 million stars is available.

'That's 20 times more than what we had before,' Mignard said. 'And all in one fell swoop!'

By the end of 2017, Gaia will have done the same for a billion stars.

At the same time as plotting distances from Earth, the satellite will collect vital data about each star's temperature, luminosity and chemical composition.

A space-based probe called Gaia has been circling the sun nearly a million miles beyond Earth's orbit since its launch in December 2013. On its journey, the satellite has been discreetly snapping pictures of the Milky Way. Now the first batch of data collected by Gaia hsa been published, including information on the brightness and position of over a billion stars

Artist's impression of Gaia mapping the stars of the Milky Way. Gaia's mapping effort is already unprecedented in scale, but it still has several years left to run. Gaia maps the position of the Milky Way's stars in a couple of ways. It pinpoints the location of the stars but the probe can also plot their movement, by scanning each star about 70 times

On top of plotting stars, tens of thousands of previously undetected objects will be discovered by Gaia over the next five years.

These include asteroids that may one day threaten Earth, planets circling nearby stars, and exploding supernovas.

'It seems like a good bet that the mission will reveal thousands of new worlds,' Gregory Laughlin, an astronomer at Yale University, told Nature.

Astrophysicists hope to learn more about the distribution of dark matter, the invisible substance thought to hold the observable universe together.

They also plan to test Albert Einstein's general theory of relativity by watching how light is deflected by the sun and its planets.

'Gaia is going to revolutionise what we know about stars and the Galaxy,' David Hogg, an astronomer at New York University working on the project told Nature. 

Knowing the positions and motions of stars in the sky to astonishing precision is a fundamental part of studying the properties and past history of the Milky Way and to measure distances to stars and galaxies.

But it also has a variety of applications closer to home – for example, in the solar system.

In July, Pluto passed in front of a distant, faint star, offering a rare chance to study the atmosphere of the dwarf planet as the star gradually disappeared and then reappeared behind Pluto.

Gaia data allowed scientists to predict exactly when this would happen from precise knowledge of the star's position, and allowed astronomers all over the world to witness the event.  

The outline of our Galaxy, the Milky Way, and of its neighbouring Magellanic Clouds, in an image based on housekeeping data from ESA’s Gaia satellite, indicating the total number of stars detected every second in each of the satellite's fields of view. Brighter regions indicate higher concentrations of stars, while darker regions correspond to fewer stars

WHAT GAIA CAN TEACH US ABOUT THE SOLAR SYSTEM: PLUTO'S OCCULATION

The image shows an image of the star and Pluto, five minutes before the event (top), then Pluto passing in front of the star (centre), then again the star and Pluto, five minutes after the event (bottom) 

Knowing the positions and motions of stars in the sky to astonishing precision is a fundamental part of studying the properties and past history of the Milky Way and to measure distances to stars and galaxies.

But it also has a variety of applications closer to home – for example, in the solar system.

In July, Pluto passed in front of a distant, faint star, offering a rare chance to study the atmosphere of the dwarf planet as the star gradually disappeared and then reappeared behind Pluto.

This stellar occultation was visible only from a narrow strip stretching across Europe, similar to the totality path that a solar eclipse lays down on our planet's surface. 

Precise knowledge of the star's position was crucial to point telescopes on Earth, so the exceptional early release of the Gaia position for this star.

This was 10 times more precise than previously available, was instrumental to the successful monitoring of this rare event.

Astronomers observed the event using telescopes across Europe, Middle East and northern Africa. 

To further analyse the data, they were also aided by an improved determination of Pluto’s orbit after Nasa’s New Horizons mission flew by the dwarf planet in 2015.

Early results hint at a pause in the puzzling pressure rise of Pluto's tenuous atmosphere, something that has been recorded since 1988 in spite of the dwarf planet moving away from the sun, which would suggest a drop in pressure due to cooling of the atmosphere.

'These three examples demonstrate how Gaia's present and future data will revolutionise all areas of astronomy, allowing us to investigate our place in the universe, from our local neighbourhood, the solar system, to galactic and even grander, cosmological scales,' said Dr Anthony Brown from Leiden University in the Netherlands.

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This first data release shows the mission is on track to achieve its ultimate goal: charting the positions, distances, and motions of one billion stars – about 1 per cent of the Milky Way's stellar content – in three dimensions to unprecedented accuracy.

'The road to today has not been without obstacles: Gaia encountered a number of technical challenges and it has taken an extensive collaborative effort to learn how to deal with them,' said Fred Jansen, Gaia mission manager at ESA.

'But now, 1000 days after launch and thanks to the great work of everyone involved, we are thrilled to present this first dataset and are looking forward to the next release, which will unleash Gaia's potential to explore our Galaxy as we've never seen it before.'