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Superstar spreads its wings

Nebula surrounding Betelgeuse

A nebula surrounds the red supergiant star Betelgeuse. The nebula forms as the behemoth sheds material into space. The black disc corresponds to a very bright part of the image that was masked to allow the fainter nebula to be seen. Earlier observations of the heart of the nebula can be seen in the central disc.

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 gas into space.

Betelgeuse, a red supergiant in the constellation 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 the Earth’s orbit.

Hubble image of the surface of Betelgeuse

This image of Betelgeuse, released in 1996, was the first direct image of a star other than the Sun, and it was made with the Hubble Space Telescope. The image revealed a mysterious hot spot—more than ten times the diameter of Earth—on the stellar behemoth's surface.

The Very Large Telescope (VLT) image shows the surrounding nebula, which is much bigger than the supergiant itself, stretching 60 billion kilometres away from the star’s surface—about 400 times the distance of the 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 gas 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 processes. The first is the formation of huge plumes of gas (although much smaller than the nebula now imaged) extending into space from the star’s surface.

The other, which is behind the ejection of the plumes, is the vigorous up and down movement of giant bubbles in Betelgeuse’s atmosphere—like boiling water circulating in a pot.

Raw material for new planets

Earlier images using an instrument called NACO, revealed the plumes close in to the star. The new results show that those plumes are probably connected to structures in the outer nebula now imaged at infrared wavelengths with a different instrument, VISIR.

The nebula cannot be seen at visible light wavelengths, as the glare of Betelgeuse completely outshines it.

The irregular shape of the nebula 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.

The material visible in the new image is most likely made of silicate and alumina dust. This is the same material that forms most of the crust of the Earth and other rocky planets. At some time in the distant past, the silicates that eventually formed the Earth were expelled by a massive (and now extinct) star similar to Betelgeuse.

Adapted from information issued by ESO / P. Kervella / Andrea Dupree (Harvard-Smithsonian CfA), Ronald Gilliland (STScI), NASA and ESA.

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Orion’s hidden dimensions

WISE view of part of Orion

An infrared view of the region around The Hunter's head in the constellation Orion, taken by NASA's WISE infrared space telescope. The bright star at lower left is Betelguese.

IN GREEK MYTHOLOGY, Orion was a hunter whose vanity was so great that he angered the goddess Artemis. As his punishment, Artemis banished the hunter to the sky where he can be seen as the famous constellation Orion.

In the constellation, Orion’s head is represented by the star Lambda Orionis. When viewed in infrared light, NASA’s Wide-field Infrared Survey Explorer, or WISE, reveals a giant nebula around Lambda Orionis, inflating Orion’s head to huge proportions.

Lambda Orionis (1,060 light-years from Earth) is a hot, massive star that is surrounded by several other hot, massive stars, all of which are creating radiation that excites a ring of dust, creating the ‘Lambda Orionis molecular ring’.

Also known as SH 2-264, the Lambda Orionis molecular ring is sometimes called the Meissa ring. In Arabic, the star Lambda Orionis is known as ‘Meissa’ or ‘Al-Maisan,’ meaning ‘the shining one’. It is 1,470 light-years from Earth.

The Meissa Ring is of interest to astronomers because it contains clusters of young stars and proto-stars, or forming stars, embedded within the clouds.

With a diameter of approximately 130 light-years, the Lambda Orionis molecular ring is notable for being one of the largest star-forming regions WISE has seen.

This is also the largest single image featured by WISE so far, with an area of the sky approximately 10 by 10 degrees in size; equivalent to a grid of 20 by 20 full Moons.  Nevertheless, at less than 1 percent of the whole sky’s area, it is just a taste of WISE data.

Close up WISE view of Betelguese

Betelgeuse is a red supergiant star, approximately 600 light-years from Earth. It looks blue in this infrared view.

The Hunter’s female warrior friend

The bright blue star in the lower left corner of the image is Betelgeuse, which represents one shoulder of the hunter Orion. The name Betelgeuse is actually a corruption of the original Arabic phrase ‘Yad al-Jauza’ meaning ‘hand of the giant one’.

Betelgeuse (roughly 600 light-years from Earth) is well known for being a red supergiant star, yet in WISE’s infrared view it appears blue, as do most stars in WISE images. This is because most stars, including Betelgeuse, put out more light in the shortest infrared wavelengths of light captured by WISE, and those shorter wavelengths are presented in WISE images as blue and cyan.

In visible light, Orion’s other shoulder is clearly marked by the variable star Bellatrix (400 light-years from Earth). In infrared light, however, Bellatrix is a somewhat unremarkable cyan-coloured star in the right side of the image.

In Latin, Bellatrix means ‘female warrior,’ which is perhaps why the name was chosen for a female witch character in the popular Harry Potter books.

Also seen in this image are two dark nebulae, Barnard 30 and Barnard 35, which are parts of the Meissa ring that are so dense they block out visible light. Barnard 30 is the bright knob of gas and dust in the top centre part of the image. Barnard 35 appears as a hook extending towards the centre of the ring just above and to the right of the star Betelgeuse.

The bright reddish object seen to in the middle right part of the image is the star HR 1763, which is surrounded by another star-forming region, LBN 876.

Download a full-size (1.83M, 1600 x 1489 pixel) image here.

Adapted from information issued by NASA / JPL-Caltech / WISE Team.

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