Astronomers have discovered a star from another galaxy

ESA Marchetti NASA Hubble

Using the latest data from ESA's Gaia mission, researchers searched for these high-velocity stars in the Milky Way galaxy.

The reconstructed positions and orbits of 20 high-velocity stars, represented atop an artistic view of the Milky Way. If this is the case, they carry the footprint of their original site and study them at much closer distances than their parent galaxy could provide unprecedented information on the nature of stars in another galaxy – similar to a study Martian material brought to our planet by meteorites. Surprisingly, the study also revealed thirteen stars, indicated in orange, that are running towards the Milky Way: it could act as stars from another galaxy, zooming in on the our. Image via ESA / Marchetti et al. Most are located in a dense, domed center disk; the rest is distributed in a much larger spherical halo.

Stars, including the sun, spin around the center of the galaxy hundreds of kilometers per second. The consensus is that these fast-moving stars begin life in the middle of the Milky Way, before being thrown further and further away.

In a research published in the Monthly Notices of the Royal Astronomical Society, astronomers from the Leiden Observatory in the Netherlands discovered 20 hyper-velocity stars of this type, but only seven of them seemed to be Away from the Milky Way.

Contrary to what they expected, the team found that most of the HVS they had noticed were running towards the center of the Milky Way and not away from it.

Astronomers believe that stars can come from the great megellanic cloud, a small galaxy orbiting the Milky Way. They move at different speeds depending on their location in a galaxy and their movement could provide essential information about the history of a particular galaxy.

But even without a supermassive black hole, it's still possible for another galaxy to eject some of its stars. "The presence of these stars could therefore be the sign of such black holes in neighboring galaxies".

On the other hand, scientists do not rule out that these stars could already be part of a binary system and be eliminated after a supernova explosion. "Anyway, studying them could tell us more about this type of process in nearby galaxies". Essentially, these newly identified HVS can come from the halo of our galaxy, but were then accelerated and repelled when the Milky Way began to come into contact with one of the many dwarf galaxies with which it fused during its history. However, if they turn out to be filled with heavy elements, many hypervelocity stars may have extragalactic origins.

According to the study, some of these flaming beasts seem almost indistinguishable from the Milky Way's halo stars, who are the oldest stellar residents of our galaxy and encapsulate the galaxy in a giant diffuse sphere.

"Watching the colors of the stars tells us more about what they are made of".

Fortunately, Gaia is expected to release at least two more datasets in the 2020s. "CA will help [researchers] find hundreds or thousands of hypervelocity stars, understand their origin in more detail and use them to study the Galactic Center environment, as well as the history of our galaxy ", did he declares.