Object of the Week, February 28, 2022 – HH 222, the Waterfall

[Howard B]

Orion
Herbig-Haro object
RA: 05 35 37
Dec: -06 23 43

HH Objects in the Orion Complex.jpg

I’ve used this photo before, but this KPNO image shows an amazing number of HH objects north of NGC 1999, as well as HH 1/2 just south of it. What a beautiful part of the sky! Perhaps the most intriguing object here is the graceful arc of HH 222, the Waterfall Nebula.

I’ve been fascinated by the Waterfall ever since I first saw an image of it, and have only seen it – barely - once in my scope. Surprisingly, that sighting was from my semi-dark backyard just before dawn during a stretch of remarkably transparent skies last September. This is also when I had spectacular views of NGC 1999 and HH 1/2, but HH 222 was a much more difficult object to see. Even so, it was a thrill to detect it at all.

Fortunately, HH 222 is an easy star hop from NGC 1999. The DSS image below shows 222 between the red lines in the upper right corner of the frame with 1999 in the lower left corner. That puts 222 about halfway between 1999 and the bright, but sparse, open cluster NGC 1980.

HH 222.JPG

Also notice the prominent zig-zag line of stars to the immediate east of 222, which was a good place to start my final star hop. To further refine 222’s exact position, I looked for the two fairly dim stars just north and south of the Waterfall as well as a star near the northern end of the nebula. The brightest star is approximately magnitude 11, and the other two are mag 15-ish. I could see all three stars in my 28-inch scope at 408x, and so was able to exactly pinpoint the location of HH 222.

I could only detect the brighter northern half of the Waterfall, but given how light polluted the sky is from my home I was amazed to see any of it. Even though my SQM readings were in the mid-19’s, top-notch transparency made all the difference.

HH 222 sketch.JPG HH 222 sketch_invert.JPG

For a number of reasons, I haven’t had a chance to look for HH 222 since last September, but when I do I hope to see under much darker skies.

By the way, HH 222’s counterpart is HH 1041, as shown on page 10 of this 2013 paper by B. Reipurth: https://iopscience.iop.org/article/1.../146/5/118/pdf
This image also shows that the variable star V380 Ori – the same star that illuminates NGC 1999 - is the source of the stellar outflows that created both HH 222 and HH 1041. Reipurth’s paper is a good read too.

There’s lots to see in this small section of sky, so give it go, and let us know!

(ps – HH 222 was the subject of a thread in the Deep Sky Forum in 2013, but as far as I can tell has never been an Object of the Week.)

[obrazell]

Howard I think the declination is -06 not +06 for this object.

[Howard B]

Thanks for catching the typo!

[akarsh]

Hi Howard

The waterfall has been on my wishlist for a while. It is shocking that you were able to see it from a mid-19 MPSAS sky. I had anticipated it to be way harder than that. Thanks for putting this back on my radar.

Clear Skies
Akarsh

[Uwe Glahn]

Wow, that was a difficult challenge Howard. I tried the Waterfall with the 27-inch under very good transparency last new moon and report success.

I had the best results with mid size EP (4mm, 172x) and without any filter. The lane was best visible just south of the faint star at the northern end. I had the feeling that the eastern edge was better and harder defined while the western side was more diffuse. Furthermore a nearly stellar patch somewhat south of the lane was popping in and out of view. The larger HH structure far more south was also suspected but more difficult to see as a whole object.

sketch: 27", 172x, NELM 6m5+, Seeing III
HH222.jpg
home