It has been considerably heavier than the Sun

Dec 3, 2009 07:50 GMT  ·  By

Astronomers term massive stars all of the celestial bodies that have a mass several times that of our Sun. These massive spheres of fire are capable of many things when they finally reach the end of their burning cycle, such as transforming into neutron stars, or even black holes. But, almost inevitably, when they run out of hydrogen – the chemical that supports their nuclear fusion reactions – they burst, in what is known as a supernova, Space reports.

A short while ago, while looking at the sky, astronomers discovered traces left behind by an extraordinarily powerful cosmic explosion, which they attributed to a star transforming into a supernova. But, as it stands, this could have only been possible if the star that caused it was extremely large, the most massive one ever discovered. Experts believe that it would take a celestial body of at least 200 times the mass of the Sun to cause the bright explosion. The supernova was later measured to be 50 to 100 times brighter than any other ever recorded.

The readings were made in 2007. The explosion “was much brighter, and it was bright for a very long time. We could observe this thing almost two years after it was discovered, where you normally don't see anything anymore,” researcher Paolo Mazzali, from the Germany-based Max-Planck Institute for Astrophysics, explains. In a new study published today, in the journal Nature, the team admits that the signature left behind by the star matches what theoretical astrophysicists predicted to be a pair-instability supernova.

“There were some doubts that they existed. There were severe doubts that stars that massive could ever form in the universe. Now we seem to be very sure that there was a star with 200 solar masses,” University of Bonn astronomer Norbert Langer, who was not a part of the new study, says. The thing about pair-instability supernovae is the fact that they can only be generated by very massive stars, When the behemoths reach the end of their lives, they exhaust helium and hydrogen fuel, and are left with a core mostly made of oxygen. Unlike other supernovae, they do not continue to burn until only iron remains.

Supermassive stars have the ability to generate such high-energy photons when they are left with nothing more than their oxygen cores, that they produce electrons, and their anti-matter counterparts, positrons, in pairs. Whenever matter and antimatter meet, they annihilate each other immediately, and release large amounts of energy in the process. As this reaction occurs, the pressure inside the star decreases, and it then collapses on itself, igniting the core. When the latter explodes, it leaves nothing behind, unlike smaller massive stars, which leave various structures as a testament of their existence.

“I was never a believer in very massive stars. Seeing something like this explode means these things exist. This is a fairly new development in the formation of stars,” Mazzali concludes.