ESA's Gaia celebrates its first year observing

The observatory will monitor a billion stars over five years. Already the mission has detected supernovae, extreme binary systems and taken over two million parallax measurements. 

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The mission has also discovered hundreds of asteroids within our own Solar System.
Credit: ESA/ATG medialab; background: ESO/S. Brunier

ESA’s Gaia satellite celebrates its first year of observing one billion stars. Over the next four years the mission will continue to watch the skies, imaging each star at least 70 times to precisely measure its size, position, distance, movement and brightness.

The telescope launched on 19 December 2013, beginning its operation six months later. On 30 August 2014, the satellite made its a big discovery when it located its first supernova. A year later, Gaia has already recorded 272 billion positional measurements, 54.4 billion brightness measurements and taken 5.4 billion spectra. However, processing this huge amount of data takes some time and effort.

"The 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 nominal operations," says Timo Prusti, Gaia project scientist at ESA.

Despite the huge task, some snapshots of the data are beginning to emerge. The team at ESA have already managed to provide parallax measurements for two million stars. Parallax is a method for determining distances by seeing how much a nearby star appears to shift against background stars. The greater the shift, the nearer the star. Gaia will provide more parallax distance measurements for stars than any mission before it.

By monitoring such a huge number of stars the mission also hopes to catch transient events and has discovered hundreds so far. Often these are variable stars or supernovae but sometimes they are more dramatic, such as the ‘cataclysmic variable’ star – a hot white dwarf which is devouring mass from a normal stellar companion, generating outbursts of light. As soon as one of these special events occurs, the team send out a Science Alert allowing follow up observations to happen as soon as possible.

Though the mission will not be over for another four years, the team at ESA hope to release an intermediate catalogue of the data to researchers in mid 2016.

“These early proof-of-concept studies demonstrate the quality of the data collected with Gaia so far and the capabilities of the processing pipeline,” says Prusti. “The final data products are not quite ready yet, but we are working hard to provide the first of them to the community next year. Watch this space.”


 

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