London, Jan 12 (ANI): With the help of NASA's Hubble Space telescope, astronomers have finally solved a longstanding mystery on the type of star that caused a supernova seen in a nearby galaxy.
Based on previous observations from ground-based telescopes, astronomers knew the supernova class, called a Type Ia, created a remnant named SNR 0509-67.5, which lies 170,000 light-years away in the Large Magellanic Cloud galaxy.
Theoretically, this kind of supernova explosion is caused by a star spilling material onto a white dwarf companion, the compact remnant of a normal star, until it sets off one of the most powerful explosions in the universe.
They failed to find any remnant of the companion star, however, and concluded that the common scenario did not apply in this case, although it is still a viable theory for other Type Ia supernovae.
"We know Hubble has the sensitivity necessary to detect the faintest white dwarf remnants that could have caused such explosions," Bradley Schaefer, the principal investigator from of Louisiana State University (LSU) in Baton Rouge, said.
"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'," he said.
The cause of SNR 0509-67.5 can be best explained by two tightly orbiting white dwarf stars spiralling closer until they finally collided and exploded.
For four decades, the search for Type Ia supernovae progenitors has been a key question in astrophysics. The problem has taken on special importance during the last decade with Type Ia supernovae being the premier tools for measuring the accelerating universe.
Type Ia supernovae release tremendous energy, in which the light produced is often brighter than an entire galaxy of stars. The problem has been to identify the type of star system that pushes the white dwarf's mass over the edge and triggers this type of explosion.
Many possibilities have been suggested, but most require that a companion star near the exploding white dwarf be left behind after the explosion.
Therefore, a possible way to distinguish between the various progenitor models has been to look deep in the centre of an old supernova remnant to search for the ex-companion star.
In 2010, Schaefer and Ashley Pagnotta of LSU were preparing a proposal to look for any faint ex-companion stars in the centre of four supernova remnants in the Large Magellanic Cloud when they discovered the Hubble Space Telescope already had taken the desired image of one of their target remnants, SNR 0509-67.5, for the Hubble Heritage program, which collects images of especially photogenic astronomical targets.
In analysing the central region, they found it to be completely empty of stars down to the limit of the faintest objects Hubble can detect in the photos. Schaefer suggests the best explanation left is the so-called "double degenerate model" in which two white dwarfs collide.
The study has been recently published in the journal Nature. (ANI)
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