Extragalactic stars found zipping through the Milky Way

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In a new study published in Monthly Notices of the Royal Astronomical Society, a trio of astronomers set out to find hypervelocity stars fleeing our galaxy, but surprisingly discovered most of the rapidly moving stars are actually barreling into the Milky Way from galaxies beyond.

"Rather than flying away from the [Milky Way's] Galactic Center, most of the high velocity stars we spotted seem to be racing toward it," said lead author Tommaso Marchetti, a PhD candidate at Leiden Observatory, in a press release. "These could be stars from another galaxy, zooming right through the Milky Way."

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Out of the 20 excessively speeding stars they found, the researchers pinpointed seven so-called "hyper-runaway star candidates," which are escaping stars that seem to originate from the Milky Way's galactic disk. Meanwhile, none of stars appear to come from the Milky Way's core, and the remaining 13 unbound stars (including the two fastest, which zip through our galaxy at about 1.5 million miles per hour) cannot be traced back to the Milky Way at all.



Gaia

Gaia is a space observatory of the European Space Agency (ESA) designed for astrometry: measuring the positions and distances of stars with unprecedented precision.[7][8] The mission aims to construct the largest and most precise 3D space catalog ever made, totalling approximately 1 billion astronomical objects, mainly stars, but also planets, comets, asteroids and quasars among others.[9]