Back in 2017, my wife and I went out to the desert to take a picture of a small open cluster known as Messier 37. The picture came out nice, it shows the bright cluster, full of blue, white, and yellow stars, in front of a very dark background. One thing we did not know, though, was that this cluster hides the oldest planetary nebula ever found in the universe!
Located between the constellations of Gemini and Perseus, at a distance of 4,500 light-years, M37 has an angular size of 24 arc-minutes and a true diameter of roughly 25 light-years. Although not visible to the naked eye, M37’s brightest stars are easily discernible through binoculars when viewed from a dark location. With a small telescope, you can observe about 20 bright stars, whereas larger instruments can unveil hundreds of stars, including the dimmer ones.
With an estimated age of 70,000 to 80,000 years, this planetary nebula is thought to be the oldest discovered in the universe. As of 2023, only the third planetary nebula was identified in an open cluster. Scientists have calculated that the gas within the nebula is expanding at 20 kilometers per second (12 miles per second).
The first attempt in 2017
In short, it is a picture of a small nebula hidden within a star cluster. It has been rarely photographed and was only discovered a few months ago. It also happens to be the oldest planetary nebula ever found and only the 3rd planetary nebula discovered within an open cluster of stars. There are several news articles about its discovery, as it is a pretty big deal, but none about an amateur astrophotographer having captured it. Here is a picture from the research team who discovered it (Fragkou et al., 2022):
As you can see (or not see, rather) in the picture, there is nothing there!
Our next attempt in 2023
Fast forward to 2023, and we decided to revisit this target, but this time with better equipment, a darker sky (very far away from light pollution), and, most importantly, better processing skills. We actually did not even know about the hidden nebula at first, and only found out by surprise when combining the data.
We connected remotely to our 655mm refractor telescope hosted at a remote observatory in Utah, and slewed to the cluster. We cooled the camera to -20C to reduce noise as much as possible, prepared our 4 filters (R, G, B, and HA) and launched the imaging sequence on the mini-PC that is attached to the telescope. We spent a total of 13 hours gathering photons on this object. 3 hours were spent on the R, G, and B filters, and 10 hours were spent with the Hydrogen Alpha filter. All the files were then calibrated and combined, ready to be processed.
The equipment used was as follows:
- Telescope: SVX130
- Camera: QHY600M
- Mount: GM1000HPS
- Filters: RGB (3 hours) + HA (10 hours)
The nebula in the cluster is mostly made up of Hydrogen Alpha, along with some Oxygen III in it as well. 10 hours of HA was just enough to reveal its beauty during processing. In order to bring out the faint nebulosity, I removed all the stars and used several tools to enhance the color, brightness, and details of the nebula. I then added all the stars back onto the image, and so both the stars and the nebula looked impressive.
Here is the full image, uncropped:
And now with a close up view on the nebula:
The nebula does not have any name, but just a destination: IPHASX J055226.2+323724.
Overall, the nebula is small and faint, but beautiful. It has a nice shape and beautiful red colors. The fact that it is behind bright colorful stars also makes it unique. Space never ceases to amaze!
About the Author
We are Antoine and Dalia Grelin. For the last ten years, we’ve been honing our skills as amateur astrophotographers. Our goal is to motivate people to jump into this wonderful hobby of astrophotography and help others to capture their first images of the night sky.
We do this through videos on our Galactic Hunter YouTube channel, hundreds of written tutorials on our astrophotography website, and through books about astrophotography. Half of our images are taken from the desert, far away from all the light pollution of the city, and the other half from our backyard in Las Vegas, NV using specialized filters