Lonely young star caught in a growth spurt
Is this object an anomaly or do all stars go through this dramatic stage in their youth?
All alone, a solitary star has been spotted gorging on surrounding dust and gas. Chris Britt from Texas Tech University and an international squad of colleagues describe the lonely object called CX330, one of only 10 of its kind discovered so far, in the Monthly Notices of the Royal Astronomical Society.
Flashes of X-ray light from CX330 was first detected in 2009 by NASA's Chandra X-Ray Observatory, and further observations showed it was object in our galaxy emitting optical light as well. With only these clues, though, scientists had no idea what it was.
So when Britt and colleagues examined infrared images of the same area taken with NASA's Wide-field Infrared Survey Explorer (WISE) in 2010, they realised this object had a lot of warm dust around it – which must have been heated by an outburst.
And when they compared WISE data with Spitzer telescope data from 2007, which showed its brightness increasing a few hundred times in that three-year period, they reasoned CX330 was likely a young star that had been outbursting for several years.
"We tried various interpretations for it, and the only one that makes sense is that this rapidly growing young star is forming in the middle of nowhere," Britt says.
It launches "jets," or outflows of material that slam into and heat the gas and dust around it. Eventually the gas and dust becomes ionised – that is, electrons are stripped away – and the material falls even faster onto the star.
Most puzzling to astronomers, the region of star formation closest to CX330 is more than 1,000 light-years away.
"CX330 is both more intense and more isolated than any of these young outbursting objects that we've ever seen," says Space Telescope Science Institute in Baltimore astronomer and study co-author Joel Green.
"This could be the tip of the iceberg – these objects may be everywhere."
How did CX330 become so isolated? One idea is that it may have been born in a star-forming region and was kicked out into its present lonely pocket of the galaxy.
But this is unlikely, astronomers say. As CX330 is still very young – probably less than one million years old – and is still eating its surrounding disc, it must have formed near its present location.
"If it had migrated from a star-forming region, it couldn't get there in its lifetime without stripping its disk away entirely," Britt says.
Last viewed in August 2015, CX330 is still guzzling and outbursting. The team will keep tabs on it, including with future telescopes that could view it in other wavelengths of light.