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ALMA's image of red giant star gives a surprising glimpse of the sun's future
A team of astronomers led by Wouter Vlemmings, Chalmers University of Technology, have used the [Atacama Large Millimeter Array] to make the sharpest observations yet of a star with the same starting mass as the Sun. The new images show for the first time details on the surface of the red giant W Hydrae, 320 light years distant in the constellation of Hydra, the Water Snake. W Hydrae is an example of an AGB (asymptotic giant branch) star. Such stars are cool, bright, old and lose mass via stellar winds. The name derives from their position on the famous Hertzsprung-Russell diagram, which classifies stars according to their brightness and temperature.
[...] Alma's images provide the clearest view yet of the surface of a red giant with a similar mass to the Sun. Earlier sharp images have shown details on much more massive, red supergiant stars like Betelgeuse and Antares. The observations have also surprised the scientists. The presence of an unexpectedly compact and bright spot provides evidence that the star has surprisingly hot gas in a layer above the star's surface: a chromosphere. "Our measurements of the bright spot suggest there are powerful shock waves in the star's atmosphere that reach higher temperatures than are predicted by current theoretical models for AGB stars," says Theo Khouri, astronomer at Chalmers and member of the team. An alternative possibility is at least as surprising: that the star was undergoing a giant flare when the observations were made.
Other best-ever images of stars. W Hydrae is the 7th brightest star in the night sky.
The shock-heated atmosphere of an asymptotic giant branch star resolved by ALMA (DOI: 10.1038/s41550-017-0288-9) (DX)
Previously: Very Large Telescope Interferometer Captures Best Ever Image of Another Star (Antares)
(Score: 2, Interesting) by dierdorf on Monday November 13 2017, @09:55PM
Well,W Hyd is the 7th brightest star if you happen to have superpowers and can see in the Infrared. For us mere mortals it isn't visible at all, having visual magnitude which varies from about +6 to +10 or so. (It's a "Mira" variable, which pulsates. At its largest diameter, almost ALL its energy is emitted in the infrared. The brighter Mira stars just periodically "go out" to the naked eye, which is how the prototype Omicron Ceti was given the name "Mira", The Wonderful. It was the first star proven to be a variable; before that stars were assumed to be of fixed brightness.) BTW, the more or less second naked-eye variable star to be recorded was called Algol, i.e., al-Ghoul, the monster.