Delta Geminorum has one claim to fame. It was just half a degree from Pluto when the little world was discovered, in 1930. Pluto has moved a third of the way around the sky since then. But Delta Gem has stayed put. It’s the seventh-brightest star in Gemini. It connects the body and legs of one of the twins.
The star is also known as Wasat. The name comes from Arabic, and means “middle.” But no one knows what middle is represented.
Delta Gem is a system of at least three stars. Two of them form a tight pair. But the third is far away – more than a hundred times the distance from Earth to the Sun. At that rate, the star takes about 1200 years to orbit the other two.
The system’s main star is a subgiant. That means it’s burned through most of the hydrogen in its core. It’s making the transition to the next phase of life: a giant. It’s already bigger than the Sun, but it’ll get even bigger over the next few million years. It’ll shine hundreds of times brighter than it does now, making it Gemini’s brightest star.
And it’ll get brighter for another reason as well. Today, it’s about 60 light-years away. A million years from now, though, it should pass within about seven light-years of Earth – making it one of the brightest stars in all the night sky.
Delta Gem is low in the east-northeast at nightfall, to the right of Gemini’s current leading light, Pollux. They soar high overhead later on, and remain in view all night.
Script by Damond Benningfield