Supernova Mystery Solved

Type 1a supernova explosions are used by Astronomers as a standard candle for measuring distances in Astronomy.  They all explode with the same intrinsic brightness, and so depending on their apparent magnitude, ie how bright they look, we can determine the distance to them. It’s like a 40 watt light bulb.  No matter how far away I move it, it’s still 40 watts, even though it looks dimmer if it’s further away.  However, a few months ago some research came forward about type 1a supernova explosions, hinting that there may actually be two or more distinct types with slightly different properties.  This would make estimates of distances and our understanding of dark energy change, since those principles rely on our understanding of Type 1a Supernovae.

Supernova Explosion of a white dwarf hits a companion star in Blue. Credit: Daniel Kasen

However, even a discovery that changes our understanding is a step forward.  The distinct type 1a supernovae have given astronomers the ability to finally piece together the mysteries of these massive explosions. And to characterize their occurrence gives us a deep understanding of the behaviour of a star’s death.

For decades, the debate has been whether one white dwarf star, or two, leads to this massive explosion.  Finally, after years of research, the answer seems to be both!

The studies relied on a theory from physicist Daniel Kasen.  He suggested that the material ejected from a white dwarf star as it explodes will slam into a companion star and create a tell tale flash of ultraviolet light.  In the case of a single white dwarf, the companion star is necessary for the thermonuclear detonation of the white dwarf. The companion gradually loses material to the smaller star, causing it to eventually explode.  In the other case, two white dwarfs merge and undergo the thermonuclear detonation we call a supernova.

Understanding the behaviour of these two distinct supernova explosions will give new insights into the chemical enrichment of galaxies, the understanding of distances and structure in the universe, and the characterization of the elusive dark energy.

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