The best infrared image yet of a star’s surface


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The surface of a star

Astronomers, using the Very Large Telescope in Chile have taken the best infrared image of the surface of a star, revealing gigantic granules or convection cells, across the star’s surface. These cells are somewhat similar to the bubbles you see when you simmer tomato sauce. Our own Sun usually has about two million such cells across its surface. For this aging red giant, which has the same mass as the Sun but has expanded to 350 times its diameter, things are different.

[The astronomers] found that the surface of this red giant has just a few convective cells, or granules, that are each about 120 million kilometres across — about a quarter of the star’s diameter [2]. Just one of these granules would extend from the Sun to beyond Venus.

I have posted the image on the right, reduced slightly in resolution to show here. The press release says that this is the first time that such granules have been imaged, but I think that is a bit of an overstatement. In fact, one of the very first articles I ever wrote, back in 1994, described an infrared image taken of Betelgeuse that showed similar giant bubbles or cells. What makes this image significant is its improved resolution. The ability to see smaller details on the faces of distant stars continues to improve.

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