There’s a new model which explains Type Ia supernova creation

Oct 27, 2012 15:31 GMT  ·  By
SNR 0509-67.5, the remnants of a Type Ia supernova in a composite of visible and X-ray light
   SNR 0509-67.5, the remnants of a Type Ia supernova in a composite of visible and X-ray light

Type Ia supernovae are the result of an exploding white dwarf star, the type of star our sun will end up as billions of years from now. Normally, white dwarfs are too small to cause the type of runaway reaction that would result in a supernova, so they need a catalyst.

There are two main theories on how Type Ia supernovae are created. In one, a white dwarf is paired with a regular, younger star.

The white dwarf, which is small, but hot and dense, draws in material from the younger star accreting mass until it grows heavy and hot enough to trigger a massive thermonuclear explosion, resulting in the supernova. This is called the "single-degenerate model."

In the second model, the "double-degenerate model" both the stars in the pair are white dwarfs which orbit each other, drawing ever closer until they merge and create the explosion.

Astronomer J. Craig Wheeler finds flaws in both models, for one, no observation of Type Ia supernovae has found the remnants of the second star in the system. In a new paper published in The Astrophysical Journal, he proposes a new model.

He believes that Type Ia supernovae are the result of a binary system containing a white dwarf and an "M dwarf," which Wheeler dubbs a "white widow system." Black widow systems contain a neutron star and a regular star that's being stripped of its material.

M dwarfs, or red dwarfs – though the two terms are not completely interchangeable, are the most common type of stars in the galaxy.

They're also the faintest and coolest, so faint that they can't be seen in the visible spectrum. This would explain why Hubble observations found no trace of the companion star. M dwarfs are too small and cool to be seen or they may have been completely swallowed up by the white dwarf before it exploded.