Astro-Shed

Messier 78 is a reflection nebula in the Orion constellation discovered by Pierre Mechain in 1780. It is about 1350 light years distant and approximately 5 light years in diameter.

Unlike emission nebula which shine by the ionization from nearby hot highly energetic stars, reflection nebulae shine by reflecting or scattering light from cooler stars. The effect is very similar to that of our own sun whose light is scattered in our atmosphere to make the atmosphere appear blue in color. The color of the reflected scattered light is associated with the size of the molecules or particles in the cloud and called the Rayleigh Scattering Effect.

If you look carefully there is a dense dark cloud of dust that begins in the top left corner and winds down around and then through the reflection nebula to finally widen and exit out the bottom right of the frame. The ESO Euclid Space Telescope’s infrared images revealed hundreds of thousands of stars concealed by this dark nebula. You can get a glimpse of a few of them as they peek through the nebula’s dark curtain, appearing golden yellow in color surrounded by blackness towards the bottom of the image.

I find M78 a difficult visual object and visible only under darker skies, however, it is an easy object to image. This image was taken with a luminance filter which blocks infrared and ultraviolet light which the camera is sensitive to and can cause the stars to “bloom.” The image is 4.5 hours of 3-minute subs with a ZWO ASI MC Pro color camera through an Astrotech AT80ED scope driven by a ZWO AM5n mount.