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In early December, an international team of astronomers discovered an incredibly fast rotating star, rotating at a radial velocity of 1.6 million km/h (1 million mph), which is approximately 100 times faster than the sun rotates (roughly four times a day). If the star, dubbed VFTS (short for VLT-FLAMES Tarantula Survey) 102, spun any faster, the centrifugal forces would rip it apart.
Working at the European Southern Observatory’s Very Large Telescope at the Paranel Observatory in Chile, the team located VFTS 102 160,000 light-years away from the Earth in the Tarantula Nebula, which is part of the Large Magellanic Cloud, a satellite galaxy of our Milky Way galaxy. They detected the star because its traveling velocity was 30 km/s (70,000 mph) – much faster than those of other stars in the vicinity.
Philip Dufton, lead author of the paper that presents the team’s findings, stated, “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.” Dufton works at the Department of Physics and Astronomy at Queen’s University Belfast, Northern Ireland. “It was suspicious.”
The centrifugal forces of VFTS 102 (which is a blue giant and has twenty-five times the mass and 100,000 times the luminosity of the sun) are so great that the star has an oblate spheroid shape. Furthermore, they cause VFTS 102 to spin out a disk of plasma at its equator.
The team of astronomers speculate that VFTS 102 had a violent past. It may have been part of a binary star system in which it and its companion star closely rotated around each other. VFTS 102′s fast rotation may have come from the two stars being so close together, which could have caused the companion star to stream gas over to VFTS 102.
Another member of the team, Matteo Cantiello, an astrophysicist at the University of California, Santa Barbara, further explains in the university’s press release, “This gas falls onto the companion star, increasing the mass and spinning it up. Similar to a tennis ball spinning fast after being hit by a glancing blow, a star rotates quickly after being hit off-center by the in-falling gas.”
At some point, the companion star went supernova, expelling much of its gas. The intense explosion ejected VFTS 102, which was sent hurdling through space at the current velocity in which it was discovered. Presently, a supernova remnant and pulsar lie near the blue giant. That these two objects are located nearby VFTS 102 serves as evidence that supports the team’s hypothesis, as the supernova remnant and pulsar may belong to the late companion star, which may have collapsed into a neutron star following its exploding.
“This is a compelling story because it explains each of the unusual features that we’ve seen,” Dufton writes. “This star is certainly showing us unexpected sides of the short, but dramatic lives of the heaviest stars.”