The smallest 'red dwarfs', low mass 'yellow dwarfs' such as the Sun, massive 'blue dwarf' stars weighing eight times more than the Sun, and the 300 solar mass star

Scientists have spotted what may be the heaviest star ever discovered — hundreds of times bigger than the sun.

The star, called R136a1, may once have weighed as much as 320 times the weight of our Sun.

Astrophysicist Paul Crowther said the  star — twice as heavy as any previously discovered — his now considerably smaller than it once was.

In fact it is burning itself off with such intensity that it shines with nearly 10 million times the brightness of the Sun.

The massive star was located at the centre of the Tarantula Nebula and may have been more than 300 times larger, and 10 million times brighter, than the Sun

'Unlike humans, these stars are born heavy and lose weight as they age,' said Professor Crowther, an astrophysicist at the University of Sheffield.

'R136a1 is already middle-aged and has undergone an intense weight loss program,  shedding a fifth of its initial mass over that time, or more than fifty solar masses.'

Owing to the rarity of these monsters, I think it is unlikely that this new record will be broken any time soon.'

The giant was identified at the centre of a star cluster in the Tarantula Nebula, a sprawling cloud of gas and dust drifting through one of the Milky Way's neighbouring galaxies.

The star was the most massive of several giants identified by Crowther and his team in an article in the Monthly Notices of the Royal Astronomical Society.

While other stars can be larger, notably the swollen crimson-colored ones known as red giants, they weigh far less.

If R136a1 replaced the Sun at the centre of our solar system, it would outshine our star by as much as the Sun currently outshines the Moon.

Surface temperatures can surpass 40,000 degrees Celsius (72,000 degrees Fahrenheit), seven times hotter than the sun.

They are also several million times brighter, a product of the fact that they tear through their energy reserves far faster than their smaller counterparts.

That also means that massive stars quickly shed huge amounts of material and burn themselves out in what are thought to be spectacular explosions.

'The biggest live only 3 million years,' Crowther said. 'In astronomy that's a very short time.'

Small lifespans are one of several reasons why these stars are so hard to find. Another is that they're extremely rare, forming only in the densest star clusters.

Astronomers also have a limited range in which to look: In clusters that are too far away it is not always possible to tell if a telescope has picked up on one heavyweight star or two smaller ones in close proximity.

Zooming in on a monster: Three images which shows how the astronomers zoomed in on the massive star, The cluster is seen in the bottom right section of the third image

In this case, Crowther's team re-examined previously known stars to see if they could find an accurate measurement of their weight.

The team reviewed archival data from the Hubble Space Telescope and gathered new readings from the European Southern Observatory's Very Large Telescope at Paranal in Chile.

Scientists who were not involved in the find said the results were impressive, although they cautioned it was still possible, although unlikely, that scientists had confused two very close stars for a bigger, single one.

'What they're characterising as a single massive star could in fact be a binary system too close to be resolved,' said Mark Krumholz, an astronomer at the University of California, Santa Cruz.

Crowther acknowledged that R136a1 could have a partner, but he said it was likely to be a much smaller star, meaning that its birth weight was still considerable — perhaps 300 solar masses instead of 320.