Object of the Week February 17, 2013--- IRAS 09371+1212 [Frosty Leo Nebula]

IRAS 09371+1212 Frosty Leo Nebula

LEO

RA
09 39 53
DEC
+11 58 52

MAG 11 V

Type Proto PN

This bright Proto PN can be seen in most telescopes I have seen reports of it being observed in 6" and 8" scopes. It is a very unique object and was found by the IRAS survey as a very cold object in the far IR. It first appeared in the journals in 1985. In 1987 Forvelle found it to have H2O ice crystals in the nebula from the spectrum. He is the one who suggested the name Frosty Leo nebula for its being cold in far IR and for the H2O Ice crystals.

Hubble Image
Attachment 476

I have observed this peculiar nebula many times over the years with my old 25" and my 48" telescopes. I like to show it to people because its one of the few deep sky objects that show color well. It has a ruddy orange color to my eye that shows well. Be sure to use as high a power as the seeing will allow on this object to show its fine detail and color. It has a peanut shape in the eyepiece and a faint anse on each end on nights with good seeing. At low power it looks like a fuzzy elongated star to me. The images below look close to how it looks in the 48"and is close to the color that I see.

Attachment 477 Attachment 478

Let me know if you see the color in this unique icy nebula and ,

"GIVE IT A GO AND LET US KNOW"

GOOD LUCK AND GREAT VIEWING!

Extremely interesting object Jimi, thanks for the cool OOTW.

Last year I spent two nights with good to very good seeing and tried to separate the small but bright details. With 27" and 837x I could detect the two fainter lobes N and S and some detail around the inner part. I took no notice about the color. Perhaps the AP was to little to detect the color? But seeing colors was never my strong point.

27", 837x, fst 6m5+
Attachment 479

Excellent drawing Uwe! I see you used 837 X that is what I was talking about using high powers to see the faint detail in this object. I think that it is the best way to see the faint anse of this bipolar nebula. To my eye the color is really prominent. I looked at it twice last week on one night the seeing was bad and the color was not seen on the other night the seeing was average for here and the color was evident so I guess the color is seeing dependent.

This surprisingly bright PN from CSOG:

Attachment 480

Observed it twice in 2011 in my 12" SCT:

3 May, from dark southern France: "Quite bright patch, even in brightness with a very bright central part or a very bright central star, very prominent. Just not stellar, although the nebula looks like a large, faint star. Immediately to the NE is a mag. 12 star which is in the tip of an isosceles triangle of stars pointing SW with the base on the NNE side consisiting of two mag. 12 stars in a line from NW to SE."

7 March, from light polluted Netherlands: "A small, slightly NW to SE elongated patch, just not stellar without use of averted vision, slightly larger and brighter when using averted vision, slightly more round (less elongated), pretty bright.
Both a Lumicon OIII and UHC filter have no effect."

Victor did you see any color in your observations?

Quote:

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Originally Posted by Jimi Lowrey

Victor did you see any color in your observations?

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No, just a grey patch. But I didn't actively compare the PN to stars in the vicinity as I do when observing double stars or carbon stars to determine color, or hue (if any).
I will try again in early April from the same spot in France and I will play around with magnifications a bit, looking for color. Will report back!

Hi Jimi,

good choice! I have observed this proto-PN several times, but I never looked for color. I will check this out next time. Color is likely most prominent at low power and I always tried to get to the highest possible power.

My up to now best observation was as follows:

Frosty Leo (IRAS 09371+1212) revealed at 550x a very small elliptical disk elongated in NW/SE direction. During moments of steady seeing, there is a hint of the bi-lobal structure visible in the HST image.


Proto-PN shine by definition in reflected light. Hence there is a fair chance to detect polarization (quite obvious for other proto-PN such as the Egg Nebula and Minkowski's Butterfly). As the nebula is relatively bright, I tested this one as well for polarization. However, no clear angle-dependent attenuation of the nebula could be observed in comparison to the neighboring star.

Reiner,

What Kind of a filter do you use to test for polarization and who makes the best one?

Hi Jimi,

I have no idea, which are the best ones. I have two of them, both linear polarization filters in 2" filter mounts. One is an old one from Hoya, the other one is from Edmund Optics
http://www.edmundoptics.com/optics/p...-filters/52559

Here is more about my attempts to detect polarization from protoPN and other objects
http://www.reinervogel.net/artikel/polarisation_e.html

(the section on Frosty Leo needs to be updated)

Color in Frosty Leo is quite evident in very evident in real large scopes, but I didn't note it in my 18" back in '96. Here are my last two observations...

48" (4/2/11): at 375x (unfiltered), Frosty Leo appeared as a compact bi-polar nebula containing two knots oriented NNW-SSE. The brighter knot was at the SSE side with the slightly smaller and fainter condensation on the NNW side. Both knots had a slightly irregular outline and were encased in a small common halo that extended ~25"x18". The nebula clearly had a dark orange or ruddy appearance. Located 0.9' SSW of a mag 12.6 star.

33" (2/19/09): very compact, but clearly non-stellar double nebula with two close condensations, appearing like an out of focus pair of mag 12 stars. The southern knot was slightly larger and brighter and the knots were slightly irregular in shape. Also unusual was a definite reddish tint to the nebula.

Steve,

I wounder if your new 24" will show the color? I have seen color in the Frosty Leo with my old 25" F/5 on good nights.

I've only had one look at Frosty Leo with my 28 inch so far and it was on a night of poor seeing. Here are my notes and sketch:

"The seeing is pretty soft so I can't see much shape in Frosty Leo - what a great name! - but I do see an elongated core that may be two areas in contact, with a small, tightly bounded faint envelope surrounding it. There's a galaxy nearby, NGC 2958, that's a touch southeast that I mistook for F.L. at first but it seemed too big. Also, F.L. has a faint but unmistakably light blue hue at low power (155x) but it's gone at 408x. (April 30, 2011) 10:54pm, 21.12 SQM."

Attachment 483

Thats interesting that it looked Bluish at low power. I think the color is effected by the seeing.

Finally an object were I can contribute! I've seen this object quite a few times in my 63mm Zeiss refractor. Once I observed it from indoors, looking out a glass door! And it was still easy to see. It is small and elongated at 120x, but very clearly nonstellar. The double core is definitely visible in a 94mm refractor at 520x and there was a hint of other details, but the conditions were unstable and I did not make a drawing.

I am fairly sure the double core must be visible in a 63mm, using 300x - 400x. I'll try it, if it ever clears. My list of things to check is getting horrifyingly long, but the clouds never seem to part.


Clear skies!
Thomas, Denmark

Visited this PN last night, 12" SCT under very good conditions. The nebulae was obvious, elongated and non-stellar. No color at 179x, pretty much the same image at 277x. At 436x the elongated, faint outer part became more obvious but remained gray. At the (intentionally) too high magnification of 610x it had a hint of greyish-green, not unlike M57 in 8" scopes. Speaking of M57, that PN was distinctly bluish green earlier this week using the same scope at 179x. M57's central star remains elusive for me.

I have worked on “Frosty Leo” for two nights using my 25” f 4 Dobsonian. In the first night (with good seeing at 700m) I could clearly separate the two bright lobes at 350x and 500x. The southern half appeared a little brighter and larger than the northern half. But I was unable to see the halo and ansae. In the second night (with good transparency but mediocre seeing, at 950m) I used higher magnifications (720x and 1000x), which made the dark channel between the lobes blur out completely. But the northern wing, especially the ansa, showed up momentarily now, if extremely weak. The southern wing remained invisible. Although I cecked for it, I could not perceive any color in “Frosty Leo”.

Johannes