The fastest-moving stars in the Milky Way, traveling so rapidly that they can escape our cosmic neighborhood, may be runaway stars from a passing galaxy orbiting around our own.
Dubbed hypervelocity stars, they may have been blasted off the front of the so-called Large Magellanic Cloud (LMC), a dwarf galaxy hurtling at a high speed past the Milky Way’s edge, a new study reported.
Where Are These Super-Fast Stars From?
Hypervelocity stars aren’t called as such for nothing: they are large, blue short-lived ones that move up to 1,000 kilometers per second. They maintain up to 10 times the mass of the sun.
At present, there are about 20 hypervelocity stars observed, mostly in the northern hemisphere.
These stars were first speculated to form when a star in a given pair orbiting each other explodes in a supernova, its partner getting shot off at a tremendous speed. They were believed to have been expelled there by a supermassive black hole lying at the center of our galaxy.
"Earlier explanations for the origin of hypervelocity stars did not satisfy me," said Cambridge PhD student and lead author Douglas Boubert in a statement, who cited another mystery: the stars are largely clustered in the Leo as well as Sextans constellations.
His team then proposed that hypervelocity stars may have emerged from the LMC, which journeys past the Milky Way’s outer edge at 400 kilometers per second. The stars are like jumping from an express train, the fastest runaways ejected along the LMC’s orbit toward the two constellations.
The team modeled the scenario on a star coming from the LMC, and the results matched what could be seen in the sky.
More Stars With The Same Velocity And Direction
The stars observed by the researchers were imaged using the Sloan Digital Sky Survey. Another space observatory, the Gaia-ESA satellite from the European Space Agency (ESA), covers a more extensive portion of the vast sky than this survey and is anticipated to provide its first data payload in 2018.
Boubert suggested that the cluster they studied could possibly be part of a huge trail of hypervelocity stars from the LMC.
"I'm thinking they're at the very edge of this trail, the least dense part, so [this] implies that there are thousands more in the southern sky," he said in an ABC report.
The findings were detailed in the journal Monthly Notices of the Royal Astronomical Society.
Another recent study suggested that all stars, including the solar system’s sun, are likely born with a twin.
Many stars are known to have companions, such as Alpha Centauri, the closest star system to the solar system, consisting of three stars. Astronomers wonder if binary and triple star systems are born that way or if they just fall in together after they have formed.
