New Delhi, Oct. 19: Two Indian astronomers have spotted a young supernova, a puzzlingly rare early stage of the cataclysmic explosion of a dying star while its ejected high-speed blast debris is still expanding far into space.
The supernova discovered by Subhashis Roy at the National Centre for Radio Astronomy, Pune, and Sabyasachi Pal at the Indian Centre for Space Physics, Calcutta, is only the third such object hitherto catalogued in the galaxy.
Their observations suggest that the supernova, lying close to the central region of the Milky Way galaxy and detected through its radio emissions, is less than 500 years old, one of the youngest-known remnants of a supernova.
The researchers used India’s Giant Metrewave Radio Telescope (GMRT) near Pune to study radio emissions from high-energy electrons in the expanding shell-like structure that marks the outer boundary of the ejected stellar debris. The scientists have described their finding in The Astrophysical Journal.
“The radius of the shell is about four light years across,” Roy told The Telegraph. “This tells us that the radio emissions we’re seeing today were emitted by the shell when it was only a few hundred years old.”
But scientists caution that the supernova is so distant that its light or radio waves would take at least 15,000 years to reach the Earth.
The supernova is not visible through optical telescopes. “A supernova eruption can be seen on optical wavelengths for only a few days to weeks,” Pal told this newspaper. “Then it fades away, but its remnants continue to emit radio waves and, at times, X-rays.”
The global astronomy community has thus far catalogued about 270 supernovas in the galaxy, a number far lower than what astronomers expect. Astronomers estimate that two to three supernova explosions occur every 100 years in the Milky Way.
“Over a 400-year period, we’d expect to see eight to nine young supernova remnants,” Roy said. “But until this new find, there were only two other young supernova less than 500 years old.”
The supernova, Cassiopia-A, detected in the early 17th century, is estimated to be about 350 years old, and a supernova detected by a US astrophysicist in 2008 is estimated to be only 140 years old. Both are in the Milky Way galaxy.
The astronomers say their discovery demonstrates the GMRT’s potential to detect young supernova remnants. They are now hoping to use space telescopes to study X-ray emissions from the new supernova.