Messier 42 - The Great Orion Nebula
Date: Dec 23, 2019
Revised Feb 12, 2025, and Sept 16, 2025
Cosgrove’s Cosmos Catalog ➤#0016
Awarded Flickr “Explore” Status!
Messier 42 - The Great Orion Nebula (click to enlarge)
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The Orion Nebula - One of the Most Beautiful Objects in the Sky
About the Target
Messier 42—The Orion Nebula, or the Great Orion Nebula, is one of the brightest and most beautiful nebulae in the night sky! Also known as NGC 1976, this diffuse nebula is located 13,44 light-years away in the constellation of Orion.
Spanning roughly 25 light-years across, the Orion Nebula has about 2,000–3,000 times the mass of our Sun in gas and dust. This area is a stellar nursery, and new stars are continually being born there. While the Milky Way Galaxy has many star formation regions, M42 is one of the closest to Earth.
At magnitude 4.0, M42 is one of the brightest nebulae in the sky and can be seen with the naked eye. It is also surprisingly large. Its apparent size in the sky is around 1 degree (about two full Moons across) at its full extent.
The Orion Nebula is best observed on winter nights (peaking in January around 10 PM) when the constellation Orion stands high in the sky.
It can be seen as a fuzzy region around the middle star, the sword that hangs from Orion’s Belt. Binoculars show even more nebulosity, and even small telescopes show the nebula with a dark void often described as the “Fish's Mouth” and a bright star cluster at its core, known as the Trapezium.
The Trapezium is a young open cluster of what appears to be four stars located in a bubble about 1.5 light-years in diameter. Though it appears as four main stars in small telescopes, the Trapezium actually contains multiple young, massive stars (at least six are readily identifiable in good conditions. These stars blast intense ultraviolet light that carves out a cavity in the nebula, illuminating the surrounding gas. Some of these stars can be resolved as double stars. This bright group of new stars illuminated the gas and dust in the area. It may be a sub-component of the larger Orion Nebula Cluster, a grouping of about 2,000 stars within a diameter of 20 light-years.
The Orion Nebula is among the most scrutinized celestial objects, providing key insights into how stars and planets form. Astronomers have observed protoplanetary disks and even brown dwarfs inside M42, meaning this nebula has taught us not just about the formation of new stars, but also about the birth of new solar systems!
M42 is surrounded by a much larger cloud hundreds of light-years wide. Nearby famous objects – like the Horsehead Nebula and Barnard’s Loop – are all connected in this enormous star-forming complex.
M42 has a smaller companion nebula, Messier 43, divided by the dark dust lane known as the “Fish’s Mouth. That dark void, nicknamed the Fish’s Mouth, actually separates M42 from a smaller neighboring nebula, M43 (De Mairan’s Nebula).
History
The Orion Nebula has fascinated observers for centuries. The first recorded observation of its nebulous nature was by French astronomer Nicolas-Claude de Peiresc in 1610. Later, Christiaan Huygens sketched its bright core (sometimes called the Huygens Region) in 1656, and Charles Messier cataloged it as M42 in 1769.”
Interestingly, M42 was the first nebula ever photographed – Henry Draper managed to image it in 1880 with an 11-inch telescope and a 50-minute exposure. This early astrophoto (in black-and-white) barely hinted at the nebula’s glory, but it was a landmark in astrophotography. He kept at it and a year and a hlf later took an improved image with an exposure of time of 137 minutes.
Henry Draper (1837-1882) (click to enlarge)
The very first photograph of the Orion Nebula, taken September 30, 1880. (Henry Draper) (click to enlarge)
Photograph of the Orion Nebula, March 14, 1882. A great shot of the “Fish’s Mouth.” (Henry Draper) (click to enlarge).
Everybody who does astrophotography shoots this very famous object at some point or another. This is my very first shot at it.
The Annotated Image
An annotated image of the Orion Nebula was created by using Pixinsight’s ImageSolver and AnnotateImage Scripts. This annotation labels major stars and features, including the Trapezium stars and the smaller M43 nebula.
The Location in the Sky
IAU/Sky & Telescope Constellation Map of Orion - with M42 region marked by the yellow arrow.
About the Project
M42 is a very high-dynamic-range scene, and it is very easy to saturate the brightest parts.
So, my strategy for this project was to use one series of longer exposure subs to pull in the nebula, another series of short exposure subs with short to capture the bright areas, and then blend them.
So I did 20 x 3-minute exposures of the main nebula and 20 x 2-second exposures of the Trapezium and brighter portions.
Processing was originally all done in Photoshop, and the two images were blended using a mask.
