The ESA’s Gaia spacecraft has already been studying the Milky Way galaxy for several years, and the first release of data included the precise location of more than 2 million stars. Now, the second major dataset from Gaia has pinpointed the position and brightness of 1.7 billion stars in our galaxy. The ESA has used this data to produce the most detailed map of the Milky Way yet.
Gaia contains three instruments for observing stars, allowing it to determine the location, color, and movement of stars over time. Gaia calculates the distance to stars, which astronomers consider the most critical data point, using parallax measurements. Gaia does that by checking a star’s apparent motion at two different points in its orbit and separating that from its true motion in the galaxy. The spacecraft will monitor each target star about 70 times over the course of five years, which is the planned mission duration. We’re getting toward the end of the mission, so Gaia has sent back a huge volume of data.
There are around 100 billion stars in the Milky Way, so knowing about a billion of them is still just a drop in the bucket. However, previous measurement could only nail down about 100,000 stars. With Gaia’s data, scientists have determined the location and apparent brightness of 1.7 billion stars, but that’s not all. The ESA has more detail on an impressively large subset of those celestial bodies. We also know the color of 1.4 billion stars, the distance, and motion of 1.3 billion. For a smaller number of stars, we have even more detail. The ESA says 161 million stars now have accurate surface temperature measurements in the database, 77 million have known radii, and we know the radial velocity of 7 million.
In the image above, the ESA has generated a map of the Milky Way from Gaia’s perspective using location, color, and brightness data. Using the Gaia data from 22 months of observations, scientists are closer than ever to mapping the galaxy. Gaia’s original mission mandate will expire at the end of this year, but it’s likely the ESA will grant an extension. Gaia has enough fuel to continue operating for about four more years, assuming there are no mechanical failures.
The Gaia mission itself is not intended to make the big discoveries. It’s just creating a catalog of stars in the sky. Scientists in the community will use that data to study the galaxy and learn more about its past, present, and future.
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