Astronomers view a star in close-up

Astronomers have zoomed in to observe detail on the surface of a star like the Sun for the first time. They used a special technique that counters distortion caused by the Earth’s atmosphere to focus on nearby Altair.

Their data was taken by an artist and used to produce an image showing a star with bright patches on its surface and a bulge caused by its rapid spin – around 60 times faster than the Sun’s.

Scientists from the University of Michigan made the breakthrough by observing Altair simultaneously with four telescopes on Mount Wilson in California. By detecting the differences between the images observed, the scientists were able to compensate for the effects of our atmosphere.

It is not the first time that we have managed to record detail on a star. However, previous targets have been red giants including, famously, Betelgeuse in Orion which was mapped with the UK’s William Herschel Telescope on La Palma in 1989. Planets are now also being mapped.

Altair is much smaller than the red giants – it is a star that is nearly twice as big as the Sun, hotter and younger and which lies nearly 17 light-years away. It is also one of the brightest stars in the sky, clearly visible in the constellation of Aquila, the Eagle.

The telescopes used to study Altair form part of the Center for High Angular Resolution Astronomy (CHARA) operated by Georgia State University on Mount Wilson.

John Monnier, lead author of a paper published in Science, said: “This powerful new tool allows us to zoom in on a star that’s a million times farther away than the sun. We’re testing the theories of how stars work in much more detail than ever before.”

It might not be long before we are able to detect sunspots on other stars, using a British tool called SuperWASP that has been set up to detect extrasolar planets.

Peter Wheatley, a member of the team, from Warwick University, told me last year how this bank of cameras will record the dimming in a star’s light when a planet passes in transit across its disk. Peter said that if the planet passed in front of a darker sunspot, the light of the star would brighten once more, revealing its presence. Other planet spotters such as the Corot satellite will be able to show similar detail.

The artist’s rendition of Altair is by Zina Deretsky, National Science Foundation.

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