The "river of stars" that paraded through the milky way was hiding in plain sight for a billion years



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The "river of stars" that paraded through the milky way was hiding in plain sight for a billion years

In this stereographic projection, the Milky Way curves around the entire arcuate image, the newly discovered river of stars being displayed in red and covering almost the entire southern hemisphere of the Galactic.

Credit: Astronomy and Astrophysics

A billion years ago, a group of stars formed in our galaxy. Since then, this group has whipped four long circles around the Milky Way. At that time, the gravity of the Milky Way has extended this cluster from a drop to a long stellar stream. At this moment, the stars pass relatively close to the Earth, about 330 light-years away from us. And scientists say this star river could help determine the mass of the entire Milky Way.

Astronomers have already seen these stars, mixed with many stars all around. But until now, they did not realize that the stars were part of a group. The 1,300-light-year-long, 160-light-year-long river winds through the vast and dense starry field of the Milky Way. But the 3D map data of Gaia, a spacecraft of the European Space Agency, showed that the stars of the flow were moving together at about the same speed and in the same direction.

"Identifying nearby disk flows is like looking for the needle in a haystack." Astronomers have long been observing this new flow because it covers most of the night sky, but only now realize that it is there, and it's huge and very close to the sun, "said João Alves, astronomer at the University of Vienna and second author of the newspaper, in a statement. [Large Numbers That Define Our Universe]

Although the space is filled with these stellar flows, they are often difficult to study because they are well camouflaged among the surrounding stars. In general, these stellar flows are also much more distant.

"Finding objects close to home is very useful, it means that they are neither too pale nor too fuzzy to allow further exploration, [an] the dream of the astronomer, "said Alves.

Scientists suspect that star clusters, like the one that eventually became this star flow, can reveal how galaxies get their stars. But in a large and heavy galaxy like the Milky Way, these clusters usually end up being shredded, gravity causing individual stars in different directions. [Amazing Astronomy: Victorian-Era Illustrations of the Heavens]

However, this brook is large enough and heavy enough to remain intact (even if it's stretched) over the billions of years it has encircled the galactic center. And there may be more stars in the stream than those found in the original Gaia data.

Originally published on Science live.

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