Two years after scientists watched the closest and brightest Type Ia supernova ever measured, a new study on the event demonstrates just how important the event was in establishing a standard for others like it.
Labeled SN 2011fe, the event was caught by the Palomar Transient Factory less than 12 hours after it blew up in the Pinwheel Galaxy in the Big Dipper, though it was so easy to see through binoculars that it was soon dubbed the "Backyard Supernova."
Major astronomical studies followed on its heels, analyzing its various features such as luminosity and colors as it rapidly brightened and then slowly faded away.
The international Nearby Supernova Factory (SNfactor), led by Greg Aldering of the U.S. Department of Energy's Lawrence Berkeley National Laboratory isn't finished with 2011fe, however. Along with his team, the scientist has now released a unique dataset based on 32 nights of repeated observations of the explosion with the SuperNova Integral Field Spectrograph (SNIFS) located on the University of Hawaii's 2.2-meter telescope on Mauna Kea.
The observations, which began two weeks before the supernova reached its peak, continued over three months after maximum light had passed.
"We'd never before seen a Type Ia supernova this early," says Aldering, a cosmologist in Berkeley Lab's Physics Division. "Our measurements showed how remarkably normal 2011fe is."
For this reason, SNfactory member Rui Pereira of the Institut de Physique Nucleaire de Lyon argues that the collected data will act as a "benchmark atlas for all future studies" of other Type Ia supernovae.
According to the scientists, Type Ia supernovae aren't so much standard candles as they are "standardizable." Graphs that chart changes in their level of brightness and spectral features over time, also known as their light curves, vary. However, due to the fact that timing and brightness are related, light curves can be stretched - or squeezed - to match the standard.
In this case, SN 2011fe's light curve falls right in the peak of the distribution or, as astrophysicists say, it has "stretch 1."
Rollin Thomas of Berkeley Lab's Computation a Research Division says was deeply involved in the 2011fe analysis. At the time the new data arrived from the telescope each night, he said he recalls repeating to himself, "please don't be peculiar, please don't be peculiar."
Sure enough, Thomas's wish on this particular star worked - not only did 2011fe look like a textbook case, but it passed important tests. Its brightness at different times could be accurately recorded by scientists because the distance to its home galaxy was independently measured and there was not dust to obstruct the line of sight or affect color or brightness.
As vanilla as it is, however, 2011fe's light curve doesn't match the leading computation models, however, none of which fit the SNfactory data.
Given the unavoidable uncertainties regarding supernovae, Aldering said that, to date, "it has been a little too easy to cobble data together, depending on what you think it should be."
With the SNfactory data in place, however, the scientist believes that's going to change.
"From now on, researchers wont' be able to arbitrarly tweak knobs on their models," he said.
Furthermore, the researchers argue, the 2011fe gold-standard atlas will help answer many longstanding question about Type 1a supernovae, such as the progenitors of these titanic thermonuclear explosion and the mechanisms of the explosions themselves.
This is possible Aldering said, due to the atlas' "unprecedented detail."
"We've never had data like this," he explained. "It's a dream opportunity to stimulate deeper thinking about these markers of expansion of the universe."