Sunday, July 3

Thermonuclear blast sends star hurtling across our Milky Way

Researchers have found evidence of a star blasting itself out of its orbit with another star in a “partial supernova” — now hurtling across the Milky Way.

The star, which has about 40 percent of the mass of our sun, is traveling at 559,234 mph.

Scientists at the UK’s University of Warwick note that the star, a white dwarf designated SDSS J1240+6710, has an unusual composition. White dwarfs are very dense small stars that have exhausted their nuclear fuel.

“The majority of white dwarfs have atmospheres composed almost entirely of hydrogen or helium, with occasional evidence of carbon or oxygen dredged up from the star’s core,” the University of Warwick scientists explained in a statement. SDSS J1240+6710, however, seemed to contain neither hydrogen nor helium, but was composed instead of an unusual mix of oxygen, neon, magnesium and silicon, the researchers said.

Scientists were also able to identify carbon, sodium and aluminum using NASA’s Hubble space telescope. “However, there is a clear absence of what is known as the ‘iron group’ of elements, iron, nickel, chromium and manganese,” the researchers said, in the statement. “These heavier elements are normally cooked up from the lighter ones and make up the defining features of thermonuclear supernovae. The lack of iron group elements in SDSSJ1240+6710 suggests that the star only went through a partial supernova before the nuclear burning died out.”

The research is published in the journal Monthly Notices of the Royal Astronomical Society. Scientists from Brazil’s Universidade Federal do Rio Grande do Sul and Spain’s Universitat Politècnica de Catalunya were also involved in the project.

“This star is unique because it has all the key features of a white dwarf but it has this very high velocity and unusual abundances that make no sense when combined with its low mass,” said Professor Boris Gaensicke from the Department of Physics at the University of Warwick, in the statement. “It has a chemical composition which is the fingerprint of nuclear burning, a low mass and a very high velocity: all of these facts imply that it must have come from some kind of close binary system and it must have undergone thermonuclear ignition.”

The star would have been a type of supernova, but of a kind not seen before, Gaensicke added.

In a separate project, astronomers in Japan have spotted a huge “superflare” emerging from a nearby star.

Researchers at Kyoto University and the National Astronomical Observatory of Japan detected 12 stellar flares on AD Leonis, a red dwarf 16 light-years away. A light-year, which measures distance in space, equals about 6 trillion miles.

Red dwarf stars are the smallest and most abundant stars in our galaxy. They are also the longest-lived stars.