IC 4665 [1]
A star cluster that was “discovered” several times climbs the eastern sky this evening. IC 4665 is a quarter of the way up the sky as it gets good and dark. It’s to the lower right of the brightest star of Ophiuchus the serpent-bearer.
Under really dark skies, the cluster is just visible to the unaided eye. It looks like a hazy patch of light a bit bigger than the full Moon. So people had actually seen it since they first looked into the night sky.
What astronomers discovered was the nature of this hazy object: a cluster of stars.
It was first recorded by Philippe Loys de Chéseaux, around 1745. There were no scientific journals in which to publish discoveries, though. Instead, astronomers let others know about them at meetings of scientific societies, or in letters. Chéseaux didn’t do that, though, so his discovery wasn’t known until much later.
By then, the cluster had been discovered twice more. Johann Bode found it in 1782, but he didn’t share the discovery, either. And the next year, it was discovered by Caroline Herschel. But she didn’t record it in her catalog of star clusters, so it still wasn’t publicized.
In fact, it wasn’t listed in any catalog until the early 1900s, when it was recorded by Harvard College Observatory.
Today, we know that IC 4665 contains a hundred or so stars. It’s at least 1200 light-years away. And it’s no more than 40 million years old — a young family of stars that kept getting discovered.
