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Fastest rotating star
lives next door

DR EMILY BALDWIN
ASTRONOMY NOW
Posted: 06 December 2011


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Using the European Southern Observatory's Very Large Telescope, astronomers have found the fastest rotating star known, residing in our neighbouring galaxy the Large Magellanic Cloud, and which likely suffered a violent past.

The star in question, VFTS 102, rotates more than three hundred times faster than our own Sun, a dizzying two million kilometres per hour. It is 25 times the mass of the Sun and one hundred thousand times brighter.


Artist's impression of the fastest rotating star, which spins so fast it has flattened and spun out a disc of hot plasma. Image: NASA/ESA and G. Bacon (STScI).

The plot thickened with the observation that VFTS 102 was found to be moving through space at a racier pace than its neighbours.

One explanation is that it began life in a binary system, but was booted out when its companion exploded as a supernova. A pulsar and a nearby supernova remnant bolsters this idea.

Starting as a binary star, gas from the companion spilled over onto the star, causing it to spin faster and faster. As the companion exploded, the star was propelled out of the system by the shock waves emanating from the dying star, explaining its high speed getaway. Left at the scene, the massive companion collapsed into a pulsar, completing the puzzle.

“This is a compelling story because it explains each of the unusual features that we’ve seen,” says Philip Dufton of Queen’s University Belfast, and lead author of the paper presenting the results in the Astrophysical Journal Letters. “This star is certainly showing us unexpected sides of the short, but dramatic lives of the heaviest stars.”


In this view of the Large Magellanic Cloud lies the fast-rotating star VFTS 102 (arrowed), 160,000 light years from Earth. The image includes both visible-light and infrared images from the Wide Field Imager at the MPG/ESO 2.2-metre telescope at La Silla and the 4.1-metre infrared VISTA telescope at Paranal. Image: ESO/M.-R. Cioni/VISTA Magellanic Cloud survey. Acknowledgment: Cambridge Astronomical Survey Unit.

Dufton adds that it will also be interesting to consider the star's fate. "Assuming a space velocity of 40 kilometres per second for VFTS102 our evolutionary models imply that VFTS102 will travel 300-400 parsecs before ending its life. This is consistent with [previous] findings that the locations of three nearby gamma-ray bursts were found several hundred parsecs away from their most likely progenitor birth locations."

Astronomers will now use the Hubble Space Telescope to make precise measurements of the motion of both the star and pulsar to try and decipher its curious past.

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