spaceSpace and Physics

Most Detailed Map Of Milky Way Yet Reveals Precise Positions Of Over 1.8 Billion Stars


Dr. Alfredo Carpineti

Senior Staff Writer & Space Correspondent

clockDec 3 2020, 15:06 UTC

This is not a picture of the Milky Way. This is a map created with the data from the Gaia spacecraft. ESA/Gaia/DPAC; CC BY-SA 3.0 IGO. Acknowledgment: A. Moitinho.

The most detailed and accurate map of the Milky Way yet has been unveiled. The European Space Agency’s Gaia observatory has published the first part of its third data release improving upon the incredible map of our galaxy produced in previous publications. Gaia has now measured the position of almost 1.812 billion stars with unparalleled precision.

This is not only more accurate than any map produced before Gaia, but astronomers have also improved on the incredible precision reached in the second Gaia data release (DR2) in 2018. The uncertainty on distances is now 0.71 times smaller compared to DR2. Gaia also measured the 3D velocity of almost 1.5 billion stars as well and the new catalog has 0.44 smaller uncertainty on the proper motions of these objects.


“Gaia EDR3 is the result of a huge effort from everyone involved in the Gaia mission. It’s an extraordinarily rich data set, and I look forward to the many discoveries that astronomers from around the world will make with this resource,” Timo Prusti, ESA’s Gaia Project Scientist, said in a statement. “And we’re not done yet; more great data will follow as Gaia continues to make measurements from orbit.”

The incredible map is a great step forward for astronomy and cutting-edge science is already being carried out thanks to this new data. The Gaia data has been used to precisely measure the acceleration of the Solar System towards the center of the Milky Way. This tiny and gentle pull is about 7 millimeters per second with an uncertainty of about half a millimeter. This means that every second the trajectory of the Solar System is deflected by the diameter of an atom, amounting to about 115 kilometers (71 miles) in a year.

The most precise 3D map of the Milky Way yet.

The data was also used to study the edge of the Milky Way's disk, the so-called anticenter. It shows populations of stars moving in a very strange manner. A slow-moving population is moving downwards towards the plane of the Milky Way, while a fast-moving population is moving upwards. This peculiar effect might be the consequence of galactic cannibalism.


Yes, our own Milky Way is in the process of absorbing one of its companion galaxies, the Sagittarius Dwarf. A close flyby of this small galaxy sometime between 300 and 900 million years ago, created ripples in the stellar disk.

Gaia was also used to look at two other companions of the Milky Way, the Large and Small Magellanic Clouds. The Gaia data allowed for accurate maps of the two galaxies as well as the faint bridge of gas and stars that connects them.  

Data from Gaia’s Early Data Release 3 shows how stars are being pulled from the Small Magellanic Cloud, and heading towards the adjacent Large Magellanic Cloud, forming a stellar bridge through space. ESA/Gaia/DPAC; CC BY-SA 3.0 IGO. Acknowledgments: S. Jordan, T. Sagristà, X. Luri et al (2020).

The EDR3 has also allowed for the most comprehensive survey of the solar neighborhood. Within 336 light-years (100 parsecs), there are 331,312 stellar objects. This is estimated to be 92 percent of the true population. What’s missing from the catalog is some of the faintest, coolest dwarfs although the team believes they have observed many of them. They have also tracked how these will move over the next 1.6 million years and how the night sky will change. 

Simulations of the future motion and position of stars were also conducted for 75,000 local stars. The scientists tracked where they will eventually be over the next 500 million years. 


Orbits of the nearby stars around the galaxy

The catalog and multiple scientific papers on its discoveries are published in Astronomy & Astrophysics. The full data release will be published in 2022, the year the mission nominally ends, although the team has put forward a proposal for an extended mission into 2025.

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