Article Posted on : - Apr 22, 2011

WASHINGTON (BNS): Astronomers have always puzzled on why some of the tiniest galaxies produce some of the most massive stellar explosions in the Universe.

The data collected from NASA’s Galaxy Evolution Explorer offers to provide some clues in this regard.

Over the past few years, astronomers using data from the Palomar Transient Factory, a sky survey based at the ground-based Palomar Observatory near San Diego, have discovered a surprising number of exceptionally bright stellar explosions in so-called dwarf galaxies up to 1,000 times smaller than our Milky Way galaxy.

Stellar explosions, called supernovae, occur when massive stars – some up to 100 times the mass of our Sun – end their lives.

“It’s like finding a sumo wrestler in a little 'Smart Car,'” says Don Neill, a member of NASA’s Galaxy Evolution Explorer team.

The most powerful explosions of massive stars are happening in extremely low-mass galaxies, the researcher says.

Such low-mass galaxies also have low rates of star formation and do not produce many of the hefty stars.

Why then the massive stars undergo the most powerful explosions in little galaxies than their counterparts in large galaxies?

The new study explains that low-mass galaxies tend to have fewer heavy atoms, such as carbon and oxygen, than their larger counterparts. Since these small galaxies are younger, their stars have had less time to enrich the environment with heavy atoms.

The lack of heavy atoms in the atmosphere around a massive star causes it to shed less material as it ages. In essence, the massive stars in little galaxies are “fatter” in their old age than the massive stars in larger galaxies. And the fatter the star, the bigger the blast that will occur when it finally goes supernova.

This, according to the astronomers, may explain why “super supernovae” are occurring in the “not-so-super galaxies”.

The new findings appear in the Astrophysical Journal.