I was pretty happy with the original image I produced with this effort. It was evident that there was a lot of detail and structure. In fact, it was the very first image I made that I felt confident enough about to share with the local Astronomy Group.
I got a pretty good response when I shared the image.
However, my initial image seemed to have a lot of green tones. In general, there is not much green coloration in deep-sky objects unless they are some kind of planetary nebula. But at the time, I did not know this. Below is my original image.
My original processing of M42. (Click to Zoom)
After I started using Pixinsight for image processing, I returned to my M42 data and completely reprocessed it, using the Photometric Color Calibration routine to set the color. The final result of that effort is the image that I used as the main one for this posting. I was very happy with this version of the image!
It was not until much later that I learned that M42 has a subtle green color caused by a double ionization process that occurs only with rarefied gases. So, maybe my original is right.
Which do you like better?
More Information
🔭 Target Details:
NASA APOD – The Great Nebula in Orion (2024 Nov 4) – NASA’s Astronomy Picture of the Day featuring M42, noting it spans ~40 light-years and lies ~1500 light-years from Earth .
SIMBAD – M42 (Orion Nebula) – Astronomical database entry listing M42 as an H II region and giving its coordinates (05:35:16.8, –05:23:15, J2000).
Aladin Lite – Orion Nebula field – Interactive sky atlas view centered on the Orion Nebula, allowing zoom and multi-survey overlay exploration of the region.
Trapezium - Wikipedia entry for the Trapezium
Wikimedia Commons – Orion Nebula – Category page with hundreds of freely-licensed images of M42 (over 600 files as of now).
📜 History & Naming:
Wikipedia – Orion Nebula – Overview of M42’s names and discovery, noting that older texts call it the “Great Nebula in Orion”.
Encyclopedia Britannica – Orion Nebula – Summary of M42’s history, mentioning its discovery by Peiresc in 1610 and that it was the first nebula ever photographed (in 1880)
NASA (Hubble) – Messier 42 (Orion Nebula) – NASA article describing M42’s significance, including its mythic view as a “cosmic fire” by the Maya and its status as the nearest large star-forming region (~1500 ly away) visible to the naked eye.
🔬 Science & Observations:
Chandra (2000) – X-Ray Hot Stars in the Orion Nebula – Chandra X-ray results showing the Orion Nebula Cluster (~2000 young stars within ~10 light-years) and the compact Trapezium subgroup (~0.5 ly radius) of ∼300,000 yr age.
EarthSky – JuMBOs in the Orion Nebula (2023) – Article on James Webb Telescope findings: 540 free-floating planetary-mass objects found in M42 (at 1,344 ly), including puzzling binary “JuMBOs” (Jupiter-mass Binary Objects).
💡 Interesting Facts & Outreach:
Space.com – Orion Nebula: Facts about Earth’s nearest stellar nursery – Popular astronomy article noting that M42 (Messier 42) is the nearest star-forming region; fun facts include that it generates enough water to fill Earth’s oceans ~60 times per day.
APOD (2024 Sep 10) – Horsehead and Orion Nebulas – NASA’s APOD mosaic featuring the dark Horsehead Nebula alongside the glowing Orion Nebula, illustrating both famous nebulae in one wide field.
Chandra Observatory – Images of the Orion Nebula – Chandra photo album showing X-ray and optical views of M42; describes intense X-ray flaring by young stars in the cluster (ages ~1–10 Myr).
Capture Details
Light frames
30 x 180 seconds, bin 1x1 @ -15C, unity gain
20 X 2 seconds, bin 1x1, @-15C, unity gain
Total of 1.5 hours
Cal Frames
• 25 bias frames at 1 second, bin 1x1 @ -15C, unity gain
• 25 Darks 180 seconds, bin 1x1 @ -15C
• 25 Darks 2 seconds, bin 1x1 @ -15C
• 25 Flats
Capture Hardware
Scope: William Optics 132mm f/7 FLT APO Refractor
Focus Motor: Pegasus Astro Focus Cube 2 - new
Guide Scope: Apterna 60mm Guidescope - new
Mount: Ioptron CEM 60
Tripod: Ioptron Tri-Pier
Camera: ZWO ASI294MC-Pro
Guide Camera: ZWO ASI290MM-Mini
Dew Strips: Dew-Not Heater strips for Main and Guide Scopes - new
Power Dist: Pegasus Astro Pocket Powerbox - new
USB Dist: Startech 8 slot USB 3.0 Hub - new
Polar Alignment Camera: Polemaster
Software
Capture Software: PHD2 Guider, Sequence Generator Pro controller
Image Processing: Deepsky Stacker, Pixinsight, Photoshop - assisted by Coffee, extensive processing indecision and second-guessing, editor regret and much swearing….
