Bright Triangle

With a little imagination, you can find geometric figures just about anywhere in the night sky. An example is a right triangle of stars in Perseus and Andromeda. The constellations are high in the east and northeast as darkness falls.

At the top of the triangle is Almach, Andromeda’s third-brightest star. Through a small telescope, it looks like two stars — one of the most beautiful double stars in the night sky. One of them is yellow-orange, while the other is blue.

The blue star is a system of three stars on its own. Two of them orbit each other, while the pair of them share an orbit with star number three.

The second point of the triangle is directly below Almach in early evening. And it, too, is complicated.

Algol consists of three stars. Two of them line up in such a way that they eclipse each other. The fainter star passes in front of the brighter one every three days or so. When that happens, Algol fades to about a third of its normal brightness. Early skywatchers found that a bit spooky, so they gave the star a spooky name: Algol means “the demon.”

The third and brightest member of the triangle is Mirfak, to the left of Algol. As far as anyone knows, it’s a single star. But it’s an impressive one. It’s about eight times the mass of the Sun, and thousands of times the Sun’s brightness. So it’s an easy target, even though it’s farther than the other members of the triangle — about 500 light-years from Earth.

Script by Damond Benningfield