Astronomers using a telescope in Chile have observed a hypergiant star shedding massive amounts of mass, suggesting it is about to end its relatively short life in a massive supernova explosion.

The red hypergiant star VY Canis Majoris, one of the largest stars ever found in the Milky Way, is losing enormous amounts of its mass as it deteriorates, they say.

It is 30 to 40 times as massive as our sun and 300,000 times as bright. If it sat in the center of our solar system, it would encompass the orbit of Jupiter.

"Massive stars live short lives," says study lead author Peter Scicluna of the Academia Sinica Institute for Astronomy and Astrophysics in Taiwan. "When they near their final days, they lose a lot of mass."

Scientists have long been unsure how that rapid shedding of mass is accomplished.

They say observations using an instrument known as Sphere on the Large Telescope at the European Southern Observatory may have provided an answer, by revealing a surrounding cloud of unexpectedly large dust grains 50 times larger than dust normally found between stars in interstellar space.

"These are big enough to be pushed away by the star's intense radiation pressure, which explains the star's rapid mass loss," explains Scicluna.

Radiation pressure is the force exerted by starlight, and is very weak, which is why only large dust grains have enough surface area to be affected and cause the star to lose mass, the researchers say.

VY Canis Majoris, around 3,800 light-years away from us, is expelling an amount of dust and gas every year equal to 30 times the mass of the Earth, they say.

Eventually, the hypergiant will explode in a massive supernova explosion, destroying much of the surrounding dust and flinging the rest into interstellar space along with heaver elements created in the supernova.

"This dust then contributes to the surrounding interstellar medium, feeding future generations of stars and encouraging them to form planets," the researchers say.

When that explosion occurs, likely hundreds of thousands of years from now, from the Earth, it could appear in the sky as bright as our moon, ESO scientists say.

The study of VY Canis Majoris has been published in the journal Astronomy & Astrophysics.