Alrighty. I've done some more research AND observing of proplyds in M42. But it seems I still have a long ways to go. So please bear with me as I continue to learn.

I've now observed THREE objects in which I believe the light I see is purely that of an ionized protoplantary disk. From easiest to hardest at 600x in my 16-inch, they were: proplyd 244-440 (nonstellar), proplyd 170-334 (stellar), and proplyd 143-425 (stellar).

The brightest object I have seen and the subject of my OotW is proplyd 159-350. I am currently of the opinion that the light I'm seeing is a roughly 50-50 mix of the ionized disk and the young stellar object (YSO) visible seemingly behind it. So please note this fact in your logs if you observe it.

In the image below, I've gone ahead and labeled three YSOs. These are objects that have proplyds associated with them but that are too faint to be visible. To read more about the three, check out Walter van Rossem's 2014 thesis on them. Proplyd 218-354 is the most famous of the three because it consists of a YSO surrounded by a pure silhouette disk, which means its protoplanetary disk is seen in silhouette against the bright background nebula. Apparently, the distance to Theta1 Ori C and Theta2 Ori A is large enough that the radiation from either star is not intense enough to start a neutral, photo-evaporative flow. I can tell you firsthand it's easier to see than proplyd 159-350!

OotW.jpeg
North is up and East is left. Image Credit: Franz Hofmann & Wolfgang Paech

Final thoughts. From observing and from studying a bunch of images, I still am struggling to believe that Victor is seeing proplyd 155-338 while not seeing proplyd/YSO 159-350. Also, for the first time ever, I found the "E" star in the Trapezium to be reddish-brown at 440x in my 16-inch on the evening of 2/17. That was so amazing that it would've been the highlight of my night...if it wasn't for me seeing the (apparently) largest known proplyd in the Orion Nebula, 244-440, as nonstellar at 440x!! It's disk is about 5" across, which corresponds to over 2,000 AU across. Incredible. I'm just starting to research it, but it might be the brightest "pure" proplyd visible...

Scott H.