Discovery of one of the youngest and smallest supernova remnants
11 September 2013: Two Indian scientists, Subhashis Roy from NCRA and Sabyasachi Pal from ICSP have recently discovered a supernova remnant named as G354.4+0.0 which is only a few hundred years old.
Supernova explosion occurs in the last stage of certain stars, when either a compact highly dense star known as white dwarf sucks matter from a companion star and thereby its mass exceeds 1.4 Solar mass (Chandrasekhar limit) resulting in its complete destruction; or the core of a massive star collapses that causes violent expulsion of the outer layer and the inner part forms a neutron star or black hole. After the explosion, the ejected stellar fragments move out at tremendous velocities which create shock and compress the surrounding interstellar gas in to a spherical shell around the site of explosion. This shell known as the supernova remnant expands in diameter with time and are seen in radio frequencies due to emission from relativistic electrons in the shell. The diameter of the shell serves as a predictor of its age. In the last 400 years, more than 10 supernova explosions are expected to have taken place in our Galaxy. However, only two of them are known.
Recently, the above two Indian scientists published in Astrophysical Journal (v 774, p150; 2013 Sep 10) their discovery of a 1.6' angular sized supernova remnant 5 degrees away from the Galactic center using Giant Metrewave Radio Telescope (GMRT) observations at 330 and 1420 MHz. This is the first time GMRT observations have led to the discovery of an young supernova remnant of age 100-500 years.