Monster Star Comes into Focus

Written by The Night Sky Guy on July 29, 2009 – 9:13 am -

Stars are so far away that most telescopes, even some of the largest, cannot resolve them into disks. They simply appear as a point of light. Now all that is changing, thanks to a new technique where the power of three giant telescopes can be combined as one.  Now astronomers have taken the sharpest view of a dying mammoth star ever made (see image on right).  Even with Earth’s turbulent, image-distorting atmosphere in the way, the resolution of the red giant Betelgeuse is as fine as 37 milliarcseconds, which is roughly the size of a tennis ball on the International Space Station (ISS), as seen from the ground.

For the first time they could show, how the gas is moving in different areas over the surface of a distant star. This latest news on the famous bright star, Betelgeuse, in the constellation Orion, comes on the heels of the discovery last month that the same star is skrinking in size. This new accomplishment was made possible by combining three 1.8 m telescopes as an interferometer, giving the astronomers the resolving power of a virtual, gigantic 48 m telescope. Using the ESO VLT Interferometer in Chile, they discovered that the gas in the dying star’s atmosphere is vigorously moving up and down, but the size of such “bubbles” is as large as the star itself. These colossal bubbles are a key for pushing material out of the star’s atmosphere into space, before the star explodes as a supernova.

Artists impression, showing how a vast amount of material is flung out from Betelgeuse into space.

Artist's impression, showing how a vast amount of material is flung out from Betelgeuse into space.

Betelgeuse in Orion

Betelgeuse in Orion

When one looks up the clear night sky in winter, it is easy to spot a bright, orange star on the shoulder of the constellation Orion (the Hunter) even in light-flooded big cities. That is Betelgeuse. It is a giant star, which is so huge as to almost reach the orbit of Jupiter, swallowing the inner planets Mercury, Venus, Earth, and Mars, when placed at the center of the solar system. It is also glaringly bright, emitting 100 000 times more light than the Sun. Betelgeuse is a so-called red supergiant and approaching the end of its short life of several million years. Red supergiants shed a large amount of material made of various molecules and dust, which are recycled for the next generation of stars and planets possibly like the Earth. As a matter of fact, Betelgeuse is losing material equivalent to the Earth’s mass every year.

The death of the mammoth star, which is expected in the next few thousand to hundred thousand years, will be accompanied by cosmic fireworks known as a supernova like the famous SN1987A. However, as Betelgeuse is much closer to the Earth than SN1987A, the supernova can be clearly seen with the unaided eye, even in daylight.

- Adapted from material taken from a news announcement by the Max-Planck-Institut for Radio Astronomy

click image to enlarge

click image to enlarge

Doorstep Astronomy: You can check out Betelgeuse and its host constellation Orion in the early morning sky. Look towards the eastern horizon about a half hour before local sunrise and you should be able to make out the belt of three stars and the distinct orange-hued Betelgeuse sitting to their upper left. If the glare from the dawn is giving you a hard time finding the red giant, then use the super-bright, star-like Venus (brightest star in the sky) and just scan over to its right side and you should see 429 light year distant Betelgeuse stand out.




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