Look south just after sunset today and you’ll see the unmistakable constellation of Orion.

Follow Orion’s belt left and down and you find Sirius, the brightest star in the sky. Sirius is so bright for two reasons. First, it really is a bright star, shining some 25 times brighter than the sun. Second, Sirius is on our cosmic doorstep. At a mere 8 light years away it’s one our next door neighbours in space.

https://en.wikipedia.org/wiki/Sirius

Sirius is surrounded in our view of the sky by a bunch of light smudges. These are open clusters of stars. A closeup map from Stellarium shows a few of the brighter ones. Many of these are visible with binoculars.

And here are a few of the brightest ones: M46, M47 and M50.

I particularly like M46 because it includes a bright orange foreground star, 140 Pup, a red giant 700 light years away. This contrasts with the main cluster which is nearly 5,000 light years away.

https://en.wikipedia.org/wiki/Messier_46

Open star clusters tend to show mainly young, bluish stars. They’re usually regions of recent star formation where the constituents haven’t yet dispersed. We mostly see the brightest members which tend to be blue-white in colour. Their dimmer, yellow-red companions are outshone by these blue-white stars.

M46 has another surprise though. It also includes a planetary nebula, shown near the top left of this photo. It goes by the charming name of NGC 2438.

https://en.wikipedia.org/wiki/NGC_2438

Again, this is a foreground object about 1,300 light years away. It’s not a true member of the cluster. Planetary nebulae have nothing to do with planets. They just look a bit like planets. They’re the remnants of old stars that have blown off their outer atmosphere and are now illuminated by the remaining core at their center. Given that this is an older star, it should now be obvious that it can’t truly be part of the open cluster M46.

On the opposite side of the sky, I’m still stacking photos of M13, the Great Globular Cluster in Hercules. This is three night’s worth of photos stacked. I’m not sure if adding any more to this will improve the quality or not. Only one way to find out…

All photos taken with my Seestar S50.