Washington, May 15 : An international team of astronomers has found the youngest known supernova remnant in the Milky Way, which will help in understanding how often supernovae explode in our galaxy.
A supernova remnant (SNR) is the material ejected by a supernova, the explosion at the end of the life of a star much more massive than the Sun. In our own Galaxy, there are about 250 known SNRs.
Now, the supernova remnant detected using observations made with the Very Large Array (VLA) radio telescope in the US and the orbiting Chandra X-ray observatory, has been found to be the youngest.
The astronomers estimated that the supernova explosion occurred about 140 years ago, making it the most recent in the Milky Way. Previously, the last known supernova in our galaxy occurred around 1680, an estimate based on the expansion of its remnant, Cassiopeia A.
The tracking of this object began in 1985, when astronomers, led by David Green of the University of Cambridge, used the Very Large Array to identify the remnant of a supernova explosion near the center of our galaxy.
Based on its small size, it was thought to have resulted from a supernova that exploded about 400 to 1000 years ago.
Twenty-two years later, Chandra observations revealed the remnant had expanded by a surprisingly large amount, about 16 percent, since 1985. This indicates the supernova remnant is much younger than previously thought.
That young age was confirmed in recent weeks when the Very Large Array made new radio observations. This comparison of data pinpoints the age of the remnant at 140 years - possibly less if it has been slowing down - making it the youngest on record in the Milky Way.
Besides being the record holder for youngest supernova, the object is of considerable interest for other reasons.
Finding such a recent, obscured supernova is a first step in making a better estimate of how often the stellar explosions occur. This is important because supernovae heat and redistribute large amounts of gas, and pump heavy elements out into their surroundings.
They can trigger the formation of new stars as part of a cycle of stellar death and rebirth. The explosion also can leave behind, in addition to the expanding remnant, a central neutron star or black hole.
"No other object in the galaxy has properties like this," said Dr Stephen Reynolds of North Carolina State University. "This find is extremely important for learning more about how some stars explode and what happens in the aftermath," he added.