June 5, 2014
A Rare Type Of Supernova Seen In Observations From Spitzer Space Telescope
Brett Smith for redOrbit.com - Your Universe Online
A supernova occurs when a tiny white dwarf star detonates in a massive blast and a common class of these explosions, called Type Ia, occurs when two white dwarfs orbiting each other collide.
Based on observations taken from the Spitzer Space Telescope, NASA scientists have uncovered evidence of a much rarer Type Ia supernova scenario – when a white dwarf feeds off an aging giant, to the point of explosion.
According to a report submitted to The Astrophysical Journal, the newly-discovered remnant of this kind of supernova sits 160,000 light-years away in the Large Magellanic Cloud, a small galaxy near our own.
"It's kind of like being a detective," said study author Brian Williams, an astrophysicist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, in a recent statement. "We look for clues in the remains to try to figure out what happened, even though we weren't there to see it."
Scientists have mostly found supernova remnants that are the result of two white dwarf stars colliding – with one major exception: Kepler's supernova. Named after the famous astronomer who witnessed it as it happened in 1604, the supernova is thought to have been preceded by a white dwarf and a companion red giant star, based on evidence collected over the past decade.
"It's like Kepler's older cousin," Williams said, referring to the supernova known as N103B.
Like Kepler's supernova remnant, N103B also sits in a cloud of gas and dust that appears to have shed by an older companion star. In this theoretical scenario, the material shed by the larger star fuels an eventual explosion by the companion white dwarf. Scientists can confirm this scenario for 103B, partly due to the fact that there are no historical sightings of the 1,000-year-old supernova taking place.
"The region around the remnant is extraordinarily dense," Williams noted.
While the white dwarf-red giant pairing was thought to be the cause of all supernovas until recently, the NASA scientists said this type of supernova actually appears to be extremely rare. They added that the precise mechanism that triggers a supernova is still unknown.
Although scientists don’t know just what makes a white dwarf explode, a few researchers working in the United Kingdom have been able to recreate a supernova on a small scale. The recreation was part of a study looking to understand how cosmic turbulence may have boosted magnetic fields to the power seen in interstellar space.
According to a new report in the journal Nature Physics, the tiny supernova was recreated using specialized lasers in the Vulcan laser facility at the UK’s Science and Technology Facilities Council’s Rutherford Appleton Lab.
“Our team began by focusing three laser beams onto a carbon rod target, not much thicker than a strand of hair, in a low density gas-filled chamber,” said study author Jena Meinecke, an Oxford University graduate student.
The massive quantity of heat generated over a few million degrees by the laser caused the carbon rod to blow up, generating a blast that grew out through low-density gas.
“It may sound surprising that a table-top laboratory experiment that fits inside an average room can be used to study astrophysical objects that are light years across,” said study author Gianluca Gregori, a physics professor at Oxford University. “In reality, the laws of physics are the same everywhere, and physical processes can be scaled from one to the other in the same way that waves in a bucket are comparable to waves in the ocean. So our experiments can complement observations of events such as the Cassiopeia A supernova explosion.”