Astronomers have snapped a very detailed image of the outer atmosphere of the red supergiant Betelgeuse.
This star is the nearest red supergiant to Earth, easily visible to the unaided eye sitting on the top left shoulder of Orion the Hunter. Betelgeuse is about 1,000 times larger than our Sun and lies about 650 light years away from Earth.
Astronomers took a new image with the e-MERLIN radio telescope array operated from the Jodrell Bank Observatory in Cheshire. The image shows Betelgeuse’s atmosphere extending out to five times the size of the visual surface of the star. It also reveals two hot spots within the outer atmosphere and a faint arc of cool gas even farther out beyond the radio surface of the star. The arc of cool gas extends about as far away as Pluto is from our Sun.
The hot spots have a temperature of about 6,740 to 8,540 degrees Fahrenheit, which is much higher than the average temperature of the radio surface of the star and even higher than the visual surface. Dr. Anita Richards, from The University of Manchester, said they are not sure why the hot spots are so hot.
“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. Another is that the outer atmosphere is patchy and we are seeing through to hotter regions within,” said Richards, who is lead author of the paper published in Monthly Notices of the Royal Astronomical Society. “The arc of cool gas is thought to be the result of a period of increased mass loss from the star at some point in the last century but its relationship to structures like the hot spots, which lie much closer in, within the star’s outer atmosphere, is unknown.”
Scientists do not have a good grasp behind the mechanisms by which supergiants like Betelgeuse lose matter. However, they do know this process plays a key role in the lifecycle of matter, enriching the interstellar material from which future stars and planets form.
“Betelgeuse produces a wind equivalent to losing the mass of the Earth every three years, enriched with the chemicals that will go into the next generation of star and planet formation,” said Dr. Richards, who is based in Manchester’s School of Physics and Astronomy. “The full details of how these cool, evolved stars launch their winds is one of the remaining big questions in stellar astronomy.”