Fastest rotating star found in neighboring galaxy

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Astronomers think the sun may have had a violent past and has been ejected from a double star system by its exploding companion.
By STScl, Baltimore, Maryland — Published: December 6, 2011
Star VFTS 102

Astronomers have found the fastest spinning star ever discovered. The hot blue giant rotates at a dizzying 1 million mph (1.6 million km/h), or 100 times faster than our Sun. The star is close to the point that it would be torn apart due to centrifugal forces if it spun any faster.

Two researchers at the Space Telescope Science Institute in Baltimore, Maryland, Selma de Mink and Daniel Lennon, are part of an international team of astronomers who used the European Southern Observatory’s Very Large Telescope at the Paranal Observatory in Chile to find the massive, bright young star, called VFTS 102. It lies in a neighboring dwarf galaxy, the Large Magellanic Cloud, about 160,000 light-years from Earth. Astronomers think that it may have had a violent past and has been ejected from a double star system by its exploding companion.

The astronomers also found that the star, which is around 25 times the mass of the Sun and about 100,000 times brighter, was moving through space at a significantly different speed than its neighbors.

“The remarkable rotation speed and the unusual motion compared to the surrounding stars led us to wonder if this star had an unusual early life,” said Philip Dufton from Queen’s University Belfast, Northern Ireland. “It was suspicious.”

This difference in speed could imply that VFTS 102 is a runaway star — a star that has been ejected from a double star system after its companion exploded as a supernova.

The team suggests that the star could have started life as one component of a binary star system. If the two stars were close, gas from the companion could have streamed over, and, in the process, the star would have spun faster and faster. This would explain one unusual fact — why it is rotating so fast. After a short life of about 10 million years, the massive companion would have exploded as a supernova. The explosion would have led to the ejection of the star and could explain the second anomaly — the difference between its speed and that of other stars in the region. As it collapsed, the massive companion would then have turned into a pulsar. It is intriguing that there is a nearby supernova remnant and a pulsar. What is not yet clear is whether or not they are related to VFTS 102.

Yet the astronomers cannot be sure that this is exactly what happened. “This is a compelling story because it explains each of the unusual features that we’ve seen,” said Dufton. “This star is certainly showing us unexpected sides of the short but dramatic lives of the heaviest stars.”

To test this theory, Lennon and de Mink will use NASA’s Hubble Space Telescope to make precise measurements of the star’s proper motion across space.


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