The new Type Iax supernova are much fainter than the regular ones

Mar 27, 2013 09:34 GMT  ·  By

Astronomers have discovered a new type of supernova explosion, one small enough that it hasn't been detected until recently. The new type of supernova, dubbed Type Iax, is the smallest kind of supernova known, mostly because the explosion doesn't completely destroy the star, as is the case with Type Ia supernovae.

Until now, there were two main types of supernova. Type II supernovae, or core collapse supernovae are created by stars 10 to 100 times larger than our sun, which become too big for the internal pressure to support them, as they run out of fuel, so they explode.

The second big type, Type Ia supernovae, are created by smaller white dwarfs which accumulate material from a companion star until, again, they become too large to sustain themselves.

In both cases, the star is completely destroyed. Not so with this new type. It's a minisupernova, still created by a white dwarf.

But in this case, the explosion only blows away part of the star, leaving the core intact. This accounts for the fact that Type Iax supernovae are 100 times dimmer than regular supernova.

So far, 25 of these supernova have been discovered. They're all part of a binary system where the companion star has burned through all of its hydrogen and is now fusing helium.

The white dwarf siphons helium from the companion star. As for what causes it to explode, there are two main ideas.

The companion star could ignite its outer layer of helium and the resulting shock wave could impact the white dwarf, causing it to explode as well. Alternatively, all the helium that accumulates on top of the white dwarf may cause pressure and detonate the white dwarf.

In either case, the explosion isn't big enough to completely destroy the white dwarf, most of the time.