The European Space Agency Just Launched a Spacecraft To 3D Map the Galaxy

Last Thursday, the European Space Agency launched the coolest mission you’ve probably never heard of: Gaia. Gaia is a spacecraft designed to create a three-dimensional map of the Milky Way by charting a billion stars over time, revealing our galaxy’s composition, formation, and evolution in the process.

The core piece of the Gaia spacecraft are two distinct modules, a payload module and a service module. The payload module is built around a central torus (or doughnut-shaped) optical bench a little less than 10 feet in diameter. This torus provides the structural support for the instrument that gathers astrometry data (the positions, motions, and magnitudes of stars), photometry data (the intensity of light), and spectrometry data (light spectral analysis for information on star composition. The service module contains all the mechanical, structural, and thermal elements that support the spacecraft’s instruments and electronics, and also houses the micro-propulsion system, the deployable sunshield, the thermal tent, and the solar arrays. It’s also the module that supports the payload module’s instruments, allowing them to gather detailed stellar information.

Using it’s instruments, Gaia will measure the motions of one billion stars as they orbit the black hole at the center of our galaxy. But it won’t just look at each star once; Gaia will take measurements of its one billion target stars 70 times each. This is going to create a record of each star’s brightness and position over time.

And Gaia will do this incredible survey from the Lagrange point L2, a gravitationally stable point a little more than 932,056 miles from the Earth away from the Sun. The spacecraft will have to make a few adjustments from time to time to stay solidly at L2, but the tradeoff is the unique vantage point that will give Gaia an uninterrupted, eclipse-free view of the entire celestial sphere over the course of a year. With a five-year primary mission, Gaia will have ample opportunity to gather the data scientists are after.

This is the second celestial mapping mission the European Space Agency has launched. In 1989, it launched Hipparcos, history’s first satellite designed to chart the positions of stars. Hipparcos created two stellar catalogues, the first of about 118,000 stars and the second of over 2 million, both of which have been widely used by professional astronomers. These catalogues helped astronomers predict that comet Shoemaker-Levy would impact Jupiter and helped astronomers refine the age of the universe.

Gaia is set to upstage Hipparcos. Not only can this new spacecraft collect more than 30 times as much light as its predecessor, it can measure a star’s position 200 times more accurately. Gaia will also use modern CCDs to take wide-angle images, meaning it can observe more points of light in a single frame.

So how will a map of a billion stars tell scientists about our galaxy’s formation and composition? A lot of information will come from tracking stellar movement. Because stars typically gain some motion not long after their birth, looking deep into the middle of our galaxy (which is the same as looking back in time) will tell astronomers how they moved early in their lives and shed light on how the Milky Way was formed.

Scientists expect to make some unexpected discoveries thanks to Gaia’s mapping, too. Combining the spacecraft’s detailed measurements of one billion stars with highly accurate astrometric data, Gaia’s catalogue will doubtless help astronomers find other objects in our cosmic neighborhood—exoplanets, comets, icy bodies, and possibly even distant supernovae. And who knows what astronomers might find decades from now, looking back through Gaia’s massive database armed with another decade or generation’s worth of experience and knowledge about our galaxy.

To keep tabs on the mission, check out ESA’s Gaia blog.

@astVintageSpace