Using the VISIR instrument on the European Southern Observatorys Very Large Telescope VLT, astronomers have imaged a complex and bright nebula around the supergiant star Betelgeuse in greater detail than ever before. This structure, which resembles flames emanating from the star, is formed as the behemoth sheds its material into space.
Betelgeuse, a red supergiant in the constellation of Orion, is one of the brightest stars in the night sky. It is also one of the biggest, being almost the size of the orbit of Jupiter — about four and half times the diameter of Earths orbit. The VLT image shows the surrounding nebula, which is much bigger than the supergiant itself, stretching 60 billion kilometres away from the stars surface — about 400 times the distance of Earth from the Sun.
Red supergiants like Betelgeuse represent one of the last stages in the life of a massive star. In this short-lived phase, the star increases in size, and expels material into space at a tremendous rate — it sheds immense quantities of material about the mass of the Sun in just 10,000 years. The process by which material is shed from a star like Betelgeuse involves two phenomena. The first is the formation of huge plumes of gas although much smaller than the nebula now imaged extending into space from the stars surface, previously detected using the NACO instrument on the VLT.
The other, which is behind the ejection of the plumes, is the vigorous up and down movement of giant bubbles in Betelgeuses atmosphere — like boiling water circulating in a pot. The new results show that the plumes seen close to the star are probably connected to structures in the outer nebula now imaged in the infrared with VISIR. The nebula cannot be seen in visible light, as the very bright Betelgeuse completely outshines it. The irregular, asymmetric shape of the material indicates that the star did not eject its material in a symmetric way. The bubbles of stellar material and the giant plumes they originate may be responsible for the clumpy look of the nebula.