A Rare Type Of Runaway Star Has Been Seen Speeding Through Another Galaxy

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Scientists have spotted an unusual “runaway” star in a nearby galaxy, the first yellow supergiant star of this kind ever seen.

Led by Kathryn Neugent from Lowell Observatory in Arizona, researchers studied the star called J01020100-7122208 in the Small Magellanic Cloud (SMC). This galaxy is located about 200,000 light-years from us, one of our closest neighbors.

“The star is the first runaway yellow supergiant star ever discovered, and only the second evolved runaway star to be found in another galaxy,” a statement from Lowell Observatory noted.

The discovery was made using the Magellan telescope at Las Campanas Observatory in Chile. A pre-print of the findings, which will be published in The Astronomical Journal, is available on arXiv.

The star was found to be traveling at about 480,000 kilometers (300,000 miles) per hour, having traveled through space for 10 million years. It’s currently located towards the outer part of the SMC, and is likely far from where it was formed.

The truly unusual thing about this star, though, is its size. It is a yellow supergiant, which is an extremely short-lived phase of a star’s life, lasting just 10,000 to 100,000 years. So it’s pretty lucky we got to see it in this stage.

The star is 10 million years old and nine times the mass of our Sun. It probably began in a binary system before being flung out into space when its companion star went supernova.

This is not the first nor the fastest runaway star we’ve seen. About two dozen have been discovered in our galaxy so far, some of which have speeds of up to 3.5 million kilometers (2.2 million miles) per hour, known as hypervelocity stars.

Finding a yellow supergiant runaway star is pretty neat, though. It will eventually explode as a supernova, probably in about 3 million years or so, far from where it was created. This will be after it has expanded to a red supergiant, with a size equivalent to the orbit of Mars or Jupiter around the Sun.

The resulting supernova remnant from that explosion could form new stars or even new planets at the edge of the SMC. And the authors note this may be a mechanism in the universe for spreading elements throughout a galaxy.

“Such stars may provide an important mechanism for the dispersal of heavier elements in galaxies given the large percentage of massive stars that are runaways,” they wrote.

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