Moon and Antares

StarDate: January 7, 2013

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The surface of a star looks like a pot of boiling water. Giant bubbles of hot gas rise from deep inside the star, carrying heat to the surface.

But there are bubbles, and then there are bubbles. On the Sun, for example, these bubbles — known as convection cells — are typically as big as Texas. On the biggest stars around, though, the cells can be hundreds of times bigger than the Sun.

These stars are known as red supergiants, and a prime example is in good view the next couple of mornings. Antares, the bright heart of Scorpius, is below the Moon at first light tomorrow, and to the right of the Moon on Wednesday.

Antares is one of the most impressive stars in the galaxy. It’s around 15 times the Sun’s mass, hundreds of times the Sun’s diameter, and when you combine all wavelengths of light, tens of thousands of times brighter.

Its core is much hotter than the Sun’s as well, so there’s a lot of heat that’s trying to escape. It does so in the form of giant convection cells.

Antares is so far away that it’s almost impossible to see these cells. But computer simulations show that they may come in a couple of sizes. The little ones are perhaps 50 times wider than the Sun, and last for a few months. The big ones are a couple of hundred times the Sun’s diameter. These giants last for years, and as they cool, they may plunge all the way to the star’s core — where they heat up and once again bubble back to the surface of this giant star.

Script by Damond Benningfield

For more skywatching tips, astronomy news, and much more, read StarDate magazine.

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