Ann wrote:The delicate bow shock of LL Ori is a fascinating object, but there is another bow shock(?) in the picture. That is the rather bright bluish object at lower left, LP Ori or HD 36982. LP Ori is star of spectral class B1.5V, according to Simbad Astronomical Database. Is anything known about the bright nebula surrounding LP Ori?
It certainly does have an appearance of a curtain draped over LP Ori. I don't suppose it will get called a bow shock because it does not have quite the right shape ... at this time. But if that star is indeed embedded in the cloud there, it would make sense that it is responsible for that shape.
Strike that: I don't think I was looking at it right! Although to me, the overall shape looks like it is "draped over" LP Ori (from our perspective and the image orientation), if I look at it more carefully, I believe the arc to its upper left very well could be forming the same bow shape and even about the same orientation as the shock visible for LL Ori. So I think you are right. The coloring looks bluish, as you said, which makes me guess it is a reflection area. You probably know more about LP Ori's size and strength of output(?)
Thanks, Mark! Yes, I thought there are similarities between the obvious bow shock of LL Ori and the "draped blanket" over LP Ori. In both cases, the energetic outflow from the Trapezium could influence their respective shapes. The source of energy that is sculpting them seems to come from more or less the same direction.
As for LP Ori, it is a faint object, faint eighth magnitude. (LL Ori is obviously fainter, faint eleventh magnitude.) As I said before, the spectral class of LP Ori is B1.5V, or rather B1.5Vp, where "p" means "peculiar". The parallax of LP Ori was measured by the European satellite Tycho, which did a lousy job (or rather, it was unable to measure distances to objects as far away as LP Ori), so according to Tycho, LP Ori is a foreground object whose true visual luminosity is pretty much exactly one solar. Well, forget it. Obviously LP Ori is embedded in the Orion Nebula. Its apparent B-V index is about +0.1, which seems very reasonable, since LP Ori is definitely reddened by dust.
I believe that LP Ori is really quite young and therefore faint for its spectral class. I have noticed that other very young stars of spectral class B are fainter than their spectral class would suggest. The reason, I believe, is that stars are comparatively faint at the stage where they have recently got their hydrogen fusion going. I checked out a star just outside the Orion Nebula, HD 37303. This star, whose spectral class is B1V, is definitely likely to be older than LP Ori, but still young. HD 37303 is mostly unreddened and very blue, -0.20. The parallax of HD 37303 is 2.45 ± 0.48 milliarcseconds, suggesting a distance of around 1300 light-years. Its luminosity, as calculated from its parallax and apparent luminosity of 6.02, is more than 500 times solar. So what can we say about the likely luminosity of LP Ori? A hundred times solar?
Perhaps you, Mark, or some other math whiz could calculate the luminosity of LP Ori by assuming that its distance is about 1300 light-years and its apparent (and reddened) magnitude is about 8.4.
Personally I'm fascinated by the very dark cloud immediately to the left of LP Ori. My guess is that this dark cloud is either (and most likely) a remnant of the local cloud that gave birth to LP Ori, or else the outflows of the young object LP Ori has helped shape it or even make it. Well, that is not so likely.