Moon and Spica

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Moon and Spica

The heart of the Sun is a toasty 27 million degrees Fahrenheit. At that temperature, atoms of hydrogen ram into each other and stick together to make helium. And they’ll continue to do so for another five billion years.

The cores of some stars are much hotter than the Sun’s, so the nuclear reactions happen at a much faster rate.

The key difference in stars is their mass. A heavier star has a more powerful gravitational pull. That squeezes its core more tightly. And the tighter the squeeze, the higher the temperature.

An example is Spica, the brightest star of Virgo. It rises well below the Moon in the wee hours of tomorrow, but will be closer to the Moon the following couple of days.

Spica consists of two giant stars. The heavier one — Spica A — is 11 or 12 times the mass of the Sun. With all those extra pounds, its core is tens of millions of degrees hotter than the Sun’s. As a result, its fusion reactions take place far more quickly. So Spica A will use up its hydrogen in about 30 million years.

After that, the core will shrink and get even hotter. That will trigger reactions with heavier elements. The star will step through that process several times, until its core consists of iron. At that point, despite a temperature of more than a billion degrees, the reactions will stop. Spica’s core will collapse. Its outer layers will fall in, then rebound, creating a titanic explosion — bringing Spica A to a spectacular end.

Script by Damond Benningfield

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