Astronomers discover most luminous supernova ever

Washington: A team of astronomers including renowned names like Benjamin Shappee, Nidia Morrell and Ian Thompson has discovered the most-luminous supernova ever observed. It is being called ASAS-SN-15lh.

Supernovae are violent stellar explosions and some of the brightest objects in the universe. Human records noting their existence date back nearly 2,000 years.

Within the past two decades a rare new category of super-luminous supernovae have been discovered, which shine one hundred to a thousand times brighter than the more-common supernovae.

It has been theorised that these super-luminous supernovae are powered by so-called magnetars, neutron stars with extremely powerful magnetic fields, with the magnetism providing the engine for the immense luminosity. According to this theory, the magnetic field's spin magnifies the energy of the explosion, increasing the luminosity.

The newly found super-luminous supernova was discovered by the All Sky Automated Survey for SuperNovae team (ASAS-SN. The only all-sky variability survey in existence, it is capable of finding normal supernovae out to about 350 million light years from Earth.

Shappee said that on June 14 2015, they spotted a newly occurring explosion in a galaxy of an unknown distance. Subsequent observations including those made at our Las Campanas Observatory by Nidia Morrell and Ian Thompson allowed the team to confirm the existence of the supernova ASAS-SN-15lh.

The supernova's spectra matched that of other hydrogen-poor super-luminous supernovae. But it wasn't until further follow-up was conducted that the study's lead author Subo Dong and the rest of the team realised how unusual the supernova is.

The researchers also determined that the galaxy where ASAS-SN-15lh formed is very atypical for a super-luminous supernova, which raises questions about how these types of supernovae form. Its host galaxy isn't the typical low-luminosity, star-forming galaxy where previous super-luminous supernova have been spotted. ASAS-SN-15lh's galaxy is, in fact, more luminous than our own Milky Way.

The study is published in the Journal Science.