Astronomy Blog

Altair

Via Fraser Cain at Universe Today, I've been reading a US National Science Foundation (NSF) press release about imaging the surface of a star. The star in question is Altair which is part of the Summer Triangle. Altair is a bit shy of twice the mass of our Sun, is about 10 times as luminous and rotates about three times per Earth day rather than our Sun's leisurely 25-30 day rotation rate. This rapid rotation means that the star is pretty oblate.

The right-hand image shows the actual observation whereas the left-hand image shows an artist's impression of it complete with fuzzy atmosphere. For me the right hand image - with it's lines of latitude and longitude - really shows that Altair is a flattened ball rather than egg-shaped. I have included both here to show the real data along with the pretty picture that is likely to be used by the news media. With these things, I always worry that newspapers will include the artist's impression with a caption implying that it is a photograph. Mind you, even Georgia State University can't get that right so I won't hold out much hope for the press.

The observations were made at infra-red wavelengths using an interferometric system on top of Mt Wilson in California. This technique connects the output of several telescopes and allows astronomers to simulate the effect of having a telescope as large as the distance between the telescopes. This only helps in resolution (the sharpness of the image) and doesn't help with sensitivity (the gray scales), but for a bright star like Altair it does the job. Radio astronomers have been using this technique for years to simulate radio telescopes the size of the planet Earth, so it is good to see it being used for other wavelengths.

There is a site with supporting material which links to more images and the Science paper.