So you think you know what a red giant star looks like? Think again. For this is how Betelgeuse, a star that may be on the verge of exploding as a supernova, might really appear close-up to the human eye.  

How a churning Betelgeuse would look to the eye in a still from the movie. Credit: Dr Bernd Freytag/Centre de Recherche Astronomique de Lyon

The serene crimson ball seen in so many artists’ impressions is replaced by a violently churning mass, according to a video shown at the three-yearly gathering of the International Astronomical Union (IAU) in Beijing today. See the video itself below.

Popular image of a red giant, viewed from a planet. Credit: Wikipedia

French astronomer Pierre Kervella, of the Observatoire de Paris, showed the movie made by colleague Dr. Bernd Freytag of the Centre de Recherche Astronomique de Lyon. It is a high-speed portrayal of the bubbling behaviour of Betelgeuse over seven and a half years. The boiling surface of the star, which lies 640 light-years away from Earth, shows irregular hot and cool areas which change their intensity and shape over the months.

Betelgeuse is one of the brightest stars in the sky to the unaided eye, marking the armpit in Orion, and has long been known to vary in its brightness. Amateur astronomy groups around the world have recorded its changing brightness over many decades.

It is also one of the biggest and most luminous stars known, being nearly 1,000 times larger than the Sun and shining more than 100,000 times more brightly.

Betelgeuse is so big that if placed at the centre of our own Solar System it would fill a space as far out as giant planet Jupiter! But it is only a few million years old, much younger than our four billion-year-old Sun, and is set to blow itself apart any time in the near cosmic future in an explosion that would make it visible in broad daylight.

The French astronomers created this computer model of Betelgeuse to match observations made using some of the most powerful telescopes which can observe in very high resolution, including the Very Large Array in New Mexico or the Hubble Space Telescope (HST).

Astronomers from the Observatoire de Paris, led by Xavier Haubois, have previously used interferometry to combine telescope observations in the infrared and obtain an image of Betelgeuse showing bright “starspots” on its surface.

The star is so large that it is one of the few in the sky that can be seen as a disk using the HST. But in 2009, astronomers reported that Betelgeuse had actually shrunk by 15 per cent since they began checking its size in 1993. Also in 2009, Pierre Kevalla led a team using the European Southern Observatory’s Very Large Telescope (VLT) to detect a huge plume blowing off the surface of Betelgeuse.