Astronomers have imaged the surface and atmosphere of a star that lies 550 light-years from Earth. It is the most detailed image of a star other than our own sun.

Antares is a red supergiant — about 700 times larger than our sun — that lies in the southern constellation of Scorpius. The star is in its death throes and shedding material into space. Eventually, it will explode as a brilliant supernova and will shine brightly in our night sky.

Red supergiants — stars that are more than 10 times more massive than the sun — are the largest stars in our universe, though they don't live long.

Using the European Southern Observatory's Very Large Telescope Interferometer (VLTI) at the Paranal Observatory in Chile, astronomers were able to map the star's surface and measure the motions of its surface material, giving them better insight into how the gases around a red supergiant move.

'What we see is just a mess, chaos.' - Keiichi Ohnaka, study's lead author

The telescope is a combination of four moveable, 1.8-metre telescopes that collect images taken in near-infrared wavelengths.

What they found was disorder.

"Antares is losing material not in a smooth or ordered way," lead author of the paper published in the journal Nature, Keiichi Ohnaka, told CBC News. "But the velocity maps show that it's very clumpy and turbulent and random. We don't know what the mechanism is behind this turbulent motion."

The image shows two brighter regions, which astronomers believe may be an area that has exposed the warmer gas below the surface of Antares.

VLTI velocity map of the surface of Antares

Astronomers constructed this map of the motions of material on the surface of Antares. This is the first velocity map (which measure speed of outflowing gas) of any star other than the sun. The red regions show material moving away from us, and the blue regions where the material is approaching. The empty region shows where measurements were not possible. (ESO/K. Ohnaka)

They believe that some clumps are energetic enough that they move faster and eventually escape the star. But the mapping doesn't answer all their questions.

"We still don't know what is really pushing the material, but at least we know how it's losing it," Ohnaka said.

'Opens a new window'

Now that the astronomers have shown that they are able to image distant stars (for the VLTI, they must be bright and somewhat large), they hope to move toward uncovering the mechanisms that drive the expulsion of gas in these dying stars, as it's so poorly understood.

"What we see is just a mess, chaos," Ohnaka said. This is what interests him the most and something he looks forward to exploring in depth.

Artist’s impression of red supergiant star Antares

This artist’s impression shows the red supergiant star Antares in the constellation of Scorpius. (ESO/M. Kornmesser)

Betelgeuse, a star in the constellation Orion with a radius 1,400 times that of our sun, is another red supergiant that is a ticking time bomb. While there's debate over exactly when it'll happen, it's anticipated that it will go supernova within a few thousand years, the blink of an eye in astronomical terms. 

Astronomers first produced an image of it in 2009. This June, the Atacama Large Millimeter/submillimeter Array (ALMA) telescope in Chile produced the highest resolution photograph ever.

If either of these stars goes supernova, they pose no threat to Earth.

Betelgeuse captured by ALMA

An image of Betelgeuse, taken by the European Southern Observatory's Atacama Large Millimeter/submillimeter Array (ALMA) in Chile in June 2017. (ALMA (ESO/NAOJ/NRAO)/E. O’Gorm)

Ohnaka said that they already have their next target: R Doradus, a star located in the constellation Dorado in the southern hemisphere. Unlike Antares, this star is similar to our own sun, which is too small to explode as a supernova. Instead, it will swell and turn into a red giant (not supergiant) and then expel most of its gases into space until it is a mere shell of its former self, a white dwarf.

"This new technique opens a new window to observe stars, like we observe the sun," Ohnaka said.