Google Maps Eat Your Heart Out
The goal of mapping the heavens has existed for as long as the science of astronomy. The first known comprehensive star catalogue was drawn up by Greek astronomer Hipparchus 2,000 years ago, and in 1989 the European Space Agency continued his legacy and launched the High Precision Parallax Collecting Satellite (Hipparcos for short), which mapped 120,000 stars over three and a half years.
Now, ESA’s next sky cartographer is Gaia (Global Astrometric Interfermeter for Astrophysics).
Gaia was launched on December 19 and is now speeding to the second Lagrange point 1.5 million kilometres from Earth, where—free of the bother of the atmosphere—it will carry out 40 million measurements per day and produce a 3D atlas of the cosmos. Over five years it will chart 1 billion stars (1% of the Milky way’s inventory) with forty times the accuracy of Hipparcos. ESA describes: “If Hipparcos could measure the angle that corresponds to the height of an astronaut on the Moon, Gaia will be able to measure his thumbnail.”
The mission is expected to yield some incredible discoveries—it will shed light on the distribution of dark matter, track half a million asteroids, find new supernovae and novae, observe millions of galaxies and quasars, and discover over 30,000 exoplanets.
Gaia will repeat its measurements 70 times to ensure accuracy, and by combining all of these, astronomers can construct a final, incredibly precise map. This information will give us clues about the stars’ history, so Gaia will help us build a family tree of our home galaxy.