Stars more than six times as massive as our Sun are called massive stars.A massive star has short lifespan than the Sun or other low-mass stars.Hydrogen in the core of a massive star is used up with a much fast speed
The sun may be the most massive object in the solar system — it contains 99.8 percent of the mass of the entire system — but on a stellar scale, it's really quite average. About half of all known stars are more massive; about half have less mass. At the top end of the scale, the most massive known star in the sky is R136a1, a star more than 300 times as massive as our sun. And it's not alone in dwarfing Earth's dominant star.
Born heavy
RMC 136a1, usually abbreviated as R136a1, lies about 163,000 light-years from Earth in the Tarantula Nebula. This massive star lies outside our galaxy; it's part of the Large Magellanic Cloud, one of the Milky Way's satellite galaxies.
Astronomers working at the Radcliffe Observatory in South Africa first identified a star cluster in 1960, naming it RMC 136. When the Hubble Space Telescope examined the system, it found that the cluster was made up of more than 200 extremely bright stars; the most massive one was named RMC 136a1.
R136a1 has an estimated mass of 315 solar masses, where a solar mass is equal to the mass of the sun. (Its mass when discovered was estimated at 265 solar masses, but further observations in 2016 with NASA's Hubble Space Telescope refined the original measurements.) Although this makes it the most massive known star, it was once even larger.
"Unlike humans, these stars are born heavy and lose weight as they age," Paul Crowther, a researcher at the University of Sheffield in England, told Space.com in 2010. "Being a little over a million years old, the most extreme star R136a1 is already 'middle-aged' and has undergone an intense weight loss program."
Although R136a1 is the most massive known star, it is not the largest, since it only stretches about 30 times the radius of our sun. The largest known star is UY Scuti, a hypergiant with a radius somewhere around 1,700 times larger than the sun. Its mass, however, is only 30 times that of our nearest star.
If R136a1 swapped places with the sun, it would outshine our closest star as much as the sun currently outshines the moon. Its powerful radiation would have serious consequences for Earth.
"Its high mass would reduce the length of the Earth's year to three weeks, and it would bathe the Earth in incredibly intense ultraviolet radiation, rendering life on our planet impossible," said Raphael Hirschi, a research team member from Keele University in England.