A presumed supernova has been found to be something much rarer!

What is a supernova? A supernova is a star that suddenly increases in size and brightness, this is caused by an enormous explosion that ejects most of its mass. Basically, it is a stellar explosion. It occurs during the last stages of a massive stars ‘life cycle’.

Because it occurs at the end of a huge stars life, it means supernovas are rare, currently anyway, as more and more stars die out it’ll probably become more common. 

Presumed Supernova is Rarer Than We Thought

A presumed supernova has been found to periodic flaring, a much rarer process. A research team from the University of Hawaii, led by Anna Payne, discovered that this presumed supernova was periodic flaring originating from a black hole in another galaxy.

An Active Galactic Nucleus (AGN), in the centre of ESO-253-G003, erupts every 114 days or so. The eruption from the black hole gives off bursts of energy, which evidently tears of pieces of an orbiting star.

An AGN is a compact region at the centre of each galaxy. It is typically brighter than the rest of the galaxy. It emits large amounts of luminosity throughout the electromagnetic spectrum.

Although we don’t know for sure, the radiation emitted by an AGN is probably caused by mass being pulled in by the massive amount of gravity of this large black hole. 

This AGN is over 570 million light-years away, and on November 14 2014, scientists first discovered this phenomenon and named it ASASSN-14ko (ASASSN for All-Sky Automated Survey for Supernovae). 

What is ASASSN? ASASSN is a global network of 20 automated telescopes, they are headquartered at the Ohio state university.

The centre of the AGN is much brighter than would be expected, in fact, it produced more energy by itself than the combined effort of all of its stars, most likely due to gravitational and frictional forces, which would be heating up a disc of gas that has accumulated around the supermassive black hole. 

As the dust is slowly pulled in to the black hole, it would create random changes in the light radiating from the disc. 

Presumed Supernova is Rarer Than We Thought
Presumed Supernova is Rarer Than We Thought

While looking at a light graph of the star orbiting the black hole, the research team observed a series of 17 flares, all evenly spaced by approximately 114 days between each flare. After five days, each flare reachest its brightest moment, to dim at about the same rate. 

From this discovery, the researchers calculated that they should experience another burst/flare on the 17th of May 2020. Since then they have been able to foresee flares occurring on the 7th of September and the 26th of December that same year.  

They later utilised NASA’s Transiting Exoplanet Survey Satellite, also known as TESS, to look into a detailed timeline of a flare the occurred on the 7th of November 2018. They observed the flares emergence, the peak of its luminosity and its decent.

By using different measurements from a large variety of observatories, including TESS and ASASSN, they made a list of 3 different possibilities, of what could be causing the flares. 

The least likely of the three is that the interaction between two discs of two black holes, at the centre of the galaxy is causing these flares. Although research has concluded the galaxy does have 2 black holes, they are not orbiting close enough to produce such an effect.

The second scenario is that a star advancing on an inclined orbit, passes through the black holes disc. If this was the case they would expect asymmetrically formed flares, which would have been caused when the star would disturb the disc, on both sides of the black hole. 

The most likely reason is a partial tidal disruption, which is when an orbiting star gets too close to a supermassive black hole, when it has to release part of its mass. This means that every time it passes too close to the black hole, it releases an large quantity of gas equivalent to 3 Jupiters. The flare is then sent outwards as the gas is pulled in to the black hole.  

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