Artist impression of the Gaia spacecraft.
Illustration: ESA

Astronomers from the European Space Agency’s Gaia mission will release the biggest map of our galaxy ever tomorrow, using data collected by the Gaia space telescope. That includes 1.7 billion stars, as well as new information that could potentially solve some cosmic mysteries.

The ESA’s Gaia telescope launched in 2013 and soon after began its galaxy-mapping mission. Back in 2016, it released position and brightness data for 1.1 billion stars, and tomorrow’s release, called DR2, will bump the catalog up to almost 1.7 billion stars. It’s a big deal.

“It will be the most precise and complete stellar catalog ever produced,” Gaia Science Operations Manager Uwe Lammers told Gizmodo.

Gaia stats
Graphic: ESA

The second data release covers much more space than the first release did, expanding the map’s reach from 500 to 8,000 light-years out, Lammers explained. It’ll also add further data on stellar temperatures, velocities, and parallaxes (aka, how the stars have moved compared to even farther objects, such as bright quasars in other galaxies).

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There are all sorts of questions such data could help answer. Scientists can’t agree on how quickly the universe is expanding, and we don’t know how many spiral arms the Milky Way galaxy has, for example.

Emily Rice, astronomer from CUNY College of Staten Island and the American Museum of Natural History, summed things up with a meme:

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“Gaia is an unprecedented map of the Milky Way galaxy, fundamental astrophysics at its finest, laying the groundwork for decades of research on everything from the Solar System to the origin and evolution of the Universe,” Rice told Gizmodo. “It is at once foundational and transformative, which is rare in modern astronomy.”

But even DR2 isn’t the whole story. A third data release will hopefully come in late 2020, said Lammers. That release will add spectral data, or the specific wavelengths of light that a star releases. That could help further determine what they’re made of. After all, the Milky Way seems to have about a hundred billion stars—Gaia’s map will depict a few billion.

Even then, Gaia has some innate drawbacks. It can’t peer through dust, so there will be black spots in tomorrow’s map, astrophysicist Iain McDonald from the University of Manchester told Gizmodo. An infrared-detecting telescope would be needed to overcome such a limitations.

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But there’s sure to be some cool images in tomorrow’s release. I asked Lammers whether we might be able to see the galactic spiral arm that contains Earth—he said we’d need to wait and see.

“It will be spectacular. I can promise you that,” he said. “We’re all very excited about it.”

We’re excited, too. Look for our coverage of the data release tomorrow morning.

Update 4/25/2018: It’s here!

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