The News:

Andrew Howell, formerly of the Physics Division at Lawrence Berkeley National Laboratory and now at the University of Toronto, and Peter Nugent, an astrophysicist with Berkeley Lab's Computational Research Division said in a report, which appeared in the September 21 issue of Nature, as lead authors that a Supernova called SNLS-03D3bb in galaxy 4 billion light years away, is found to be more than twice as bright as most Type Ia supernovae, has much less kinetic energy but startlingly appears to be half as massive as a typical Type Ia supernova. In other words, it simply has overgrown the famed Chandrasekhar Limit!

"Chandrasekhar's 1931 model of stellar collapse was elegant and powerful; it won him the Nobel Prize," says Nugent. "But it was a simple one-dimensional model. Just by adding rotation one can exceed the Chandrasekhar mass, as he himself recognized," he added.

The Background:

What is Chandrasekhar's limit?

The Chandrasekhar's limit was first discovered and calculated by the Indian physicist Subrahmanyan Chandrasekhar in 1930. It is stated as follows:

In theory, the greatest possible mass of a stable cold star, above which it must collapse and become a black hole is 1.4 times the mass of our Sun. In other words, it is the the largest mass a white dwarf can attain.

How it came about?

In 1930, Chandrasekhar as a young undergraduate, setting out to Cambridge, Britain from India in pursuit of higher studies, calculated this remarkable thing on ship on his maiden voyage! There are many remarkable things about his work as is a heart rending controversy.

First, he applied Einstein's special theory of relativity to his study of the end stage in evolution of stars, when it is still not comprehended by many scientists. Even the renowned physicist, Stephen Hawking, hailed as ‘Second Einstein’, gave an account of Subramanian Chandrasekhar’s work in his classic popular science bestseller “A Brief History of Time”.

Second, his work predicted the existence of a stellar phenomenon that is simply fascinating, despite not being characterised further by him. His papers on the field are published between 1931 and 1936.

Now comes the pinching fact that when Chandrasekhar eventually presented this work in a Royal Society meeting in 1935, it was ridiculed and put down by Arthur Eddington, a scientist of reckoning in those days. The prejudice driven approach by Eddington and others embittered him and eventually left to the United States and remained there at the University of Chicago for the rest of his career.

Thanks to Arthur I. Miller, his novel "Empire of the Stars" gives a moving account of these things. Later, many scientists agreed with the opinion that the autocracy of Eddington might have delayed the progress of astrophysics by some 1 or 2 decades!

What happened now?

Scientists have found that the supernova is brighter but puzzlingly the ejecta of supernova are slower than typical Type Ia supernovae. This led to the conclusion that the supernova is resulted from a white dwarf star, that has super Chandrasekhar Limit mass. This does not mean the Limit is challenged yet. There are many possibilities. One, It's possible that a very rapidly spinning star could afford to be more massive without explosion. It's also possible that two white dwarfs, with a combined mass well over the Chandrasekhar limit, could collide and explode. Nevertheless, scientists warn that others should be careful when incorporating the Chandrasekhar limit in their work.

The heat of nuclear fusion in a star's core pushes the outer shells of the star outward against collapsing under gravity. As the star dies, the thrust vanishes and the star collapses back into its own core under its own gravity. At this stage, the electron degeneration starts and exerts pressure against collapse. If the star has a mass below the Chandrasekhar limit, this collapse is countered by electron degeneracy pressure and a stable white dwarf is born. If a star had a mass above the Chandrasekhar limit, the electron degeneracy pressure would be unable to resist the force of gravity, and collapse would ensue. The star's density would increase far beyond that of a white dwarf, leading to formation of a neutron star, black hole.