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Stars and galaxies

Europe prepares to map a billion stars

2 December 2013
The most powerful star mapper ever built will be launched from Europe’s spaceport in French Guiana on 19 December. A Soyuz rocket will send the 2 tonne space observatory, known as Gaia, 1.5 million km from Earth. From there, it will spend the next five years conducting a census of about one billion stars in our Milky Way galaxy.

Gaia will send back the most accurate data ever obtained about the positions, movements and brightness of these stars. Each of the selected stars will be observed about 70 times during the five-year mission. That’s an average of 40 million observations a day! The positions of brighter objects (still 4,000 times fainter than the naked eye can see) will be plotted with an accuracy comparable to measuring the width of a human hair from a distance of 1,000 km.

In order to achieve this remarkable precision, Gaia carries a super-sensitive “eye”, the largest digital camera ever flown in space. This will enable Gaia to detect objects that are a million times fainter than our eyes can see. It also carries two optical telescopes and three scientific instruments, plus a 10 metre wide "skirt" which acts as a sunshield and generates solar power.

Andromeda Galaxy in infrared and X-rays image
Andromeda Galaxy in infrared and X-rays
Gaia’s main task will be to create a 3-D map of the Galaxy. However, it is also expected to discover hundreds of thousands of asteroids and comets in our Solar System; tens of thousands of ‘failed’ stars, called brown dwarfs; 20,000 exploding stars, called supernovas; and hundreds of thousands of active galaxies, called quasars.

Gaia will also discover at least 7,000 planets orbiting distant stars. It will do this by detecting tiny movements in a star’s position as a nearby planet pulls on the star. By the end of the mission, it will have returned 1 Petabyte (1 million Gigabytes) of data, enough to fill 200,000 DVDs.

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