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Supergiant stars are generally like electoral maps of the states — either red or blue. But third parties pop up every now and then, changing the color landscape.
An example is a star known as Sadr. It connects the body and wings of Cygnus, the swan, which is high in the east as night falls. Sadr is close to the upper right of Deneb, a blue supergiant that’s the constellation’s brightest star.
Sadr’s surface temperature is about the same as the Sun’s — roughly 10,000 degrees Fahrenheit. At that temperature, the star shines yellow-white. But that’s about the only thing that Sadr and the Sun have in common. Sadr may be more than 200 times the Sun’s diameter. At that size, if it took the Sun’s place it would extend all the way out to Earth’s orbit.
More important to the star’s lifecycle, though, it’s probably about a dozen times the mass of the Sun.
It might seem that a heavy star would last a lot longer than the Sun, but that’s not the case. Gravity squeezes the core of such a star much more tightly than a star like the Sun. That makes the core tens of millions of degrees hotter, which revs up the nuclear reactions in the star’s core. So while Sadr is only about three percent of the Sun’s age, it’s already nearing the end of its life.
And when the end comes, it’ll be spectacular. The star probably will explode as a supernova — the same fate that awaits all supergiants — red, blue, or something in between.
Tomorrow: sparks from a comet.
Script by Damond Benningfield