A Milky Way Map

The largest all-sky survey of our galaxy is being created

ESA/GAIA/DPAC/AP

This all-sky view of stars in our galaxy—the Milky Way—and neighboring galaxies is based on the first year of observations by the European Space Agency’s Gaia satellite. The observations were made from July 2014 to September 2015.

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.

DANIEL OCHOA DE OLZA—AP

Scientists look under a scaled reproduction of the Gaia surveyor at the European Space Agency center near Madrid, Spain, on September 14.

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.

Do you think the scientists are using what we have learned about maps? If so, what parts of their map would be the same as the ones we drew in class?