Supernova Gold Standard For Normal
June 19, 2013

Supernova Becomes ‘Gold-Standard’ Of Normalcy

Lee Rannals for - Your Universe Online

A group of astronomers has released a dataset based on 32 nights of repeated observations of supernova 2011fe, creating a "gold-standard" atlas for Type 1a supernovae.

Astronomers were able to catch supernova 2011fe just 12 hours after it exploded in the Pinwheel Galaxy in the Big Dipper. The supernova is easy to spot with binoculars, and has been nicknamed the Backyard Supernova. Researchers from the international Nearby Supernova Factory (SNfactory) released a unique dataset based on 32 nights of repeated observations of the supernova with the SuperNova Integral Field Spectrograph (SNIFS).

“We´d never before seen a Type Ia supernova this early," says Greg Aldering, a cosmologist in Berkeley Lab's Physics Division who led the study recently published in the journal Astronomy & Astrophysics. “Our measurements showed how remarkably normal 2011fe is."

Supernova 2011fe was first spotted by telescopes on August 23, 2011. The supernova, which sits 21 million light years away, reached its peak brightness back in September of the same year.

The astronomers believe their data will be a "benchmark atlas" for future observations of this type of supernovae. The new data shows that 2011fe not only looks like a textbook case, but it passes important tests, making it the perfect standard to compare other supernovae with. Its brightness at different times was accurately recorded because the distance to its home galaxy had been measured independently, and there was little or no dust in the line of sight to affect color or brightness.

"To date it has been a little too easy to cobble data together, depending on what you think it should be," Aldering said. “From now on researchers won´t be able to arbitrarily tweak knobs in their models."

This new "gold-standard" atlas will help scientists answer many questions about Type Ia supernovae, including the progenitors of these thermonuclear explosions and the mechanisms of the explosions themselves.

“The 2011fe observations can be used to test these models," says Aldering. “For 2011fe, the existing models of the double-degenerate scenario agreed best at some epochs, but the single-degenerate scenario was better at others. And for some epochs both agreed very poorly with the data, suggesting these models have a way to go."

Data from 2011fe also points to unburned carbon as characteristic of the spectrum of a normal Type Ia. The finding adds weight to one model known as "pure turbulent deflagration," compared to two-stage explosions that would eliminate most excess carbon.

“The SN 2011fe atlas offers unprecedented detail and a solid point of reference for Type Ia physics," Aldering said. "We've never had data like this. It's a dream opportunity to stimulate deeper thinking about these markers of the expansion of the universe."