Hubble Reveals the Nature of Supernova Progenitor Stars

For years, astronomers have been trying to figure out the nature of a progenitor star, a stellar object that eventually blew up as a supernova, in a nearby galaxy. While earlier studies failed, recent observations conducted with the NASA Hubble Space Telescope finally managed to shed some light on the issue.

According to experts, there are several scenarios that can lead to a supernova explosion. One such scenario occurs when a massive star reaches the end of its burning cycle, becomes unstable and sheds its atmosphere in a violent blast.

If the progenitor star is large enough, then its core can collapse onto itself to form a neutron star, a pulsar or a magnetar (both of which are special types of neutron stars) or even a black hole.

Recent Hubble investigations focused on the supernova remnant SNR 0509-67.5, which was determined in previous studies to be a Type Ia event. The object is now located about 170,000 light-years away, in the Large Magellanic Cloud, a dwarf galaxy orbiting the Milky Way.

But experts also know that a Type Ia supernova usually occurs in binary systems, when material being pulled off a companion star makes its way to the surface of a white dwarf. In time, the amount of matter this object can hold without becoming unstable is exceeded.

The white dwarf then blows up in a huge thermonuclear explosion, which helps it reach equilibrium again. What puzzled investigators was that they could not find companion star for SNR 0509-67.5's progenitor, which was interpreted until now as meaning that the standard Type Ia model did not apply.

“We know Hubble has the sensitivity necessary to detect the faintest white dwarf remnants that could have caused such explosions,” explains astronomer and lead study investigator Bradley Schaefer, who is based at the Louisiana State University (LSU), in Baton Rouge.

“The logic here is the same as the famous quote from Sherlock Holmes: 'when you have eliminated the impossible, whatever remains, however improbable, must be the truth',” the expert goes on to explain.

What the Hubble research suggests is that the original binary system was made up of two white dwarfs, which spiraled closer and closer to each other until they merged and blew up. This can explain why no signs of a companion star can be found today.

Details of the research effort were published in the January 12 issue of the top scientific journal Nature.

Astronomers now plan to conduct additional investigations on supernova remnants in the Large Magellanic Cloud, simply because the galaxy is located so close to the Milky Way, and can be viewed with little trouble.