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Posted on 3 Oct. 2018
"Rather than fleeing the galactic center, most of the high-speed stars we've seen seem to be heading towards him," says Tommaso Marchetti, who used a network of artificial neurons, software designed to mimic how our brain works. in order to help Gaia catch the fast stars. "These could be stars from another galaxy, zooming through the Milky Way."
A team of astronomers using the latest data from ESA's Gaia mission to search for high velocity stars chased from the Milky Way was surprised to find them instead, but perhaps in another galaxy. The study is published in the journal Avis of the Royal Astronomical Society.
Stars revolve around our galaxy at hundreds of kilometers per second and their movements contain a wealth of information about the past history of the galaxy. The fastest class of these stars is called hypervelocity stars. It is thought that they begin their lives near the galactic center, before jumping on the edge of the Milky Way via interactions with the black hole at its center.
Only a small number of hypervelocity stars have ever been discovered, and Gaia's second publication of recently published data offers a unique opportunity to research others.
"Of the seven million Gaia stars with full 3D speed measurements, we found twenty people who could travel fast enough to eventually escape the Milky Way," says Elena Maria Rossi, one of the authors of the new study based at the University of Leiden. in the Nederlands.
It is possible that these intergalactic intruders come from the Large Magellanic Cloud, a relatively small galaxy orbiting the Milky Way, or that they come from a galaxy even further away. 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.
"Stars can be accelerated at high speeds when they interact with a supermassive black hole," explains Elena. "The presence of these stars could therefore be the sign of such black holes in neighboring galaxies. But the stars may have also been part of a binary system, projected toward the Milky Way when their companion star exploded as a supernova. Anyway, studying them could tell us more about this type of process in neighboring galaxies. "
Another explanation is that the recently identified sprint stars could be native to the halo of our galaxy, accelerated and pushed inward through interactions with one of the dwarf galaxies that have fallen to the Milky Way during its history. Additional information on the age and composition of stars could help astronomers clarify their origin.
New data will help clarify the nature and origin of these stars with greater certainty, and the team will use ground-based telescopes to learn more about them. At least two other Gaia data releases are planned in the 2020s, and each will provide more accurate and news information on a larger number of stars.
"We are ultimately predicting complete 3D velocity measurements for up to 150 million stars," says Anthony Brown, co-author, chairman of the board of Gaia Data Processing and Analysis. Consortium. "This will help us find hundreds, if not thousands, of hypervelocity stars, to understand their origin in more detail and to use them to study the galactic center environment as well as to find them. history of our galaxy, "he adds.
"This exciting result shows that Gaia is a true discovery machine, paving the way for totally unexpected discoveries on our Galaxy," concludes Timo Prusti, Gaia project scientist at ESA.
The Daily Galaxy via the Royal Astronomical Society
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