Study: Reserve fuel tank powers Type Ia supernovae

ACTON, Australia, May 20 (UPI) -- Researchers use Type Ia supernovae -- a type of powerful and extra long-lasting stellar explosion -- to measure vast distances across the expanding universe.

Now, astronomers believe they've uncovered the source of the longevity of Type Ia supernovae.

Astronomers at the Australian National University recognized the spectral signature of radioactive cobalt-57 in the afterglow of a Type Ia supernovae. Researchers believe the element is evidence of a reserve engine that powers the unique stellar explosions.

"It's exciting to work this out because there are conflicting theories about what causes Type Ia supernovae," Ivo Seitenzahl, a scientist at the ANU Research School of Astronomy and Astrophysics, explained in a news release. "It's curious to me that we still don't know exactly what these things are, even though they are so important for cosmology."

Researchers believe Type Ia supernovae are triggered when an influx of mass maxes out the capacity of an old white dwarf star. Pushed over its mass threshold, the white dwarf explodes as its carbon core ignites.

While previous theories suggested the explosion is spurred by a stellar collision, the new findings point to prolonged theft from a companion star as the true source of energy. The new observations also suggest Type Ia supernovae feature stars larger and heavier than previously predicted.

Cobalt-57 is a byproduct of fusion between carbon and oxygen. The amount of cobalt-57 serves as a proxy for gauging the size of the ignited core, and thus the size of the exploded star. The trace element can allow researchers to distinguish between a 1.1 and 1.4 solar mass explosion.

"It doesn't seem like a big difference, but it amounts to 100 times higher density in the core of the star, which means a lot more cobalt-57 is created," Seitenzahl said.

The researchers published their latest findings in The Astrophysical Journal.