このエピソードについて
It might seem hard to lose a star cluster. But that’s what happened with Messier 48. It was cataloged by French astronomer Charles Messier in 1771. When other astronomers looked for it, though, they couldn’t find it. In the early 1780s, Johann Bode and Caroline Herschel did see a cluster five degrees from the position that Messier reported. So they sometimes get credit for the discovery.
What all of these folks actually discovered was the nature of the cluster. Under especially dark skies, it’s visible to the eye alone as a faint smudge of light, so people had always known it was there. But the telescope showed that the smudge consisted of many individual stars.
Today, we know that M48 contains hundreds of stars. They’re packed into a loose ball that spans about 125 light-years. Most of the stars congregate near the center of that ball, which is the part that’s visible to the eye alone. The stars near the edge of the cluster are being pulled away by the gravity of the rest of the galaxy. Someday, those stars will leave the cluster and head off on their own.
M48 is 2500 light-years away. That makes it one of the most distant clusters of its type that’s visible to the eye. As night falls, it’s high in the southern sky. It’s well to the upper left of Sirius, the brightest star in the night sky. Binoculars reveal some of the individual stars of M48 – a cluster that got lost.
Script by Damond Benningfield
