Betelgeuse is one of my favourite stars. Firstly it is easily identifiable as part of the Orion constellation and secondly did you know that it is actually the destination star for the original Planet of the Apes novel (in French by the way!). But on a more serious note it is a  semiregular variable star located approximately 640 light-years from the Earth. It’s more formal name is Alpha Orionis, the second brightest star in the constellation Orion and the ninth brightest star in the night sky.

Betelgeuse, the red supergiant at the top of the constellation of Orion

Betelgeuse is a red supergiant, and one of the largest and most luminous stars known. If the star were at the center of our solar system its surface might extend out to between the orbits of Mars and Jupiter. Current belief is that it is only a few million years old and there is some debate that it might even go supernova within  the lifespan of the human civilization.

What is so cool is that recently using interferometry, an image has been created by an international team led by an astronomer of l’Observatoire de Paris. There are clearly two bright spots whose size is equivalent to the Earth-Sun distance and they cover a large fraction of the surface.  It is an indication of the presence of the convection phenomenon which is a transport of heat by moving matter in a star.

Betelgeuse: The surface of Betelgeuse in near infrared at 1.64 micron in wavelength, obtained with the IOTA interferometer. The image has been reconstructed with two different algorithms, which yield the same details, of 9 milliarcseconds (mas). The star diameter is about 45 milliarcseconds. Copyright 2010 Haubois/Perrin (LESIA, Observatoire de Paris

Usually, even with our most powerful telescopes, most stars are unresolved dots. But because Betelgeuse is so big, it can be resolved using interferometry. This uses a number of telescopes to collect light and adds them together in such a way that extremely small objects (based on distance) can be resolved. Stunning image.

Here is a size comparison. You can barely see the sun in the image below.

Sun vs Betelgeuse Size comparison