Right next to the California nebula both in my post feed and in reality is the Pleiades star cluster, aka Messier 45. At “only” about 444 light years away, it’s the closest Messier object to earth, and the brightest naked-eye star cluster in the sky.
M45 was known to ancient cultures around the world, having been featured in ancient works such as the Bible and the Nebra sky disk, and has been used to indicate important dates for ancient cultures. What the ancients DIDN’T know is that the cluster contains more than 1,000 stars, most of which are hot, young B-type stars, and is only about 100 million years old. For a long time, the bright reflection nebulae surrounding the Pleiades was thought to be leftovers from the cluster’s formation, but more modern research has revealed that that’s not the case. The stars are instead simply passing through a dusty region of the interstellar medium, which the whole area around the Pleiades, Hyades cluster and California nebula is full of.
The cluster is currently taking its sweet time moving towards the southern portion of Orion, and will disperse within the next 250 million years.