Star by star, Earth’s scientist are gradually unpicking the secrets of the Milky Way galaxy. The latest results from the European Space Agency’s Gaia satellite have helped to produced a three-dimensional map of the our nearest cosmic neighbours containing a mind-blowing 1.7 billion stars.
MOTHER OF ALL SATELLITES
The satellite, named after the Greek Earth mother goddess, is on an ambitious mission to catalogue the stars, planets, comets and asteroids that reside in our galaxy. Its detectors can provide precise positional and velocity measurements, enabling the construction of an accurate 3D representation of the brightest bodies – equating to roughly 1% of the total galactic population.
Launched in 2013, Gaia travelled for three weeks to reach its orbital position around an L2 Lagrange point, 1.5 million km away. Following a period of testing and calibration, Gaia began its mission in July 2014, observing any bright objects between the magnitude ranges of 3 and 20, with 20 being the faintest.
BILLIONS AND BILLIONS
Data from the first 14 months of observations – known as DR1 – was released in September 2016, which included positions and magnitudes for 1.14 billion stars. This was followed in April of 2018 by DR2, which used 22 month’s worth of data, providing the positions and brightness for nearly 1.7 billion stars, up to 8,000 light-years away.
https://youtu.be/8cXURHmtf3IOf those 1.7 billion, 1.3 billion were bright enough to measure distance and motion, while 161 million were bright enough to determine their surface temperature. As a sign of how sensitive Gaia’s instruments are, the degree of precision for brighter objects is equivalent to an Earth-bound observer spotting a Euro coin on the surface of the moon!
Gaia uses three main instrument to carry out its observations: Astro, an astrometry device for measuring position and distance; BP/RP, a photometric system for acquiring luminosity values; and RVS, the Radial-Velocity Spectrometer for determining velocities. The total cost of the Gaia mission is around €470 million – around $1 billion – but its impact on astronomy is beyond measure, with information on variable stars, star clusters, galactic dust, more than 14,000 asteroids within our solar system as well as 500,000 quasars that sit at the centre of distant galaxies. The data will keep scientists busy for years to come.
SCAN AND DELIVER
Although initially designed as a five-and-a-half-year mission, Gaia has enough fuel to operate for nine years and its instruments are degrading slower than planned, offering the potential to keep operating well beyond its mission parameters. The full Gaia catalogue is scheduled for release in 2022.
MY GOD, IT’S FULL OF STARS…
To marvel at the sight of 1.7 billion stars for yourself, head on over to http://sci.esa.int/gaia/60169-gaia-s-sky-in-colour/or http://sci.esa.int/gaia/60196-gaia-s-sky-in-colour-equirectangular-projection/ and download one of the formats listed on the right-hand side.
The bright horizontal structure in the image is galactic plane, the vast disc of stars and gas viewed side-on. Dark regions are clouds of interstellar gas that obstruct the light of more distant objects. The two larger objects in the lower right are the Large and Small Magellanic clouds, a pair of dwarf galaxies orbiting the Milky Way.