Runaway stars create weird cosmic sculptures

January 8th, 2009 - 2:30 pm ICT by ANI  

London, Jan 8 (ANI): The Hubble Space Telescope has discovered 14 runaway stars speeding through dense interstellar gas, creating weird cosmic sculptures known as bow shocks.

Astronomers led by Raghvendra Sahai of NASAs Jet Propulsion Laboratory had been searching for ageing, bloated stars with Hubbles Advanced Camera for Surveys in 2005 and 2006, before the instrument failed permanently in 2007.

But, according to a report in New Scientist, when the researchers studied the images, they noticed 14 young stars that were shooting through interstellar gas, creating bow shocks in front of them that resemble the water waves created at the bow of a speeding boat.

The bow shocks form where particles streaming from the stars in stellar winds plough into surrounding gas.

When I first saw the images, I said, Wow, this is like a bullet speeding through the interstellar medium, Sahai said in a statement.

Similar bow shocks had been observed in the 1980s by the Infrared Astronomical Satellite. But, those bow shocks were much larger than the ones observed by Hubble, suggesting they were produced by more massive stars with more powerful stellar winds.

The stars in our study are likely the lower-mass and/or lower-speed counterparts to the massive stars with bow shocks detected by IRAS, said Sahai.

He added that low-mass stars outnumber their higher-mass counterparts, suggesting the newly found stars represent most of the universes stellar runaways.

The stars winds suggest they are just millions of years old, and their bow shocks suggest they are traveling through the interstellar gas at more than 180,000 kilometers per hour, about five times as fast as most young stars.

As to what accelerated them to such speeds, scientists cite one possibility as that the stars began their lives in pairs, but got boosted to high speeds when their partner exploded in a supernova.

Alternatively, the stars may have been involved in a gravitational run-in with two or three other stars and got kicked out in the process.

It is estimated that if they are just a million years or so old and are moving at about 180,000 km/h, they must have traveled about 160 light years from their birthplace.

The team plans to search for more such runaway stars and will also continue to scrutinize the existing Hubble observations to see if the stellar speedsters have much of an effect on the gas clouds they are traveling through, since turbulence can prevent gas clouds from condensing into new stars. (ANI)

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