FOR something so enormous, astronomers know remarkably little about the Milky Way, Earth’s home galaxy. They know its rough dimensions—somewhere between 100,000 and 180,000 light-years across. And they know that it contains 100bn stars—or perhaps 200bn, or maybe even twice that again.
For part of the galaxy, though, things are about to become much clearer. On April 25th the European Space Agency’s Gaia satellite released one of the biggest chunks of data in the history of astronomy. Around 1.3bn stars, perhaps about 1% of the Milky Way’s total, have had their position, brightness and motion measured accurately for the first time.
The result is a stellar atlas of unprecedented size and accuracy—as well as great beauty. Gerry Gilmore, an astronomer at the University of Cambridge and one of Gaia’s scientists, showed an audience in London a slice of space so thick with stars that...Continue reading
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