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Solar Twins

June 1, 2013

Most of the stars that dot the night sky are quite different from our own star, the Sun. An example is Antares, the heart of Scorpius, which is low in the southeast at nightfall. The bright orange star is a supergiant — it’s much larger and heavier than the Sun, and thousands of times brighter.

Under dark skies, though, you can just make out another star in Scorpius that’s a near twin to the Sun: 18 Scorpii, well to the upper left of Antares. It’s just a few degrees hotter than the Sun and a few percent brighter and more massive.

18 Scorpii is one of about a dozen “solar twins” identified so far. Studying these stars can help us understand more about the Sun itself — particularly since these stars are different ages from the Sun. Seeing them at different points in their evolution can help explain how the Sun changes over time.

One thing astronomers are particularly interested in is the magnetic fields of these stars.

The Sun’s magnetic field goes through an 11-year cycle. At the cycle’s peak, the Sun produces more magnetic storms, which can interfere with modern technology. At the same time, the Sun’s total energy output goes up by about one-tenth of one percent.

18 Scorpii’s magnetic field varies by about the same amount. But its cycle lasts just seven years. That may be because the star is close to a billion years younger than the Sun. So 18 Scorpii may be showing us what our own star was like in the distant past.

We’ll talk about another solar twin tomorrow.


Script by Damond Benningfield, Copyright 2013

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