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August 03, 2010
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Sharpest views of a colossal, violent, star
Aug. 3, 2009
Courtesy ESO
and World Science staff
Astronomers have captured the sharpest views
yet of the “supergiant” star Betelgeuse. The pictures reveal that the star
throws out a vast plume of gas almost as large as our Solar System and
has a gigantic bubble boiling on its surface, researchers say. An image of the supergiant star Betelgeuse obtained with ESO’s Very Large
Telescope by astronomer Pierre Dervella and colleagues. New techniques
allowed the team to obtain the sharpest ever image of Betelgeuse, even with Earth’s turbulent, image-distorting atmosphere in the way. The resolution is as fine as 37
milliarcseconds, roughly the size of a tennis ball on the International Space Station, as seen from the ground. The image is based on data obtained in
near-infrared light, through different filters. The field of view is about half an arcsecond wide, North is up, East is left.
(Courtesy ESO)
The findings provide clues to explain how mammoths such as Betelgeuse (pronounced BET-el-jooz) shed material at such a tremendous
rate, according to astronomers.
Betelgeuse — the second brightest star in the constellation of Orion, the Hunter — is a red supergiant, one of the biggest stars known, and almost a thousand times larger than our Sun. It is also one of the brightest stars known, emitting more light than 100,000 Suns.
Such extreme properties foretell the demise of a short-lived stellar king, astronomers say. With an age of only a few million years, Betelgeuse is already nearing the end of its life and is soon doomed to explode as a supernova. When it does, the supernova should be easily visible from Earth, even in broad daylight.
Red supergiants still hold several unsolved mysteries. One of them is just how these behemoths shed such tremendous quantities of material — about the mass of the Sun
every 10,000 years.
Two teams of astronomers have used the European Southern Observatory’s Very Large Telescope
at Cerro Paranal, Chile, and advanced technologies to examine the star. Their combined work suggests that answers
may well be at hand, the researchers said.
The first research team used techniques that allowed high enough resolution that a tennis ball could be seen on the International Space Station. “We have detected a large plume of gas extending into space from the surface of Betelgeuse,” said Pierre
Kervella from the Paris Observatory, who led the team.
This shows that the star’s outer layer “is not shedding matter evenly in all directions,” added
Kervella. Two mechanisms could explain this, he said. One assumes that the mass loss occurs above the polar caps of the giant star, possibly because of its rotation. The other possibility is that such a plume is generated above large-scale gas motions inside the star, known as convection — similar to the circulation of water heated in a pot.
To arrive at a solution, astronomers needed to probe the behemoth in still finer detail. To do this Keiichi Ohnaka from the Max Planck Institute for Radio Astronomy in Bonn, Germany, and his colleagues used interferometry, a technique that combines light from different instruments, in this case three 1.8-metre Auxiliary Telescopes of the Very Large Telescope.
The astronomers obtained observations as sharp as those of a giant, virtual 48-metre telescope. With such resolution, the astronomers were able to detect indirectly details four times finer still than the previous image—in other words, the size of a marble on the
International Space Station, as seen from the ground.
“We detected how the gas is moving in different areas of Betelgeuse’s surface,
the first time this has been done for a star other than the Sun,” said Ohnaka. The observations, he added, show that the gas in Betelgeuse’s atmosphere is moving vigorously up and down, and that these bubbles are as large as the star itself. The observations have led the astronomers to propose that these large-scale gas motions roiling under Betelgeuse’s red surface are behind the ejection of the massive plume into space.
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Astronomers have captured the sharpest ever views of the supergiant star Betelgeuse. The pictures reveal that the star has a vast plume of gas almost as large as our Solar System and a gigantic bubble boiling on its surface, researchers say. These discoveries provide important clues to help explain how mammoths such as Betelgeuse (pronounced BET-el-jooz) shed material at such a tremendous rate. Betelgeuse — the second brightest star in the constellation of Orion, the Hunter — is a red supergiant, one of the biggest stars known, and almost a thousand times larger than our Sun. It is also one of the brightest stars known, emitting more light than 100,000 Suns. Such extreme properties foretell the demise of a short-lived stellar king, astronomers say. With an age of only a few million years, Betelgeuse is already nearing the end of its life and is soon doomed to explode as a supernova. When it does, the supernova should be easily visible from Earth, even in broad daylight. Red supergiants still hold several unsolved mysteries. One of them is just how these behemoths shed such tremendous quantities of material — about the mass of the Sun in about 10 thousand years. Two teams of astronomers have used the European Southern Observatory Very Large Telescope and advanced technologies to examine the star. Their combined work suggests that an answer to the long-open mass-loss question may well be at hand, the researchers said. The first research team used techniques that allowed high enough resolution that a tennis ball could be seen on the International Space Station. “We have detected a large plume of gas extending into space from the surface of Betelgeuse,” said Pierre Kervella from the Paris Observatory, who led the team. This shows that the star’s louter layer “is not shedding matter evenly in all directions,” added Kervella. Two mechanisms could explain this, he said. One assumes that the mass loss occurs above the polar caps of the giant star, possibly because of its rotation. The other possibility is that such a plume is generated above large-scale gas motions inside the star, known as convection — similar to the circulation of water heated in a pot. To arrive at a solution, astronomers needed to probe the behemoth in still finer detail. To do this Keiichi Ohnaka from the Max Planck Institute for Radio Astronomy in Bonn, Germany, and his colleagues used interferometry, a technique that combines light from different instruments, in this case three 1.8-metre Auxiliary Telescopes of the Very Large Telescope. The astronomers obtained observations as sharp as those of a giant, virtual 48-metre telescope. With such resolution, the astronomers were able to detect indirectly details four times finer still than the previous image—in other words, the size of a marble on the ISS, as seen from the ground. “We detected how the gas is moving in different areas of Betelgeuse’s surface ― the first time this has been done for a star other than the Sun,” said Ohnaka. The observations, he added, show that the gas in Betelgeuse’s atmosphere is moving vigorously up and down, and that these bubbles are as large as the star itself. The observations have led the astronomers to propose that these large-scale gas motions roiling under Betelgeuse’s red surface are behind the ejection of the massive plume into space.