Supernova Reveals How the Biggest Stars in the Universe Die

/ Source: Space.com
Supernova
A brilliant supernova (right) explodes in the galaxy UGC 9379, located about 360 million light-years from Earth, in this before-and-after view.Alex Filippenko

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The most massive and luminous stars were long suspected to explode when they die, and astronomers now have the most direct evidence yet that these cosmic behemoths go out with a bang.

These findings shed light on the star explosions that provide the universe with the ingredients for planets and life, the researchers added.

Supernova
A brilliant supernova (right) explodes in the galaxy UGC 9379, located about 360 million light-years from Earth, in this before-and-after view.Alex Filippenko

With a mass more than 330,000 times that of Earth, the sun accounts for 99.86 percent of the solar system's total mass. But as stars go, the sun is a lightweight. The largest and most luminous stars in the universe are Wolf-Rayet stars, which are more than 20 times as massive as the sun and at least five times as hot. Only a few hundred of these titan stars are known to astronomers.

Astronomers long suspected that Wolf-Rayet stars violently self-destructed as supernovas, the most powerful stellar explosions in the universe. These outbursts are bright enough to momentarily outshine their entire galaxies, and enrich galaxies with heavy elements that eventually become the building blocks for planets and life.

However, the gigantic amounts of matter these stars blow out usually obscure them completely, so scientists weren't sure how they form, live and die.

By surveying the sky with the intermediate Palomar Transient Factory (iPTF), a project that charts the sky with a telescope mounted with a robotic observing system, the researchers discovered the Type IIb supernova very soon after it happened.

The explosion ionized surrounding molecules in an ultraviolet flash, giving them an electric charge. The ionized material that surrounded the star emits light that "tells us the elemental composition of the wind, and hence the surface composition of the star as it was just before it exploded," Gal-Yam said.

This light suggested the precursor of the supernova was a nitrogen-rich Wolf-Rayet star.

"This is the smoking gun," Nugent said. "For the first time, we can directly point to an observation and say that this type of Wolf-Rayet star leads to this kind of Type IIb supernova."

- Charles Q. Choi, Space.com

This is a condensed version of a story that appeared on Space.com. Read the entire story here. Follow us @Spacedotcom, Facebook or Google+.

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