Milky Way is due to collide with its largest neighbor

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Milky Way is due to collide with its largest neighbor

Andromeda, which is currently 2.5 million light-years away, is hurtling toward the Milky Way at nearly 250,000 miles an hour

Monday February 11, 2019 7:16 PM, ummid.com News Network

Milky Way Andromeda

Milky Way, our galaxy, is due to collide with its largest neighbor - a sparkling collection of stars called the Andromeda galaxy. This cataclysm has been foretold by well-known physics, and astronomers know that when the space dust clears, neither galaxy will look the same: Within a billion years or so of first contact, the two will merge and form a much larger, elliptical galaxy.

But new measurements of stars within Andromeda, made by the European Space Agency’s Gaia space telescope, are changing predictions for when, and exactly how, that collision will go down, according to a report by National Geographic.

As astronomers report in the Astrophysical Journal, the originally predicted crash date of 3.9 billion years from now has been pushed back by about 600 million years. And instead of a head-on collision, astronomers are predicting more of an initial glancing blow—kind of like knocking into a neighbor’s rear-view mirror.

“The overall picture is not too different. But the exact orbital pathways are different", says study author Roeland van der Marel of the Space Telescope Science Institute.

Andromeda, which is currently 2.5 million light-years away, is hurtling toward the Milky Way at nearly 250,000 miles an hour.

Astronomers have known this since Vesto Slipher first aimed a telescope at Andromeda and measured the galaxy’s motion in 1912. (He didn’t know it was a galaxy at the time, when conventional wisdom suggested it was a nebulous cloud inside the Milky Way. Needless to say, Slipher’s calculations suggested that idea needed revising).

Later, astronomers using the Hubble Space Telescope were able to measure the sideways motion of Andromeda, which determines whether the galaxies are destined for a direct hit or a cosmic brush-pass. Using those observations, in 2012 van der Marel and his team forecast a head-on collision in roughly 3.9 billion years—a prediction they’ve just revised.

“It is interesting, even though it is in some ways a fairly minor modification of what was known previously,” says Brant Robertson of the University of California, Santa Cruz.

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