Object of the Week, October 6, 2013 - NGC 604

NGC 604

Triangulum

RA
01 hour, 34 minutes, 32.8 seconds

DEC
+30 degrees, 47 minutes, 06 seconds

Type: Extra galactic HII region, size 1.93 arc minutes x 1.2 arc minutes


NGC 604 is almost as interesting as all the rest of M33. Why would I think that? First of all, 604 is the largest and brightest HII region in M33. Visually, it has the highest surface brightness of anything in M33 and in actual size is approximately 1500 light years across its longest dimension. Seen from 3 million light years away it's still a pretty impressive sight. For a sense of scale, consider that M42 in our own galaxy is about 24 light years across and about 1344 light years away – a distance smaller than the width of 604!

Attachment 917

Observers with even moderately dark skies and a scope 12 inches or larger will find that 604 is more than a shapeless blob. I first started observing 604 with a 20 inch scope years ago and was immediately struck by what appeared to be two overlapping triangles of nebulosity. It took about 250x for the shapes to be apparent and they become easier to see with increasing magnification, a benefit of 604’s high surface brightness.

If you have a dark sky you might also notice a fainter fan of nebulosity curving away from the brighter triangle, and a slightly fainter halo around both triangles. Although I've tried my best to see the arc as shown in the HST image above, I've so far come up short. However, Jimi has seen it with his 48 inch scope.

Attachment 918 Attachment 919

This is my latest sketch from the 2013 Oregon Star Party on a night with consistent SQM readings of 21.85 and excellent seeing. Using around 700x, small stellar points glimmered into visibility. I've been able to boost magnification to 1250x with my 28 scope to best see them. I’m not sure if I’m seeing individual stars in 604, because they could be compact groups of stars or highly compressed parts of the nebulosity, but each time I see them I’m astonished to be able to detect this level of detail from 3 million light years away.

“Give it a go and let us know!”

Good luck and great viewing!

(PS, sorry for the late post!)

Howard,

one of my favorites which I visit very often. I have a small project (DS challenges) on my website which is only in German. I try to translate my experiences with this object.

First look inside NGC 604 gave my Frank Richardsen in his 20" around 10 years ago. In his scope several spots were visible which fascinated me. After that I tried the object with lots of scope stuff and waited the best Seeing conditions I could get to resolve as much star cluster I could.

10x50; NELM 6m5+
not visible, star GSC 2293642 1' SE easy visible but not the HII region

4", 63x-113x, NELM 7m+
NGC 604 easy visible, a little bit concentrated to its middle (sketch)

20", 830x, NELM 7m+, Seeing II
four spots are visible with averted vision, form of a triangle, fifth spot pops in and out of view

27", 837x, NELM 7m+, Seeing I-II
shocking resolution of the central triangle into four spots; altogether 14 spots could be resolve, perhaps a few foreground stars; no nebulous detail, no positive filter reaction; perhaps AP to small

Attachment 921
inverted version

I spoke with several people who also observed this central triangle. I think you have it also on your sketch. To resolve this triangle you need very good seeing, which seems to be more important than aperture (I know some sketches and observation with 32" and 44")

Funny, I was thinking yesterday of suggesting this object as an OOTW. I've observed it recently quite a few times in my 12" dob. The scope has very poor optics, unfortunately, but still I'm able to begin to glimpse mottling and some uneven shape in this fascinating object. I've seen it in scopes as small as a 50mm Zeiss refractor and regularly see it in my 63mm Zeiss. I tried for it with a 42mm refractor, but couldn't see it. In a 5" f/14 refractor at 140x, I distinctly saw its irregular elongated shape and hints of mottling.


Clear skies!
Thomas, Denmark

The first time I looked at NGC 604 with the 48" was last year I was shocked at seeing the loop in the nebula. Has anyone else seen this feature in NGC 604? I was using 813x on a night of good seeing.

Image showing the loop,
Attachment 926

In the night between 2./3. September i was having the first light of my reconstructed and re-mirrored Obs 25". With my friends Riku and Timo we observed for example two stars inside the ring of M57, failed to detect nearby IC1296. But I got a drawing of NGC 604. Very intriguing target indeed.

Attachment 2237

I saw angular shapes and dark ditches inside the glow as well the outer shape was somewhat angular for me. Several twinkling pinpoints of sparks, difficult to count and locate precisely. A tiny glow with stellar like core east of the star GSC 2293:642 as in the drawing. What this object may be?

-Markus

Better late than never I guess, so here's my impressions on NGC 604 the same night and instrument mentioned by Markus above.

"A bright nebula easily spotted in same low power field as M33. Nebula is elongated about 2:3 in N-S direction, and has somewhat boxy appearance. Superimposed on top of nebula is a string of stars on the north side. Some more stars in the area of nebula can be resolved too, altogether about 8 to 10. The prominent star string runs on W-E direction across the nebula. The whole nebula seems granulated, as if on the brink of being completely resolved into stars. Some mottling visible as well, but exact structure is hard to pinpoint. Star association A85 is seen starlike on E-side of the sketch. Magnificient object with all the details."

Attachment 2238

Here's a link to the original observation with all the details: http://www.deepsky-archive.com/record.php?id=11113

____________

Riku Henriksson
Kylmakoski, Finland

Quote:

---

Originally Posted by MakeTT

In the night between 2./3. September i was having the first light of my reconstructed and re-mirrored Obs 25". With my friends Riku and Timo we observed for example two stars inside the ring of M57, failed to detect nearby IC1296. But I got a drawing of NGC 604. Very intriguing target indeed.

Attachment 2237

I saw angular shapes and dark ditches inside the glow as well the outer shape was somewhat angular for me. Several twinkling pinpoints of sparks, difficult to count and locate precisely. A tiny glow with stellar like core east of the star GSC 2293:642 as in the drawing. What this object may be?

-Markus

---

Markus, that is a star cluster in M33. It is plotted as the 14.6 magnitude star GSC 2293:654 in MegaStar but deep photos show that it's actually the star cluster [CBF2001] 142 (=[PL2007] 238, [SM2007] 420), 0'.8 SE of the bright 10.9 mag field star. V-magnitude 15.9. You can see the cluster in

http://news.sky-map.org/?img_source=...&box_height=50 (zoom out)

http://archive.stsci.edu/cgi-bin/dss...e&fov=NONE&v3=

The object is also visible as a blue cluster with a brighter central star in Jimi Lowrey's image above.

Entry in NED: http://ned.ipac.caltech.edu/cgi-bin/...=0.73&corr_z=1

A good catch, Markus!

/Timo Karhula