Red Supergiant Betelgeuse Reveals Mysterious Hot Spots in New Image

A massive star named Betelgeuse burns about 650 light years away from Earth. Now, astronomers have released a new image of the star that's 1,000 times larger than our sun, revealing the detailed structure of the matter being hurled off of the red supergiant.

Betelgeuse itself is easily visible to the naked eye. If you look up at the constellation, Orion the Hunter, you can see the bright red star that creates the formation's shoulder. The star itself is what is known as a red supergiant, which means that it's part of a class of stars that are the largest in the universe in terms of volume.

The image was taken by the e-MERLIN radio telescope array, operated from the Jodrell Bank Observatory in Cheshire. It displays regions of surprisingly hot gas in the star's outer atmosphere and a cooler arc of gas weighing almost as much as the Earth. More specifically, the picture shows that the star's atmosphere extends out to five times the size of the visual surface; it also reveals two hot spots within the outer atmosphere.

The hot spots are separated by roughly half of the visual diameter of the star. At a fiery 4,000 to 5,000 Kelvin, they are at temperatures that are far higher than the visual surface, which is a more modest 3,600 Kelvin. The arc of cool gas is positively freezing in comparison--it's a mere 150 Kelvin.

What makes these temperatures so interesting is that researchers have been unable to explain exactly how hot spots actually become as hot as they do. There are theories, though.

"One possibility is that shock waves, caused either by the star pulsating or by convection in its outer layers, are compressing and heating the gas," said Anita Richards, the lead author, in a news release.  "Another is that the outer atmosphere is patchy and we are seeing through to hotter regions within."

The arc of cool gas, in contrast, is probably due to an increased loss of mass at some point in the last century. This loss of mass isn't usual for a red supergiant like Betelgeuse. In fact, every three years it produces a wind that's equivalent to losing the mass of Earth.

The findings could allow researchers to better understand hot spots and red supergiants. Researchers are planning future observations with e-MERLIN in order to test whether the hotspots vary in concert due to pulsation, or show more complex variability due to convection.

The findings are published in the journal Monthly Notices of the Royal Astronomical Society.