Astronomers witness supernova crash into star

Chuck Bednar for redOrbit.com – @BednarChuck

While type Ia supernovae are commonly used to locate dark energy in the universe, their origins have remained somewhat mysterious. Astronomers know that this happen when a white dwarf explodes as part of a binary system, but know little about that second star.

The properties of that second star and how it ultimately triggers the explosion have been difficult to discern. However, new research by astronomers at the University of California, Santa Barbara reports that they observed a supernova crash into a companion star.

This collision resulted in the creation of an ultraviolet pulse or glow that revealed the size of the companion, and this could provide new clues into the origin of type Ia supernovae, the study authors explained. Their findings have been published in the journal Nature.

Type Ia supernovae occur when a white dwarf star gains matter from a binary companion and explodes, but the exact process through which this occurs remained unclear. One theory is that the supernova is the result of the merger of two white dwarf stars, while another says that a normal or giant companion star that could survive the explosion may be involved.

Type Ia supernovae origin theories: either/or, or both?

The UC Santa Barbara astronomers are members of the intermediate Palomar Transient Factory (iPTF), and they used instruments from their facility, NASA’s Swift satellite, and the Las Cumbres Observatory Global Telescope Network to monitor the supernova iPTF14atg, located 300 million light years away in the galaxy IC831.

Iair Arcavi, a postdoctoral fellow in physics, explained that the team was initially puzzled by the observations, as “hot, blue supernovae are not supposed to happen in old, dead galaxies, and yet, as our robotic telescopes gathered the data, we watched in amazement as the blue supernova morphed into a type Ia supernova.”

They continued to collect data about the supernova, finding that it had a slow-moving explosion and belonged to a subclass of Ia supernovae sometimes referred to as SN 2002cx-like. This is a group that could even be partially failed or incomplete explosions in which a fragment may be left behind following the explosion. When combined with previous studies, the findings seem to indicate that both theories of Ia supernovae formation could be true.

“No wonder we’ve been so confused for decades. Apparently you can blow up stars in two different ways and still get nearly identical explosions,” said UCSB physics faculty member Andrew Howell. Curtis McCully, a UCSB supernova team member who was not part of the latest study, added that the discovery was “exciting” because it reveals, “how differences in the progenitor stars relate to differences in the explosion.”

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