Cluster confusion

You may remember that I announced my intention to complete the open cluster program this year. Well we’re a couple of months in and a few things are clearer to me now. And that year’s seeming short than I’d expected.

When is a group of stars a cluster?

As a relatively new observer I’m used to open clusters like M37 which, courtesy of Stellarium, looks something like this.

Open Cluster M37 in Stellarium

They’re pretty obviously a cluster of stars aren’t they, so no problem there, even I can find that as long as I’m looking at the right one.

Unfortunately they’re not all like that. I was looking for NGC1662 last night in Orion, and it turns out to look like this.

Open Cluster NGC1662 in Stellarium

Now I found it, and it looked very much like that, but it wasn’t what I’d expected. I’ve been trying not to cheat by looking up the clusters ahead of time in case that distorts my observation. But you do need to know what you’re looking for.

This gives me a headache: when do a few nearby stars actually become a cluster?

In order to complete the program, I not only need to draw some of these clusters, but I need to classify all of them. To do that I’m going to need to answer my own question. Practice anyone?

Leave a Reply

Your email address will not be published. Required fields are marked *