Milky Way has 1.7 billion stars!

Paris: Europe’s Gaia satellite has produced a 3-D map of more than a billion stars in the Milky Way galaxy — complete with their distance from Earth, colour, and motion through space.

The eagerly-anticipated catalogue, published on Wednesday, was compiled from data Gaia gathered on some 1.7 billion stars from its unique vantage point in space, about 1.5 million kilometres from the earth.

Rich dataset

“The dataset is very rich and we believe it will revolutionise astronomy and our understanding of the Milky Way,” said Gaia’s scientific operations manager Uwe Lammers.
“This catalogue is the most precise, most complete catalogue that has ever been produced. It allows studies which have not been possible before.”

Launched in 2013, Gaia started operating the following year, gathering data on 1,00,000 stars per minute — some 500 million measurements per day. Its first map was published in September 2016, based on a year’s worth of observations of about 1.15 billion stars.

An update, launched at the ILA international air and space show in Berlin, adds stars and provides more data on each one, from measurements taken over 22 months in 2014-2016.

Precision priority 

“For some of the brightest stars in the survey, the level of precision equates to Earth-bound observers being able to spot a €1 coin lying on the surface of the moon,” said an ESA statement.

The new, improved map depicts 1.7 billion stars “for which we can tell where they are in the sky with very high accuracy, and how bright they are,” said Anthony Brown of the Gaia Data Processing and Analysis Consortium.For 1.3 billion of those, “we know their distance and we know how they move through space.”

There is, furthermore, information on the radial velocities of some seven million stars — indicating the rate at which they are moving towards, or away from, the earth.

With all this data, “we can make a map of the whole night sky,” said Mr. Brown, who described the end result as “stunning”. “You see the whole Milky Way in motion around its axis,” he said.

Web of space rocks

Gaia also revealed the orbits of some 14,000 “solar system objects” — mapped as an intricate web of space rocks shooting around the sun. “It represents the most accurate survey ever of asteroids in the solar system,” said Mr. Brown. More will be added in future updates.

Information sent to the earth by Gaia is collated by 450 scientists from 20 countries. Antonella Vallenari, one of the scientists, likened the data release to “opening a chocolate box”.

“It’s very, very exciting,” she said at the launch event in Germany, webcast live.The full data will be published in a series of scientific papers in a special issue of the journal Astronomy & Astrophysics, laying the foundation for decades of further study.

 “We are really getting today the catalogue of a billion stars zipping through the Milky Way in various directions,” said Guenther Hasinger, ESA’s director of science. “With Gaia, we can actually deconstruct the whole history of the Milky Way. It’s like archaeo-astronomy... to really build up the history of our universe.”