The US space agency NASa announced the discovery of the most recent supernova in our galaxy. The supernova has been discovered by tracking the rapid expansion of its remains, the supernova remnant G1.9+0.3

According to the astronomers, the supernova explosion occurred about 140 years ago, which makes it the most recent supernova in the Milky Way as measured in Earth's time frame.

The tracking of this object began in 1985, when astronomers, led by Green, used the Very Large Array to identify the remnant of a supernova explosion near the center of our galaxy.

Supernova remnants are caused when the debris thrown outwards by the explosion crashes into surrounding material, generating a shell of hot gas and high-energy particles that glows brightly in X-rays, radio waves and other wavelengths for thousands of years.

Initially it was believed that the supernova remnants 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.

In the case of G1.9+0.3 the material is expanding outwards at almost 35 million miles per hour, or about 5% the speed of light, an unprecedented expansion speed for a supernova remnant. Another superlative for G1.9+0.3 is that it has generated the most energetic electrons ever seen in a supernova remnant.

Astronomers regularly observe supernovae in other galaxies like ours. Based on those observations, researchers estimate about three explode every century in the Milky Way.

"We can see some supernova explosions with optical telescopes across half of the universe, but when they're in this murk we can miss them in our own cosmic backyard," said Stephen Reynolds of North Carolina State University in Raleigh, who led the Chandra study. "Fortunately, the expanding gas cloud from the explosion shines brightly in radio waves and X-rays for thousands of years. X-ray and radio telescopes can see through all that obscuration and show us what we've been missing."

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.

"If the supernova rate estimates are correct, there should be the remnants of about 10 supernova explosions that are younger than Cassiopeia A," said David Green of the University of Cambridge in the United Kingdom, who led the Very Large Array study. "It's great to finally track one of them down."