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Weird Structures Found to Be Ancient Leftovers of Violent Milky Way Collision
EVAN GOUGH, UNIVERSE TODAY26 OCTOBER 2020
In 2005 astronomers found a dense grouping of stars in the Virgo constellation. It looked like a star cluster, except further surveys showed that some of the stars are moving towards us, and some are moving away. That finding was unexpected and suggested the stream was no simple star cluster.
A 2019 study showed that the grouping of stars is no star cluster at all; instead, it's the hollowed-out shell of a dwarf spheroidal galaxy that merged with the Milky Way. It's called the Virgo Overdensity (VOD) or the Virgo Stellar Stream.
A new study involving some of the same researchers shows how and when the merger occurred and identifies other shells from the same merger.
The new paper's title is 'The Milky Way's Shell Structure Reveals the Time of a Radial Collision'. The first author is Thomas Donlon II, a Rensselaer grad student, who was also the first author of the 2019 study. The paper is published in The Astrophysical Journal.
More:
https://www.sciencealert.com/astronomers-find-the-hollowed-out-shell-of-a-dwarf-galaxy-that-collided-with-the-milky-way
