Yep, satellite. I once saw one go across the face of the moon while I was doing a sketch of it. I was able to make out its body and solar panels and various antennae. Very fast apparition, and it really surprised me, but WOW!
With that oblong patch you mention in M42, did it
resemble the patch seen in this sketch?
If so, then it is a feature in M42 that is call the "Fish Mouth". It is actually a 'dark pillar', a concentration of gas and dust that surrounds protostars - stars that are forming and are soon to kick off their nuclear fire. The Fish Mouth juts up infront of the brightest section of M42, so we see it silhouetted against the bright background. Those really bright stars right next to the fish mouth that form the "Trapesium" is the powerhouse of energy that is causing the nebula to glow. It is the solar wind those stars are emitting that is pushing the surrounding gas and dust away from those protostars, and the resulting pillar shape is the tell-tale sign of their existance as it is their gravity that is keeping the cocoon that envolopes them from being stripped away by that stellar wind.
The Fish Mouth is probably the easiest dark pillar to see. Others can be seen relatively easily in the Eta Carina nebula - an 8" scope will show upto four, thin, skeleton like fingers jutting up into the brightest part of the nebula.
The Eagle Nebula, also called the Pillars of Creation, is also a set of dark pillars, but these require a larger scope, probably 10" and over to see. I managed to see the Eagle in my 17.5" earlier this year for the first time. My sketch below is the view of it.
Another form of dark pillars is called 'Bok globuals', these are the same thing but without the long column, so they appear as small dark blobs. Some of these are visible in larger scopes, but as they are much smaller than the pillars, they are harder to see.
