User manual Gaia spacecraft
For over four years, the Milky Way mapper pinpointed over a billion stars to create an expansive dataset
Latest research and how the Milky Way mapper works
This almost sombrero-shaped spacecraft has been mapping the stars for more than four years. Its recent data release contains unrivalled information on nearly 1.7 billion stars, and is to date the greatest catalogue of stars ever produced. The European Space Agency (ESA) initially had the idea of using Gaia as an optical interferometer mission, meaning that Gaia originally would have been a series of smaller telescopes working together to create an image similar to that from a larger telescope.
Thus ESA gave the mission its original name: the Global Astrometric Interferometer for Astrophysics, or GAIA. After the mission evolved and the interferometer idea was dropped, the name stuck. However, the previous design was altered and Gaia's primary objective would be to create the largest, most precise three-dimensional map of the stars in our galaxy within its intended five-year mission, building on the legacy of their Hipparcos mission.
The name change wasn’t the only aspect that changed plans for Gaia, as too was its launch, originally scheduled for December 2011. After a series of complications to Gaia and the liftoff schedule the spacecraft finally left Earth two years behind schedule, riding aboard a Soyuz-Fregat rocket. With a launch mass of 2,030 kilograms (4,475
Gaia will not only map the stars within our galaxy, but will provide
more insight into the galaxy’s composition, formation and evolution pounds),
Gaia was sent on its way to its new home at Lagrange point 2 (L2) roughly 1.5 million kilometres (932,057 miles) away from Earth. This is an ideal location to observe the wider universe, and a cosmic ‘parking spot’ which relies on the gravity of the Sun and Earth to keep the space observatory fixed in this one spot. While at L2 Gaia is in a Lissajous-type orbit that has a period of about 180 days around a fixed point at L2.
Before Gaia could examine the sky properly there were some hiccups. The Gaia team needed to sort out issues with the optics, including some areas of water freezing and ‘stray light’, where some of the Sun’s light was making its way into Gaia’s focal plane. On 25 July 2014, Gaia officially began its science mission and could start scanning the sky. On average, Gaia observes each single star, of the intended billion stars, 70 times over the course of its five years. Sweeping the skies once every six hours, the two onboard telescopes focus the light that is measured by three major instruments fixed on the same focal plane. The focal plane can be thought of as the largest space camera ever created, consisting
of 106 CCDs and equating to an enormous 1 billion pixels. The first instrument, the astrometric instrument (Astro), is devoted to measuring a star’s position, proper motion and parallax (therefore its distance). The second, the photometric instrument (BP/RP), consists of a blue and a red photometer, and they provide information about a star’s temperature, mass and chemical composition. Lastly, the third instrument, which is the RadialVelocity Spectrometer (RVS), measures how fast a subset of stars are moving relative to Gaia.
Throughout the years Gaia has not experienced many other hiccups, and has proven successful in its quest for stellar knowledge. This is shown in its two major data releases, the first of which came out on 14 September 2016 and the second more recently on 25 April 2018. The first release detailed the precise position and brightness of over 1.1 billion stars, which at the time was the most detailed 3D map ever created.
After a period of 22 months of data collection, a second catalogue was released and scientists marvelled at the results; the position and brightness of 1,692,919,135 stars was found! For some of the brightest stars in this survey, the level of precision was so good that it would be similar to an observer on Earth being able to locate a pound coin lying on