Betelgeuse: Ready to go Supernova?
2010-06-13 0:00

From: newscientist.com


The red supergiant Betelgeuse would extend to Jupiter if it were put in the sun's place in the solar system. A new study suggests it has shrunk by more than 15 per cent since 1993 (Image: A. Dupree/CFA/R. Gilliland/STScI/NASA/ESA)


Pinned prominently on Orion's shoulder, the bright red star Betelgeuse hardly seems like a wallflower. But a new study suggests the giant star has been shrinking for more than a decade.

Betelgeuse is nearing the end of its life as a red supergiant. The bright, bloated star is 15 to 20 times more massive than the sun. If it were placed at the centre of the solar system, the star would extend out to the orbit of Jupiter.

But the star's reach seems to be waning. New observations indicate the giant star has shrunk by more than 15 per cent since 1993. This could be a sign of a long-term oscillation in its size or the star's first death knells. Or it may just be an artefact of the star's bumpy surface, which may appear to change in size as the star rotates.

Betelgeuse is enshrouded by vast clouds of gas and dust, so measuring its size is difficult. To cut through this cocoon, Charles Townes of the University of California, Berkeley, and colleagues used a set of telescopes that are sensitive to a particular wavelength of the star's infrared light.

The team used these instruments to measure the size of Betelgeuse's disc on the sky. Over a span of 15 years, the star's diameter seems to have declined from 11.2 to 9.6 AU (1 AU, or astronomical unit, is the distance from the Earth to the sun).

Ejected Gas

The cause for this reduction is unknown, as it is unclear how red supergiants behave near the end of their lives.

"Maybe there's some instability in the star and it's going to collapse or at least go way down in size or blow off some material, but who knows," Townes, who shared a 1964 Nobel Prize for the invention of the laser, told reporters on Tuesday at a meeting of the American Astronomical Society in Pasadena, California.

The shrinking size could also be evidence of an as-yet-unidentified pulsation in the star, says Graham Harper of the University of Colorado in Boulder, who was not affiliated with the study.

The surface of Betelgeuse is known to wobble in and out, fed in part by the roiling energy of convection beneath its surface. Two such pulsations are already known – one seems to start anew each year, the other every 6 years. Since this observation shows a progressive decrease in the size of the star over 15 years with a consistent set of measurements, Harper says: "I think this is a very nice indication that [Betelgeuse] is getting smaller."

Bumpy surface

But he notes the change in size could be an illusion. Simulations suggest temperature differences in red supergiants can make their surfaces extraordinarily bumpy, causing the star to appear to be a different size when viewed from different angles.

"Often if you look at the simulations, the star is not spherical. It looks like a bad potato," Harper told New Scientist. Betelgeuse is thought to rotate every 18 years or so, which might suggest an especially narrow part of the star recently rotated into view.

Another possibility, Harper says, is that the team is not measuring the surface of the star but a layer of dense molecular gas that some astronomers suspect may hover above it.

The team hopes to get higher-resolution pictures of the star at a variety of wavelengths to determine the origin of the light they are seeing.

Source: newscientist.com



Related Articles
Seeing Red: Will Betelgeuse Go Supernova in 2012? (pdf)


Latest News from our Front Page

Swedish parliament removes Baroque artist's bare breasted painting for offending feminists and Muslims
2015-03-06 3:28
A nude painting named Juno, which was painted by baroque artist G E Schröder and has hung in the dining room of the Swedish Parliament for 30 years has been taken down for fear of offending the sensitivities of feminists and Muslim visitors, Swedish newspaper, The Local reported on Thursday. Explaining the ban on the baroque breasts, a source from the ...
White US children will be minorities by 2020 after immigrant 'baby boom', Census reveals
2015-03-05 19:50
This is the result of an ongoing trend of declining birth among white Americans and a baby boom among immigrant groups, as well as a surge in immigration. By the year 2020, 50.2percent of all children in the US are expected to be non-white, according to the Census. By 2044, whites will be outnumbered by minorities. The Census study, released ...
New Jersey Shopkeeper Hangs 'White History Month' Sign In Window
2015-03-05 18:08
A deli owner in Flemington, New Jersey, has angered many of his neighbors by posting a sign on his window that reads, "Celebrate Your White Heritage in March White History Month." Jim Boggess, who is the owner of Jimbo's Deli, says he put up the sign to remind everyone that they should be proud of their race and culture. "No matter what ...
The Viking ”Maine Penny” Mystery
2015-03-05 3:41
In 1957, during his second year of digging at the Goddard site; a large prehistoric Indian trade village in Penobscot Bay on the central Maine coast, local resident and amateur archaeologist Guy Mellgren found a small silver coin. The coin is later identified by experts as a Norse silver penny dating to the reign of Olaf Kyrre, king of Norway ...
The Sagas of the (Viking) Icelanders Shed Light on Golden Age
2015-03-05 3:40
The Sagas of the Icelanders have long been preserved as the most comprehensive specimen of the literary culture of the 13th and 14th centuries of Iceland. In writing these sagas, many attributes of the 10th and 11th centuries were conserved, particularly individual biographies, the history of family feuds, and the overall evolution of the one of the greatest settlements ...
More News »