Astronomers working on a multi-year program with the Hubble Space Telescope have announced the discovery of the most distant Type Ia supernova ever observed, a stellar explosion that occurred over 10 billion years ago — breaking the previous record by nearly a billion years.
What’s especially important is the kind of supernova that’s been discovered. Designated SN UDS10Wil (and nicknamed SN Wilson after the 28th president of the United States) this distant detonation is a Type Ia — that’s “one-A” — supernova, the garden variety of which are used as standard candles by scientists to measure distances across the universe.
Calculating distance in intergalactic space from here on Earth isn’t easy. So in order to figure out how far away galaxies are, astronomers have learned to use the light from Type Ia supernovae, which briefly — but consistently — shine with a brilliance equal to 5 billion suns.
This method has proven useful for distances beyond our galaxy (they use different ways to measure space within the Milky Way) despite the fact that it’s not known exactly what kinds of stars create Type Ia supernovae in the first place. While it’s generally accepted that they are the result of the accumulation of matter between two stars in a binary pair until a critical mass is reached and a brilliant stellar explosion occurs, two different scenarios are currently on the table: one, that the pair consists of a white dwarf pulling matter from a swollen red giant partner, and two, the stars are both white dwarfs locked in orbit with each other, getting closer and closer until they eventually merge together and… boom. Supernova.
The discovery of supernova SN Wilson helps lend credence to the latter, if only because it’s so far removed from the previous record-holders. The steep drop-off in Type Ia supernovae between 7.5 and 10 billion years ago found by the three-year Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey (CANDELS) and the Cluster Lensing and Supernova Survey with Hubble (CLASH) surveys indicates the sheer amount of time needed for two white dwarfs — which are the final life stages of stars like our sun — to form within binary pairs and eventually merge.
“This new result is a really exciting step forward in our study of supernovae and the distant universe,” said team member Jens Hjorth of the Dark Cosmology Centre at the University of Copenhagen. “We can begin to explore and understand the stars that cause these violent explosions.”
And understanding Type Ia supernovae is more than just knowing how far things are away in space — it’s also knowing more about how the universe is expanding due to the outward pull of dark energy and also, ultimately, about where we came from. After all, it’s stellar explosions like these that seeded the universe with the sorts of heavy elements that make up our solar system, our planet, and ourselves.
The team’s results will appear in the May 10 issue of The Astrophysical Journal. Read more on ESA’s Hubble site here.