Object of the Week April 21, 2013 - M51

[Howard B]

The Whirlpool Galaxy, NGC 5194–5195, Arp 85

Canes Venatici

RA
13h 29m 52.7s

DEC
+47° 11′ 43

Type: Interacting galaxies, B magnitudes 9.0 and 10.5

168 years ago, in April 1845, Lord Rosse discovered the spiral structure in M51 so I propose we honor Lord Rosse’s landmark discovery by not only appreciating the overall structure and beauty of M51 but to delve deeper and enjoy some of its more elusive delights, such as:
1. The dust lanes that define the inner edges of the spiral arms are much more subtle than photos suggest and require the most transparent nights to see. But not the darkest – my best view of them was on a 21.25 SQM night at 7200 feet with superb transparency.
2. The super star clusters near the core appear stellar at high power and help define the two-pronged beginning of the southern spiral arm. It takes steady seeing and high power for these tiny glimmers to sparkle into visibility.
3. HII regions help define the brightest parts of both spiral arms. I've found that high power is best even if the seeing isn't very steady.
4. The spiral arm spurs that connect the northern and southern.
5. Following both spiral arms all the way into the core is more difficult than I thought, again needing exceptional transparency.
6. How many of NGC 5195’s tidal tails can you see?
7. Has anyone seen IC 4277 as an edge on background galaxy? What magnitude is it? I've barely been able to see its core just east of NGC 5195.
8. And my new favorite, that until recently I assumed was an HII region of NGC 5195. Jimi pointed out it’s actually a distant background galaxy, 2MASXi J1330023+471654. I tried unsuccessfully for the past three years to see it with my 28 inch scope – so it’s not shown in my sketch - but Jimi, Steve Gottleib, Jim Chandler and I saw it through Jimi’s 48 inch earlier this month. Has anyone else seen this surprisingly elusive galaxy through NGC 5195?

M51 for Hawaii presentation.jpg M51 for Hawaii presentation_inverted.jpg

M51 OOTW_4-21-13.jpg

“GIVE IT A GO AND LET US KNOW”
GOOD LUCK AND GREAT VIEWING!

[Ivan Maly]

Great choice, Howard. So far I have seen 1 (dust lanes), 3 (HII regions, or as I call the large ones that I have seen, star clouds), and 4 (spiral arm spurs - the eastern one clearly).

As far as dust lanes, I found helpful the extreme dark adaptation that is achieved naturally as clouds pass over a dark location. This is assuming that you are tracking M51 and the transparency is good once the clouds pass. The attached sketch may look strange but it is quite precise as far as the appearance of the dust lanes that night. Both arms indeed appeared cleanly split along the middle, except where dense star clouds made them appear thicker. It was an unusual view and not my best view of M51 in general, but it has so far been my best view of the dust lanes. I just had to track M51 as the clouds were passing and be prepared to observe immediately when they cleared. I almost never observe unless it is completely clear, but this and a few similar experiences made me interested in further experimentation with extreme dark adaptation.

16", up to 225x, blue zone site, 2400 ft. I did not measure it on that night but 21.7-21.9 by SQM-L is typical there (Cherry Springs, PA).

M51 2011-04-21 inverted corrected.jpg

[Jimi Lowrey]

Here is the Hubble image of NGC 5195 zoomed in and inverted that shows the 2MASX galaxy #8 "The little goober". It looks like it is interacting and is being pulled apart.

cutout_hlsp_heritage_hst_acs-wfc_m51_f555w_v1_drz_sci(2).jpg

I was surprised at how it looked in the eyepiece it was not a stellar knot like it looks in deep images but was a diffuse soft round glow that was just a little brighter than the foreground NGC 5129 galaxy. I think it will be easer for Howard to see it in his 28" now that he knows what to look for.

[Jimi Lowrey]

Howard could you post a inverted image of your fantastic drawing of M51?

[Uwe Glahn]

Howard,

what a fantastic drawing, one of the most beautiful and above all one of the most realistic I ever saw - great result.

Funny, my plan was also to observe and to sketch M 51 with my 27" this spring but the worst weather period I remember prevent this. I only got a quick view of this galaxy last clear night. To your points.
1. You are absolutely right, the dust lanes are a difficult detail.
4. I missed the connection with 14,5", Rainer Mannoff saw it with 18", with 27" easy but not really prominent
6. With 14,5" I only saw one large glow, no streamers, with 27" I did not manage to look for it
7. Yes, I saw it last night but I could not hold it steadily. I was able to see the elongation but not with this extreme proportion. The IC catalog says 16,5bmag / 15,7vmag. The biggest problem is the elongation. After my experiences with a lot of "Superthin Galaxies" these mags are hard to detect visually.
8. I don't tried it yet.

