Washington, Jan 29 : A new analysis by astronomers has determined that a young star speeding away from the Milky Way had originated from a massive black hole in our neighboring galaxy, the Large Magellanic Cloud (LMC).
It is about nine times the mass of our Sun, about 35 million years old, and it is zooming away from the Milky Way and Large Magellanic Cloud into intergalactic space at 1.6 million miles per hour (2.6 million km/hour).
The conclusion, made by astronomers from the Carnegie Institution and Queen's University Belfast, was based on an analysis of the star's velocity, light intensity and its elemental composition.
The star, dubbed HE 0437-5439, is an early-type star and one of ten so-called hypervelocity stars so far found speeding away from the Milky Way.
According to the results obtained from the analysis, this star was ejected from the galaxy LMC by a yet-to-be-observed massive black hole.
"This star, discovered in 2005, initially appeared to have an elemental makeup like our Sun's, suggesting that it, too, came from the center of our galaxy. But that didn't make sense because it would have taken 100 million years to get to its location, and HE 0437-5439 is only 35 million years old," said Lopez-Morales.
To explain the enigma, the discoverers proposed that HE 0437-5439 was either a so-called blue straggler-a relatively young, massive star resulting from the merger of two low-mass stars from the Milky Way, or it originated from the Large Magellanic Cloud.
"Stars in the LMC are known to have lower elemental abundances than most stars in our galaxy, so we could determine if its chemistry was more like that galaxy's or our own," stated Carnegie astronomer Alceste Bonanos.
The astronomers concluded that the star has originated from the LMC by measuring the relative abundances of certain elements for the first time in any hypervelocity star. The relative abundance of key elements tells them where a star originated.
According to Bonanos, "The concentration of elements in Large Magellanic Cloud stars are about half those in our Sun. Like evidence from a crime scene, the fingerprints point to an origin in the Large Magellanic Cloud."
Based on the speed of the star's rotation measured by the discoverers, and confirmed by this team, the astronomers believe that the star was originally part of a binary system.
The binary could have passed close to a black hole 1,000 the mass of the Sun. As one star was pulled into the black hole, the other was whipped into frenzy and flung out of the galaxy.
"This is the first observational clue that a massive black hole exists somewhere in the LMC. We look forward to finding out where this black hole might be," concluded Bonanos.