Scientists spot brightest supernova yet, twice as luminous

“ASASSN-15lh is the most powerful supernova discovered in human history”, said study lead author Subo Dong, an astronomer and a Youth Qianren Research Professor at the Kavli Institute for Astronomy and Astrophysics (KIAA) at Peking University. At its peak intensity, ASASSN-15lh was 570 billion times brighter than our own sun or 20 times brighter than the output of all 100 billion stars in the Milky Way galaxy.

When massive stars die, they do not go gently into the night.

The brightest supernova ever seen has been confirmed, but it still has astronomers puzzling over what unknown type of star could have been responsible. In fact, it’s twice as bright as the previous record-holder.

The huge blast, reported in the journal Science, is at the very upper limit of researchers understanding of stellar physics, raising new questions about how such a powerful event could be generated.

The exploding star was first observed back in June past year but is still radiating vast amounts of energy.

It could be a star massive enough that its core had already collapsed into a magnetar, a super-powerful kind of neutron star that radiates an intense magnetic field.

There’s an object about 10 miles across in the middle of the ball of gas that astronomers are trying to define. But no matter what is found, it’s clear that ASASSN-15lh is shining way more light on how astronomers observe the cosmos. But ASASSN-15lh is so potent that this compelling magnetar scenario just falls short of the required energies. By examining this bright, slowly fading afterglow, astronomers have gleaned a few basic clues about the origin of ASASSN-15lh.

The energy from that fast rotation is the engine that powers the supernova.

To produce a supernova as bright as ASASSN-15lh, almost all of the the magnetar’s energy has to be converted into light. It’s at the limit of what’s even physically possible.

However, as team leader Krzysztof Stanek from Ohio State, remarks “If it really is a magnetar, it’s as if nature took everything we know about magnetars and turned it up to 11”.

Dong and colleagues immediately put out word about the sighting of ASASSN-15lh in order for as much data as possible to be gathered. “Most of the elements in the world around us that are not hydrogen or helium were either created in supernovae explosions or distributed by them”.

One theory is that a type of extremely dense star, called a neutron star, is at the source of it all.

Potentially, it could just be a ridiculously massive star that exploded, because heavier stars appear to generate brighter supernovas, the researchers said. ASASSN-15lh is one of 180 supernovae discovered by ASAS-SN in 2015, and one of 270 discovered by the project since its start two years ago. “I am sure that in the near future, we will understand it much better”, Dong said. It is way hotter, and not just brighter, than its apparently nearest of supernova kin.

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.

This uses a suite of Nikon long lenses in Cerro Tololo, Chile, to sweep the sky for sudden brightenings.

Johannes Kepler claimed the discovery of the last supernova in our galaxy visible to the naked eye, in 1604.

Instead, it could be a sign of “unusual nuclear activity around a supermassive black hole”, said a statement by Ohio University.

“If it turns out to be wrong, in some sense it’s even cooler”, Stanek says.

“The most important thing is going to be to get the spectra of it as it fades, because as it fades, it’s getting cooler and bigger, and its luminosity is dropping”, says Thomspon. Gamma ray bursts, for example, are much more energetic and luminous. “This is because it’s so far away”. The current frontrunner is that they’re magnetars run amok. The problem is that we’ve seen these events before, and they don’t look like ASASSN-15lh.