My goal in the past was to see what could be possible with different aperture so a tried to sketch M 51 several times. Here my results:

4", 88x, NELM 6m5+
M51_4.jpg

7", 159x, NELM 7m0+
M51_7.jpg

14,5", 202x, NELM 6m5+
M51_14.jpg

Last but not least the wonderful sketch of S. Hunter with the 72" of Lord Rosse during the year 1864
M51_Hunter.jpg

[Howard B]

Howard could you post a inverted image of your fantastic drawing of M51?

I added the inverted drawing to my original post, good idea Jimi.

By the way, I should have mentioned that the view of M51 through Jimi's 48 inch scope a few weeks ago was - at first glance - at least twice as detailed as my drawing, which currently has about 8 hours of eyepiece time into it with my 28 inch. With a bit of time to study the 48 inch image the amount of detail was astounding! I could have observed M51 all night...

I'll continue to pursue the 2MASX galaxy (#8) with my 28 but I know I'm going to need exceptionally good transparency to have a chance because it was subtle even in the 48 on a pretty good night.

[Howard B]

Howard,

what a fantastic drawing, one of the most beautiful and above all one of the most realistic I ever saw - great result.

Funny, my plan was also to observe and to sketch M 51 with my 27" this spring but the worst weather period I remember prevent this.

Thanks Uwe, I'm really proud of this sketch. I also hope to have several good chances this spring to observe M51 but like you the weather so far has not been cooperative, although I did have half a night in March that was good enough that I added a few details to my drawing. Your drawings are excellent as well, I especially like the one made with a 4" scope that shows the spiral arms as a ring - just like the Herschel's saw it!

Good luck to everyone for some clear skies this spring.

[Howard B]

Great choice, Howard. So far I have seen 1 (dust lanes), 3 (HII regions, or as I call the large ones that I have seen, star clouds), and 4 (spiral arm spurs - the eastern one clearly).

As far as dust lanes, I found helpful the extreme dark adaptation that is achieved naturally as clouds pass over a dark location. This is assuming that you are tracking M51 and the transparency is good once the clouds pass. The attached sketch may look strange but it is quite precise as far as the appearance of the dust lanes that night. Both arms indeed appeared cleanly split along the middle, except where dense star clouds made them appear thicker. It was an unusual view and not my best view of M51 in general, but it has so far been my best view of the dust lanes. I just had to track M51 as the clouds were passing and be prepared to observe immediately when they cleared. I almost never observe unless it is completely clear, but this and a few similar experiences made me interested in further experimentation with extreme dark adaptation.

16", up to 225x, blue zone site, 2400 ft. I did not measure it on that night but 21.7-21.9 by SQM-L is typical there (Cherry Springs, PA).

M51 2011-04-21 inverted corrected.jpg

Hi Ivan,

That's interesting because my best ever view of M51 came on a night in central Oregon with passing clouds - the sky between the clouds was nearly perfect, at least until they took over the sky. This was the view that made me promise to make as a good a drawing of M51 as I could, and in the 5 years since then I have not had a sky as dark, transparent and steady as that partly cloudy night. I didn't have a SQM at the time and I haven't been back to that specific spot since, but it is in a grey zone.

Your observation of the dust lanes is really impressive. I've tried several times with Chuck and Judy Dethloff's excellent 16 inch but have not seen them in that scope yet. I have seen a couple of the star-like super clusters near the beginning of the southern spiral arm in that scope though.

[Ivan Maly]

Great sketches, Uwe, and thanks for posting the historical Hunter drawing.

I will try for these superclusters, Howard. Thank you for the tip.

The other explanation for the effect of (or correlation with) the clouds may be that when passing they "scrape" the sky and leave it unusually transparent. This of course is known for large passing fronts, but I am not certain it is true for the kind of "iffy" weather in our two cases. I actually did not think transparency in the wake of the clouds was unusually good on the night I mentioned, but then I was too busy absorbing the view through the eyepiece to estimate it. It may be a combination of the two factors (dark adaptation under the clouds and "scouring" of the sky by the clouds).

I find the dust lane in the arm segment S of the core comparatively easy. It is the only clear-cut dust lane segment that I have seen on other nights. In the drawing below, S is to the upper right. It was made after a night-long observation when the supernova of 2011 was near its peak, with the same telescope (16"), magnifications, and from the same site. The texture shown was general perception only, not actual detail.

