Standard-candle supernovae are still standard, but why.
A new study shows that white dwarfs exploding as type Ia supernovae have a range of masses.
Type Ia supernovae result from the explosions of white dwarf stars.
Theoretical models (dashed black lines) seek to account for the differences, for example why faint supernovae fade quickly and bright supernovae fade slowly.
A new analysis by the Nearby Supernova Factory indicates that when peak brightnesses are accounted for, as shown in the upper graph, the late-time behaviors of faint and bright supernovae provide solid evidence that the white dwarfs that caused the explosions had different masses, even though the resulting blasts are all “standard candles.”
Sixteen years ago, two teams of supernova hunters, one led by Saul Perlmutter of the U.S.
The assumption was that carbon-oxygen white dwarf stars, the progenitors of the supernovae, capture additional mass by stripping it from a companion star or by merging with another white dwarf.
When they approach the Chandrasekhar limit (40 percent more massive than our Sun), they experience thermonuclear runaway.
“The Chandrasekhar mass limit has long been put forward by cosmologists as the most likely reason why type Ia supernovae brightnesses are so uniform, and more importantly, why they are not expected to change systematically at higher redshifts,” said Greg Aldering, who leads the international Nearby Supernova Factory (SNfactory) based in Berkeley Lab’s Physics Division.
“The Chandrasekhar limit is set by quantum mechanics and must apply equally, even for the most distant supernovae.”
But a new analysis of normal type Ia supernovae, led by SNfactory member Richard Scalzo of the Australian National University, shows that in fact they have a range of masses.
Most are near or slightly below the Chandrasekhar mass, and about 1 percent somehow manage to exceed it.
http://www.astronomy.com/news/2014/03/standard-candle-supernovae-are-still-standard-but-why
A new study shows that white dwarfs exploding as type Ia supernovae have a range of masses.
Type Ia supernovae result from the explosions of white dwarf stars.
Theoretical models (dashed black lines) seek to account for the differences, for example why faint supernovae fade quickly and bright supernovae fade slowly.
A new analysis by the Nearby Supernova Factory indicates that when peak brightnesses are accounted for, as shown in the upper graph, the late-time behaviors of faint and bright supernovae provide solid evidence that the white dwarfs that caused the explosions had different masses, even though the resulting blasts are all “standard candles.”
Sixteen years ago, two teams of supernova hunters, one led by Saul Perlmutter of the U.S.
The assumption was that carbon-oxygen white dwarf stars, the progenitors of the supernovae, capture additional mass by stripping it from a companion star or by merging with another white dwarf.
When they approach the Chandrasekhar limit (40 percent more massive than our Sun), they experience thermonuclear runaway.
“The Chandrasekhar mass limit has long been put forward by cosmologists as the most likely reason why type Ia supernovae brightnesses are so uniform, and more importantly, why they are not expected to change systematically at higher redshifts,” said Greg Aldering, who leads the international Nearby Supernova Factory (SNfactory) based in Berkeley Lab’s Physics Division.
“The Chandrasekhar limit is set by quantum mechanics and must apply equally, even for the most distant supernovae.”
But a new analysis of normal type Ia supernovae, led by SNfactory member Richard Scalzo of the Australian National University, shows that in fact they have a range of masses.
Most are near or slightly below the Chandrasekhar mass, and about 1 percent somehow manage to exceed it.
http://www.astronomy.com/news/2014/03/standard-candle-supernovae-are-still-standard-but-why
