Closest-Ever Look At Betelgeuse Reveals its Fiery Secret
Written by Anne Minard
Artist’s impression of the supergiant star Betelgeuse as it was revealed with ESO’s Very Large Telescope. Credit: ESO/L.Calçada
The giant star Betelgeuse churns out gas bubbles that match its own size — and that's how it can shed an entire solar mass in 10,000 years.
That according to the sharpest-ever images of Orion's second-brightest star, released this week by the European Organisation for Astronomical Research in the Southern Hemisphere (ESO). At left is an artist’s impression of the supergiant star Betelgeuse as it was revealed in the new images (courtesy of ESO and L.Calçada). The actual images follow …
This collage shows the Orion constellation in the sky (Betelgeuse is identified by the marker), a zoom towards Betelgeuse, and the sharpest ever image of this supergiant star, which was obtained with NACO on ESO’s Very Large Telescope. Credit: ESO, P.Kervella, Digitized Sky Survey 2 and A. Fujii
Betelgeuse, the second brightest star in the constellation of Orion (the Hunter), is a red supergiant, one of the biggest stars known, and almost 1,000 times larger than our Sun. It is also one of the most luminous stars known, emitting more light than 100,000 Suns.
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 only 10,000 years.
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 seen easily from Earth, even in broad daylight.
Using ESO's Very Large Telescope, two independent teams of astronomers have obtained the sharpest ever views of the supergiant star.
The first team used the adaptive optics instrument, NACO, combined with a so-called “lucky imaging” technique, to obtain the sharpest ever image of Betelgeuse, even with Earth’s turbulent, image-distorting atmosphere in the way. With lucky imaging, only the very sharpest exposures are chosen and then combined to form an image much sharper than a single, longer exposure would be.
The resulting NACO images almost reach the theoretical limit of sharpness attainable for an 8-metre telescope. The resolution 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.
“Thanks to these outstanding images, 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. The plume extends to at least six times the diameter of the star, corresponding to the distance between the Sun and Neptune. “This is a clear indication that the whole outer shell of the star is not shedding matter evenly in all directions.”
Two mechanisms could explain this asymmetry. 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, Keiichi Ohnaka from the Max Planck Institute for Radio Astronomy in Bonn, Germany, and his colleagues used ESO’s Very Large Telescope Interferometer. The astronomers were able to detect details four times finer still than the NACO images had allowed — in other words, the size of a marble on the ISS, as seen from the ground.
“Our AMBER observations are the sharpest observations of any kind ever made of Betelgeuse. Moreover, 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," Ohnaka said.
The AMBER observations revealed that the gas in Betelgeuse's atmosphere is moving vigorously up and down, and that these bubbles are as large as the supergiant star itself. The astronomers are proposing that these large-scale gas motions roiling under Betelgeuse’s red surface are behind the ejection of the massive plume into space.
Source: European Organisation for Astronomical Research in the Southern Hemisphere (ESO). Two related papers are here and here.
Filed under: Astronomy
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July 29th, 2009 at 9:16 am
It would be fun to see this star go supernova sometime in my lifetime. My reaction would look something like this: O_o
July 29th, 2009 at 3:33 pm
roughly the size of a tennis ball on the International Space Station (ISS), as seen from the ground.
Not to put too fine a point on it, but the press officer who came up with this ought to be strangled slowly with his own tongue.
July 29th, 2009 at 4:51 pm
I always wondered what convection cells would look like on these huge low density stars, and kind of figured that if they existed they'd probably be impressively large.
Not for a second did I think that they'd be THAT large! Awesome finding.
Interesting that the NACO images combined the use of adaptive optics AND lucky imaging techniques. Now that is striving for resolution!
July 29th, 2009 at 11:24 pm
It's great to see the lucky imaging technique come of age. I saw some of the early work done by a team of Cambridge University astronomers and was amazed that such a simple technique could improve the resulting images by so much.
At the time, it seemed that LI would be limited to smaller scopes under certain viewing conditions — e.g. wide field observations, but apparently they have overcome these issues to make it work with one of the largest telescopes in the world!
Kudos to all involved.
July 30th, 2009 at 8:26 pm
I have conflicting information of the distance
of Betelgeuse to Earth? Is it 650LY or 450LY?
In any case I do believe that when this thing
turns SN. the effects will be felt in our solar
system and our planet in a verry destuctive way. It is highly probable that it may disturbe
the balance of our sector, to the point that we could be in a different trajectory? That is an sobering thought, but that is an worry for the next 4 generations if that soon.
August 1st, 2009 at 3:30 pm
Betelgeuse is located around 430 +/- 100 light-years from Sol (based on HIPPARCOS)
The supernova may be sooner than later. I saw an article dated JUL 09 stating that the star's diameter has shrunk 15% since 1993.
This may be due to an outbust (like above) or just better measurements. The outer surface is rather tenuous, so it may be hard to determine where the star's atmosphere "ends."
August 2nd, 2009 at 6:18 am
That article on 'shrinking Betelgeuse' appeared in a July 4, 2009 post in Science News and can be found here: http://www.sciencenews.org/index/generic/activity/view/id/44573/title/Betelgeuse_shrinks . The article mentions that the observations of the star (from Mt. Wilson) were made at a wavelength of 11.1 microns, which cuts through the tenuous gas and dust surrounding it. Quite an unusual red supergiant.
August 7th, 2009 at 7:23 am
It should be noted the top image, showing convection cells, is an artist impression, not a photo.
the third image on the bottom right is the actual image. I doubt the convection cells would be that large on such a large surface.