Talk about an explosive personality. Large galaxies usually have no more than three supernovas blow up in a century, but the nearby galaxy NGC 1316 has had two such explosions within the past 5 months and four in the past 26 years.
Amateur astronomer Berto Monard of Pretoria, South Africa, found both of the new supernovas. He reported the latest find in a Nov. 6 electronic telegram of the International Astronomical Union. After that announcement, Stefan Immler of NASA’s Goddard Space Flight Center in Greenbelt, Md., and his colleagues used NASA’s Swift satellite to view the two most recent stellar explosions. They unveiled their image Nov. 20. The team confirmed that like the earlier two NGC 1316 supernovas, the most recent ones belong to the class called type 1a.
While some researchers are puzzling over the supernova surplus, others propose a simple explanation. Supernovas of type 1a arise after a star that’s less than eight times the mass of the sun becomes a compact star called a white dwarf. If the dwarf siphons enough mass from a companion star, the accumulated material triggers a thermonuclear explosion, blowing the dwarf to bits. Astronomers have used type 1a supernovas to infer the presence of dark energy, a mysterious substance that has revved up the rate of expansion of the universe (SN: 11/18/06, p. 323: Available to subscribers at Dark Fingerprints: Hubble sheds light on cosmic expansion).
Hubble Space Telescope images have shown that NGC 1316, an elliptical galaxy lying 80 million light-years from Earth, has swallowed spiral galaxies, smashing together gas clouds and generating new massive stars. Several such mergers happened about 3 billion years ago, and there was a less powerful one a few hundred million years ago.
Amateur astronomer Berto Monard of Pretoria, South Africa, found both of the new supernovas. He reported the latest find in a Nov. 6 electronic telegram of the International Astronomical Union. After that announcement, Stefan Immler of NASA’s Goddard Space Flight Center in Greenbelt, Md., and his colleagues used NASA’s Swift satellite to view the two most recent stellar explosions. They unveiled their image Nov. 20. The team confirmed that like the earlier two NGC 1316 supernovas, the most recent ones belong to the class called type 1a.
While some researchers are puzzling over the supernova surplus, others propose a simple explanation. Supernovas of type 1a arise after a star that’s less than eight times the mass of the sun becomes a compact star called a white dwarf. If the dwarf siphons enough mass from a companion star, the accumulated material triggers a thermonuclear explosion, blowing the dwarf to bits. Astronomers have used type 1a supernovas to infer the presence of dark energy, a mysterious substance that has revved up the rate of expansion of the universe (SN: 11/18/06, p. 323: Available to subscribers at Dark Fingerprints: Hubble sheds light on cosmic expansion).
Hubble Space Telescope images have shown that NGC 1316, an elliptical galaxy lying 80 million light-years from Earth, has swallowed spiral galaxies, smashing together gas clouds and generating new massive stars. Several such mergers happened about 3 billion years ago, and there was a less powerful one a few hundred million years ago.
