Universe’s biggest star discovered

LONDON - The biggest star, with a mass 320 times greater than the sun’s, has been discovered at the edge of our galaxy by British astronomers.

Scientists at the University of Sheffield found the stellar giant - named R136a1 - using the European Southern Observatory’s Very Large Telescope in Chile and data from the Hubble Space Telescope.

The star is located in the Tarantula Nebula in the Large Magellanic Cloud, a small “satellite” galaxy which orbits the Milky Way, the Telegraph reported.

Previously, the heaviest known stars were around 150 times the mass of the sun, and this was believed to be close to the cosmic size limit.

As stars get more massive, the amount of energy created in their cores grows at a faster rate than the force of gravity which holds them together.

The torrents of energy produced eventually become so powerful that the stars are torn apart, says the latest issue of Monthly Notices of the Royal Astronomical Society.

This is known as the “Eddington Limit”, after the British physicist Arthur Eddington who, in 1919, proved Einstein’s theory of relativity by showing that light is bent by gravity.

It was believed that the Eddington Limit was reached at around 150 solar masses.

However, R136a1 has been measured at 265 solar masses. Since heavy stars rapidly lose mass as they grow older by converting it into energy, R136a1 has already lost 20 percent of its mass in its short million-year life. It is believed originally to have been a colossal 320 solar masses.

The sun, by comparison, has been burning for 4.57 billion years, and has converted only 0.03 percent of its mass into energy.

The chief researcher and professor in the Sheffield team, Paul Crowther, told ‘Astronomy Now’: “Because of their proximity to the Eddington Limit they lose mass at a pretty high rate.”

This means that they are incredibly bright and hot - R136a1 is believed to have a surface temperature of more than 40,000 degrees Celsius, and is 10 million times brighter than the sun.

Among the largest known stars previously known were the Pistol Star, between 80 and 150 solar masses, and Eta Carinae, around 100 solar masses.

The Pistol Star radiates as much energy in 20 seconds as our sun does in a year. However, both are utterly dwarfed by the vast new discovery.

According to ‘Astronomy Now,’ R136a1 gives off more energy than all the stars in the Orion Nebula, and if it were in our solar system it would be as much brighter than the sun as the sun is than the moon.

Crowther suspects that this is about as big as stars can get. “Owing to the rarity of these monsters, I think it is unlikely that this new record will be broken any time soon,” he says.