A GIANT clump of dark matter may have smashed into a nearby galaxy and punched a hole in its starry disc.
The victim is NGC 247, a small spiral galaxy 11 million light years away, which sports a void that spans a sixth of its diameter. It does harbour some stars, but a new study of Hubble images found they are on average about a billion years older than those surrounding the void.
Stars form when swirling gas coalesces, so the void鈥檚 existence suggests the region was robbed of its gas. 鈥淐learly, something caused this,鈥� says Ata Sarajedini at the University of Florida in Gainesville. 鈥淏ut there鈥檚 no smoking gun.鈥� No visible galaxy lurks nearby that could be the culprit.
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Instead, he and his colleagues invoke an invisible galaxy made of dark matter and a touch of gas (Monthly Notices of the Royal Astronomical Society, ). When this 鈥渄ark subhalo鈥� hit NGC 247, its gas pushed aside the galaxy鈥檚 gas, compressing it into a ring of new stars.
A ring of bright stars surrounding the solar system, called Gould鈥檚 belt, could be evidence that a similar dark subhalo smacked into the Milky Way 30 million years ago.
This article appeared in print under the headline 鈥淒ark matter in hit-and-run smash鈥�
