Closest 'standard candle' supernova of nearby galaxy observed in decades

Less than 12 million light-years away, the Supernova 2014J in the nearby galaxy M82, which exploded on January 14, 2014, was the closest "standard candle" supernova in 42 years.

An impressive coordinated observational effort orchestrated by the intermediate Palomar Transient Factory (iPTF) team and led by Ariel Goobar from the Oskar Klein Centre at Stockholm University provides important new clues into the nature of these explosions, as well as the environments where they take place.

The proximity of SN2014J allowed the iPTF team to study this important class of stellar explosions, known as Type Ia supernovae, over a very wide wavelength range, starting just hours after the deduced explosion time.

Furthermore, Goobar and collaborators used pre-explosion images of the region of M82 where the supernova went off, both from the Hubble Space Telescope and from the Palomar Oschin Telescope, to search for a star in the location of the explosion, or possible earlier nova eruptions.

The lack of pre-explosion detections suggests that the supernova may have originated in the merging of compact faint objects, e.g., two white dwarf stars, i.e., the kind of Earth-size stars that our Sun will evolve to once it runs out of nuclear fuel.

"Until very recently, the leading model for standard candle supernovae was thought to include a companion star from which material was stripped by the white dwarf until the accumulated mass could no longer be sustained by the outwards pressure, leading to a runaway thermonuclear explosion. The observations of SN2014J are challenging for this theoretical picture," Goobar said.

Type Ia supernovae are among the best tools to measure cosmological distances. Thanks to their consistent peak brightness, these "standard candles" are used to map the expansion history of the universe.

The findings are published in The Astrophysical Journal Letters.