The “Castaway Cluster”
Today, a small open star cluster visible from most parts of the world that will take your breath away. Set in the most star-rich section of the Milky Way and surrounded by dark nebulae that look like holes in space itself, the “Castaway Cluster” is too beautiful to miss.
The Basics
• The Castaway Cluster, catalogued as NGC 6520, is located just above the spout in the “Teapot” of Sagittarius. This is a rich region of the Milky Way containing many gas clouds and star clusters, including the Lagoon and Trifid Nebulae. NGC 6520, a tiny jewel of a cluster, is often forgotten amongst these more famous sites.
• NGC 6520 is easy to find… just 3 degrees or so north of Alnasl, the star at the tip of the spout in the Teapot. Just west of the cluster, in good sky, you can also see the conspicuous dark nebula Barnard 86.
Red circle marks the location of NGC 6520, above the “spout” of Sagittarius
A Deeper Look
• This open cluster is only 800 million years old and contains many hot blue stars. Within the field of view, you will also see bright red stars that are likely not associated with the cluster but simply share the same line of sight.
• The Castaway Cluster is some 5,300 light years from Earth. It’s 60 or so stars span 8 light years. On a good night, you’ll see perhaps 15-30 of these stars.
• NGC 6520 is also a distant cluster. That means it appears quite tiny in our skies. While you can see it in binoculars, you’ll need a telescope with at least 150-200x to resolve this tight family of fairly new stars. The dark splotch of Barnard 86 is located between the cluster and the bright star to the west. Try averted vision… you may see more dark nebulae.
Star cluster NGC 6520, with the dark nebula Barnard 86.
Good To Know
The Castaway Cluster was so named by Stephen J. O’Meara because it looks like a tiny island in a tempestuous sea of stars. It reminded him of the story of the castaway Robinson Crusoe, shipwrecked on a small island near the coast of Venezuela in 1659.
Personal View
NGC 6520, at best, is always low in the sky from my part of the world. But I never tire of looking at it. No doubt it’s even better from southern skies. With the star cluster and nearby dark nebula, it’s also a striking region to photograph through a telescope if you have the means.
