Betelgeuse close-up reveals dying star

One of the world's biggest telescopes has captured a vast plume of gas and a mammoth boiling bubble on a red supergiant star set to explode in "the blink of an eye," astronomically speaking.

Betelgeuse has been around for a few million years, but the star's extreme size and luminosity mean the end is nigh, probably a few thousand years away.

The second-brightest star in the constellation of Orion, Betelgeuse is almost 1,000 times bigger than the sun. Astronomers say if Betelgeuse were at the centre of our solar system, it would encompass Mercury, Venus, Earth, Mars and the main asteroid belt, almost reaching Jupiter's orbit.

A team of astronomers using the Very Large Telescope — which actually consists of four very large telescopes sitting side-by-side on a mountaintop in Chile — collected more than half a million images of the star in January.

Jan Cami, a professor at the University of Western Ontario in London, was a member of a team led by the Paris Observatory's Pierre Kervella, who travelled to Chile for two days of observations and got a good look at a gas plume almost as big as our solar system. They could also make out fainter traces that may be two additional plumes, Cami says.

As the Earth's atmosphere can cause distortion in the stellar images the telescope sees, the team deformed the telescope's mirror for brief periods of time, a technique called adaptive optics. To freeze the star's apparent motion, they also used a short exposure time and advanced image processing techniques.

Huge star gets its close-up

This is the first time astronomers have used this combination of techniques on the Betelgeuse star, Cami says.

Betelgeuse is so bright it can damage big telescopes, but the team blocked much of the star's light. They wanted to use the Very Large Telescope because it can show faint objects and fine detail with greater sharpness.

Another group led by Keiichi Ohnaka of the Max Planck Institute for Radio Astronomy in Bonn, Germany, used a different viewing technique to map the movement of gas on the star's surface.

Ohnaka's group combined the light from the Very Large Telescope with that of a smaller telescope 48 metres away to produce a sharper image than would normally be possible.

"They obtained an image as sharp as what they would get with a 48-metre telescope," Cami said.

That team discovered a bubble of rising gas that corresponds to the location of the plume.

"It's absolutely spectacular," Cami says of the combined observations.

Betelgeuse expected to go supernova

Cami specializes in the chemical composition of material surrounding stars. He used the data from the telescope to identify elements in the plume.

"We know one of the chemical components is cyanide, which was surprising because we wouldn't have expected it."

The most important finding, though, is that the shape of the plume showed that Betelgeuse and supergiant stars like it are losing mass asymmetrically.

"It might help us understand how long it will take before the star explodes," Cami says.

Betelgeuse is a "textbook example" of a star that will soon become a supernova, and the new observations help astronomers as they try to understand what leads to the celestial explosions.

Cami said Betelgeuse will likely explode within thousands of years, an extremely short span of time by astronomical standards.