The largest all-sky survey of our galaxy is being created
Nearly a million miles from Earth is the greatest little mapmaker that ever existed. It is located at a gravitationally stable point in space on the opposite side of our planet from the sun. It had better be great because it has a huge job: To paint a three-dimensional picture of the entire galaxy. Our galaxy is a structure measuring 100,000 light years across. A light-year is a unit of distance equal to the distance that light travels in one year—5.88 trillion miles. This is an awful lot of territory to keep your eye on.
The mapmaker is the Gaia satellite. It is a 4,500-pound craft launched by the European Space Agency in 2013. Gaia’s mission managers don’t pretend they can spot every object in the galaxy. It includes an estimated 300 billion stars, planets, moons, asteroids and more. But a good 1 billion stars ought to help the managers measure the Milky Way overall. The objects should reveal new clues about the galaxy’s structure, formation, and history.
This image, released on September 14, provides a first rough glimpse at the map to come. So far, Gaia has exceeded its original goal. It has gotten a reasonably good handle on 1.142 billion stars. Much more precise positional measurements, along with the stars’ apparent motion relative to Earth, are still to come.
Space is a very big place. It will be a long, long time before we map it all. But Gaia offers a good start.
SEP 21, 2016 | By Jeffrey Kluger; adapted by TFK editors