Supernovae are some of the brightest events that happen in space. However, in recent decades scientists have discovered a rare new class of blasts known as superluminous supernovae (SLSNe), or “hypernovae” to some. The new discovery was spotted last June by the All Sky Automated Survey for SuperNovae (ASAS-SN). At its peak, the new supernova known as ASAS-SN-15lh outshone our entire Milky Way galaxy by 50 times.
Captured by a system of eight small 14-centimeter telescopes that scan the entire sky every two to three days, ASAS-SN-15lh was twice as luminous as anything previously known, and thousands of times brighter than a normal supernova.
“ASASSN-15lh is the most powerful supernova discovered in human history,” said the study’s lead author Subo Dong, a Youth Qianren Research Professor at the Kavli Institute for Astronomy and Astrophysics (KIAA) at Peking University, in a statement. “The explosion’s mechanism and power source remain shrouded in mystery because all known theories meet serious challenges in explaining the immense amount of energy ASASSN-15lh has radiated.”
ASASSN-15lh is making some scientists scratch their heads. ASAS-SN-15lh appears to fall into a class called a hydrogen-poor SLSN, which theorists believe occurs when an old star runs out of fuel and creates a supernova blast while collapsing into a highly-magnetized neutron star, known as a magnetar. Furthermore, a magnetar is a rapidly spinning neutron star with a hugely powerful magnetic field that is created from the leftover, hyper-compressed core of a massive star that has exploded. As the theory goes, the magnetar powers up the still-expanding supernova making it unusually bright. But here’s the rub: this sort of SLSN is expected to form in small, dim dwarf galaxies full of young stars but ASAS-SN-15lh is in a large, bright galaxy with little star formation.
The images above is an artist’s impression of the record-breakingly powerful, superluminous supernova ASASSN-15lh as it would appear from an exoplanet located about 10,000 light years away in the host galaxy of the supernova. (Credit: Beijing Planetarium / Jin Ma)