ESA’s Gaia spots stars flying between galaxies

ESA’s Gaia spots stars flying between galaxies

Based on these data, they constructed the distribution of speeds and distances for 7 million stars in the milky Way.

"Rather than flying away from the Galactic center, most of the high-velocity stars we spotted seem to be racing towards it", says Tommaso Marchetti who used an artificial neural network, which is software created to mimic how our brain works to helps Gaia catch speeding stars. Or they might have originated in a galaxy even farther away.

In December of 2013, the European Space Agency (ESA) launched the Gaia mission.

Milky Way galaxy contains about a hundred billion stars. The study was led by Tommaso Marchetti, a PhD candidate from the Leiden Observatory, and included Elena Rossi (an associate professor at Leiden) and Anthony Brown - the chair of the Gaia Data Processing and Analysis Consortium (DPAC) Executive.

The Milky Way is apparently a hotspot for stars immigrating from other galaxies.

"Of the seven million Gaia stars with full 3D velocity measurements, we found twenty that could be travelling fast enough to eventually escape from the Milky Way". They move around at a variety of velocities depending on their location in a galaxy and their motion could provide key information about the history of a particular galaxy. If this hypothesis is correct, studying them, researchers will be able to describe the mechanisms of star formation in other galaxies, and to determine whether supermassive black holes, as they tend to give luminaries such high speed. If true, then these stars will carry the imprint of their site of origin. Unusually, 13 of the stars appeared to be extragalactic.

Study co-author Dr Elena Maria Rossi, also from Leiden University, said: 'Stars can be accelerated to high velocities when they interact with a supermassive black hole. "So the presence of these stars might be a sign of such black holes in nearby galaxies". How could we? The data for so many stars would be (are) massive; collecting the data, storing them and analyzing them requires today's spacecraft and computer technologies.

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The research team acknowledges that there is another possibility. Therefore, it's possible that ancient interactions between the Milky Way and one of its dwarf galaxies shoved some halo stars inward, though the study points out this scenario would imply the Milky Way is more massive than is now believed. However, if they turn out to be chock-full of heavy elements, then numerous hypervelocity stars may have extragalactic origins. Interaction distant part of the milky way with flying by the galaxy caused the collision because of the strong attraction.

ESA's Gaia mission is proving to be a great provider of fascinating data.

For 7 million of the brightest stars in the set, Gaia managed to obtain 3D motions by also measuring how quickly the stars were moving toward or away from the Earth. Most are located in the galactic disc with a dense bulge at its center, while the remaining stars are distributed in a wider spherical halo.

Only a small number of hypervelocity stars have ever been discovered, and Gaia's second data release provides a unique opportunity to look for more of them.

These latest results once again demonstrate just how effective the Gaia observatory has been in its mission.

Fortunately, Gaia is expected to release at least two more datasets in the 2020s.

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