Herbig-Haro (HH) objects are small shock wave nebulae due to outflow activity from newborn stars. Their discovery dates back to landmark papers by Herbig (1950,1951) and Haro (1952, 1953).

This image captures 16 faint HH objects caused by 3 independent HH jets in the Orion area. The HH objects are reddish because they only show up on the Ha filter. Other HH objects are also visible in the image but they are not associated with the 3 jets of interest and are not labeled in the annotated image. Much of the information here is from the 2013 paper, "HH 222 : A Giant Herbig-Haro Flow from the Quadruple System V 380", by Reipurth, Bally, Aspin, Connelley, Geballe, Kraus, Appenzeller, and Burgasser. It is an interesting read.

The first jet, labeled in blue, includes the first two HH objects ever discovered, HH 1 and HH 2. HH 2 seems connected to a large circular swirl in my image. HH 1 and HH 2 are spaced one light year apart, symmetrically opposite a star (not visible in my image) which is ejecting material in both directions along its polar axis. This jet also created objects HH 3 and HH 401. HH 401 is a large, fascinating cone shaped object, and really looks like a shock wave moving outward from the source. HH 401 must be much older than the other objects based upon its distance from the source.

The second jet, labeled in yellow, is the HH 34 jet. Like the first jet, neither the jet or the source are visible in my image. The total length of this jet from HH 33 to HH 88 is estimated to be 10 light years. It is interesting to me that so many of these HH objects occur in pairs equidistant and in opposite directions from the source star, implying a similar bi-polar burst and resulting shock wave through space.

The third, and to me most interesting, jet originates from the V380 Orionis multiple variable star system and is labeled in white. This star system is obscured by the Keyhole Nebula (NGC1999), a bright blue reflection nebula located 1500 light years away. In the center of this nebula, from our visual perspective, is a dark area. This area has been described as a keyhole or a triangle, but I think it looks more like a capital "T". It was previously thought that this T was a dark nebula - a patch of dust and gas blocking the background light. But recent work within the past 10 years has determined that this T shape is simply empty space, cleared of dust and gas. The exact cause of this phenomenon is still being investigated.

The first HH object discovered relative to this third jet was HH 35, which lies very close to the source star. HH 130 was then discovered, and much later the dim, equidistant HH 1031 was discovered on the opposite side. This HH object is just a faint blur in my image. The most fascinating object in the whole image is HH 222, the Waterfall Nebula. This shock wave is an incredible 2 light years long. Since its discovery, the source of this object was not well understood. At the center of HH 222, two infrared sources were discovered and thought to be somehow responsible for creating the HH object. But recent work in the 2013 paper mentioned above showed that the two sources are distant elliptical galaxies and could not be the cause of the object, indicating that the infrared sources were just a line-of-sight coincidence. Instead, the researchers proved that HH 222 is, incredibly, caused by the distant V380 Orionis jet. Part of this proof is that HH 222 is aligned with the other HH objects along the jet path, plus the bow shock of HH 222 is moving directly away from the V380 source. Also, a newly discovered companion HH object (HH 1041) has been found in the opposite direction of HH 222 along the jet path, and is likely part of the counterflow. My field of view for this image was not wide enough to capture HH 1041. The total extent of this jet and HH complex is 17 light years long, one of the largest HH complexes known.