Evan Ackerman
(dvice)
(dvice)
NASA, for some reason that the agency has chosen not to share, is quite interested in just exactly what it takes to set off a Type Ia supernova. Thanks to a series of X-ray and ultraviolet observations from the SWIFT satellite, NASA says that “we have a clearer picture of what’s required to blow up these stars.” Oh, good.
Type Ia supernovae are a specific type of stellar explosion that are very, very important because astronomers can use them as what’s called “standard candles.”
Standard candles (there are only a few different kinds and they’re all very rare) are things that we can see with a telescope and know how far away they are. Usually, if you see something through a telescope, there’s no reliable way of knowing whether it’s a bright thing that’s far away or a dim thing that’s up close. A standard candle has a luminosity (or, an intrinsic brightness) that doesn’t ever change, so based on how bright or dim it looks to us here on Earth, we can figure out how far away it (and everything around it) actually is.
With Type Ia supernovae, the standard candle is a white dwarf star that blows up. We know a fair amount about white dwarfs themselves: they’re main-sequence stars (like our sun) that have used up all of their fuel and collapsed into a white blob about the size of the Earth, glowing thanks to stored-up leftover heat. Made up mostly of carbon and oxygen, white dwarfs can’t undergo fusion on their own, so they just sit there and slowly cool off until eventually they stop putting out any light at all.
Sometimes, though, a white dwarf will have a companion star, as part of a binary system. And though the white dwarf is very small for a star, it still has star-like gravity, and it’ll start sucking up material from its companion.
