Astronomers have spotted a giant 'runaway star' speeding through the Andromeda galaxy; the first of its kind seen outside the Milky Way.
Whereas most stars flow together around the centre of their galaxy, some, known as runaways, travel at different directions and speeds to their peers, and may even escape their galaxy entirely. Spotting red-supergiant runaways is rare — stars in this late stage of life left their birthplace long ago, making their unusual speeds harder to spot than for younger runaways.
Kate Evans and Philip Massey at the Lowell Observatory in Flagstaff, Arizona, studied a red supergiant in the Andromeda galaxy known as J004330.06+405258.4 and calculated that it is travelling 400–450 kilometres per second faster than its neighbours. The star is the first massive runaway to be spotted outside our own galaxy and the fastest anywhere for its size, say the authors.
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Red-giant rogue in Andromeda. Nature 526, 612 (2015). https://doi.org/10.1038/526612c
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DOI: https://doi.org/10.1038/526612c
