NASA spots one of the youngest-known supernova remnants

NASA’s Swift satellite has discovered one of the youngest-known supernova remnants — believed to be less than 2,500 years old — in our Milky Way galaxy.

The new object, discovered while performing an extensive X-ray survey of our galaxy’s central regions, has been designated G306.3-0.9 after the coordinates of its sky position, NASA said in a statement.

“Astronomers have previously catalogued more than 300 supernova remnants in the galaxy,” said lead scientist Mark Reynolds, researcher at the University of Michigan in Ann Arbor.

“Our analysis indicates that G306.3-0.9 is likely less than 2,500 years old, making it one of the 20 youngest remnants identified,” Reynolds said.

Astronomers estimate that a supernova explosion occurs once or twice a century in the Milky Way. The expanding blast wave and hot stellar debris slowly dissipate over hundreds of thousands of years, eventually mixing with and becoming indistinguishable from interstellar gas.

On February 22, 2011, Swift imaged a survey field near the southern border of the constellation Centaurus. Although nothing unusual appeared in the ultraviolet exposure, the X-ray image revealed an extended, semi-circular source reminiscent of a supernova remnant.

A search of archival data revealed counterparts in Spitzer infrared imagery and in radio data from the Molonglo Observatory Synthesis Telescope in Australia.

To further investigate the object, the team followed up with an 83-minute exposure using NASA’s Chandra X-ray Observatory and additional radio observations from the Australia Telescope Compact Array (ATCA), located near the town of Narrabri in New South Wales.

Using an estimated distance of 26,000 light-years for G306.3-0.9, the scientists determined that the explosion’s shock wave is racing through space at about 2.4 million km/h.

The Chandra observations reveal the presence of iron, neon, silicon and sulfur at temperatures exceeding 28 million C, a reminder not only of the energies involved but of the role supernovae play in seeding the galaxy with heavy elements produced in the hearts of massive stars.

“We don’t yet have enough information to determine what type of supernova this was and therefore what type of star exploded, but we’ve planned a further Chandra observation to improve the picture,” said co-author Jamie Kennea, a researcher at the Swift Mission Operations Center.

The findings will be published in The Astrophysical Journal.

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