Extensive nebula frames Betelgeuse
by Amanda Doyle
for ASTRONOMY NOW
Posted: 23 June 2011
Astronomers using the VISIR instrument on the Very Large Telescope, which is operated by the European Southern Observatory, have produced an infrared photograph of a vast nebula surrounding the red supergiant star Betelgeuse.
The stunning infrared image of the vast plume emanating from the red supergiant Betelgeuse. The black disc in the centre is masking the brightest part of the star to reveal the details of the fainter surrounding nebula. Image: ESO / P. Kervella.
Betelgeuse is visible in winter skies from the northern hemisphere in the constellation of Orion, and if it were placed in our Solar System in the Sun's position, it would extend as far as the orbit of Jupiter, a swollen size that relates to its advanced stage of stellar evolution.
The new image comprises details from previous NACO observations, which are reproduced in the central disc where the small red circle in the middle has a diameter about four and half times that of the Earth’s orbit and represents the location of Betelgeuse’s visible surface, with new VISIR data taken at different infrared wavelengths. The blue regions correspond to short wavelengths and the red regions to longer wavelengths.
The plumes from the inner image seen close to the star are likely related to the structure detailed in the new image, that extend 60 billion kilometres away from the red supergiant – about 400 times the distance of the Earth from the Sun. Even further afield is a bow shock at a distance around 100 times that of the dust envelope, caused by the stellar wind of Betelgeuse interacting with the interstellar medium.
What really stands out is the asymmetrical shape of the dust envelope, showing that mass loss from Betelgeuse occurs in an irregular fashion. Also evident is what appears to be a partial shell, which is thought to be the inner region of the dust envelope. It will take gas between 30 and 60 years to migrate from the photosphere of the star to the inner region of the dust shell.
Betelgeuse has shed an amount of material similar to the mass of the Sun in about 10,000 years, which is flooding the interstellar medium with oxygen rich dust that will subsequently be used in new star formation.
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