Infamously located in the armpit of Orion, cherry red Betelgeuse is some 1,400 times larger than the sun and one of the largest stars currently known. Just so you know, the size of Betelgeuse depends up the color or wavelength of light in which it’s photographed. This latest picture was made by the ALMA array in Chile, which examines the sky in “millimeter and submillimeter light” located just beyond the infrared end of the color spectrum. Millimeter light waves are about the size of raindrops. In visible light, the star appears a little smaller, about 900 times the sun’s size. I’m still impressed.
Big stars burn their fuel faster than little ones, the reason Betelgeuse is just 8 million years old and on the verge of becoming a supernova. Smaller stars live for many billions of years. The sun’s been around for about 5 billion years and has enough nuclear fuel for at least another 7 billion. When the day comes that Betelgeuse goes supernova, the explosion will shine at least as bright as the half-moon and be easily visible in daylight. I hope you’re around for it.
We see Betelgeuse in the late stage of its life, when it expands in size and at the same time expelling gas and dust into space at the prodigious rate of about one solar mass — that’s the mass of our sun — every 10,000 years! Material leaves the star through the vigorous up and down movements of giant bubbles of gas in the star’s atmosphere called convection. They’re powered by the tremendous heat rising up from inside the star’s core. The same process happens when you boil water in a pot.
In the new picture, ALMA observes the hot gas of Betelgeuse’s chromosphere, a layer of its atmosphere just above the star’s surface. Local differences in temperature here give the star an out-of-round appearance. With the European Very Large Telescope, astronomers have also found a huge bubble of blazing gas on the surface of Betelgeuse and a vast plume of gas and dust as large as the solar system ejected by the star.
Since it’s summertime, Betelgeuse is in the daytime sky, but will return at dawn in August. It’s fun to think that if Betelgeuse exploded as a supernova in summer, we’d still see shining brightly!