2011dh-IVM.jpg

The split and gap in the outer arm E of the core (in the arm segment pointing at NGC 5195) in this view comes from some combination of the inter-arm spur and the actual dust lane in the outer segment there. And of course the visible notch in NGC 5195 is due primarily or exclusively to the continuation of the dust lane of NGC 5194 superimposed on the companion!

[RolandosCY]

On May 9 and 10 I will be taking a short vacation at a tiny hotel right at the edge of a grey zone on Cyprus (last March I got readings of around 21.10 from the hotel yard, imagine without the lights). If the weather is good I will take my 18", and since I will have to observe from the (very dark) hotel's backyard (I promised my wife I will not disappear in the middle of nowhere!) sketching M51 with the 18" sounds a fun project. Thanks for the heads'up for a wonderful object...

[Ivan Maly]

Saturday night I managed a quick look at M51 with the same scope from the same site. At 300x with a ZAOII-6, two of the brightest and largest HII regions were visible. They were cataloged by Carranza, Crillon, and Monnet in a 1969 Astronomy and Astrophysics paper (1:479) as #71 and 72. I refer to this catalog as "CCM".

On the photographic chart in Stoyan's Atlas of the Messier Objects they (or their starlike cores) are labeled L 203 and L 180. I was unable to determine the origin of these "L" designations or what type of objects they represent.

CCM 71 was labeled as such on Howard's sketch in his July 2011 S&T article. Based on location, I am certain that the much more compact object to its NW in Howard's sketch is CCM 72, although the difference in size between it and CCM 71 in his sketch is greater than in my view.

At 225x I saw the starlike center in 71 flickering in the center of a compact nebulosity that has a weak narrow extension terminating around the position of CCM 72. At 300x, the two objects were fully resolved and looked similar in brightness and size, 72 still being more prominent and each exhibiting a starlike center surrounded by compact, strongly concentrated nebulosity.

16", Cherry Springs, good seeing, poor transparency, 50% humidity, 12C, 200-300x, north up, west right
2013-04-27 M51 labeled.jpg

[kisspeter]

Amazing observations above! Especially Howard's drawing with 28". I've never seen M 51 in such detail. And I haven't seen many deep-sky drawings of such quality and precision.

I include my observation with a 16" from Hungary which I processed a couple of days ago:

16", f/4.4, 176x, 2014.03.28-30. Ágasvár, Hungary:
m51-v2-composite-curves_retouch_crop-1.jpgm51-v2-composite-curves_retouch_crop_positive.jpg

And an older drawing with 4":
m51_10T_crop.jpg

Concerning the details mentioned above I haven't seen many of them:
(1) dust lanes - not really seen, arms not perfectly homogenious but no dust lanes
(3) HII regions - the brightest ones were visible
(4) one connection between the arms partially visible

What I would be interested in is the visibility of IC 4278, the brighter background galaxy. What is the smallest aperture that you have seen the galaxy with? I tried it hard with 16" (neither scope not sky were abslutely perfect) but it was negative.

[Howard B]

Hi Peter,

The smallest scope I've seen IC 4278 is a 20 inch, and it's much easier to see than the edge on IC 4277, but I (barely) managed that with a 20 inch too. My friend Chuck Dethloff has seen 4278 with a 16 inch though.

[kisspeter]

Thanks Howard.
Based on its magnitude (15.4m) and size (0.5') I guessed it should be visible with a 16" scope. But it's very hard at least.

[wvreeven]

A new challenge has been discovered near M 51: A Hanny's Voorwerp-like object! I am not sure if this is feasible visually, but full details can be read in this paper:

https://arxiv.org/pdf/1804.01699.pdf

I hope the authors of the paper won't mind if I post an image taken from their paper here for easy reference:

M51_Voorwerp.png

[Howard B]

This looks something for Jimi to tackle!

[starwave]

There are some very nice drawings and observations here for Messier 51 AKA the Whirlpool Galaxy.

Last night at 22:30hrs (UT) I was looking at M51 through my C9.25 XLT Fast Star and 2" Skywatcher LPR filter and TS 2" prism diagonal.
Here in Cheshire - England. We had an unusually clear night. It was very transparent, with excellent seeing. ANT I, I estemated the NLM at +4.3.

Messier 51 is now riding high at the Zenith. So I have very little atmosphere to see through.

24mm Panoptic X 97. Bright and stellar with NGC 5195 also visible though fainter.

I then boosted the magnification to x180- Baader 13mm Hyperion. M51 was faint at first. But I could now see faint dust lanes with averted vision when my eye had settled and adapted to the darker field.

Switching to my older 35mm Celestron Ultima (x67)
M51 looked like a galaxy should look. The arms were clearly visible with averted vision. And NGC 5195 was also more defined.

This eyepiece gave me the best view of M51, that I have had.