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Does anyone know what the blue object below the Garnet Star in the Elephant Trunk Nebula (IC 1396) is? This is with Ha-OIII narrowband and I have increased the saturation of the blue a bit so it is actually probably more of a blue-white colour. I presume it is a reflection nebula? This is a 327mm focal length with an ASI2600 so the pixels are 2.36" in size so the object is maybe 60 arcsecs across?   |
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GM 3-13, a PN.
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andrea tasselli: Lovely. Thanks. |
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Thanks @andrea tasselli That identification got me to this thread: https://www.cloudynights.com/topic/846834-gm-3-13-planetary-nebula-in-cepheus/ which suggests (after some back and forth) that it may be PM 1-333
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Or possibly https://app.astrobin.com/i/0dolq1 " In SIMBAD, this object is known as PN G100.4+04.6 (a “possible planetary nebula”), while in NED it is surprisingly known slightly differently as PN G100.5+04.7" Anyway, a nice little gem.
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The last two refer to the PN's galactic coordinates so little surprise in a slight difference in the PN/s coordinates (which may either identified by the originator white dwarf or its photometric barycentre)
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Yes - Simbad has the following: At coords (J2000.0) 21:40:59.32176 +58:58:38.7768: |
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I will point a 9.25" SCT at it tonight and see what I can see. Thanks for the help.
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Another thread mentions a paper (frustratingly not giving the citation) that suggests it is mainly emitting He II/Hß. But I captured it in the OIII frequency with a 3nm bandwidth (Optolong L-Ultimate). This is why I love this hobby - find a little weird blob on an image and dive down a deep rabbit hole. https://www.cloudynights.com/topic/494333-pn-g1004046pm-1-333-a-strange-looking-planetary/ Edit - found the paper I think: http://doi.org/10.1088/0004-6256/137/5/4140 |
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Andrew Rambaut: Given the spectra I guess they were wrong. HeII emission while there is weak, with the two strangest emissions being in the OIII and the Ha ones, IOW a typical bi-lobed PN, see: SPECTROSCOPIC CONFIRMATION OF THE PLANETARY NEBULA NATURE OF PM 1-242, PM 1-318, AND PM 1-333 AND MORPHOLOGICAL ANALYSIS OF THE NEBULAE - IOPscience |
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Given the tight bandwidth for OIII on my filter (and how bright the object is in this frequency) I agree with you - the main emission must be OIII - that would accord with Table 2 in the paper - so I guess when they say "PM 1-333 is an extended planetary nebula with a high-excitation (He iiλ4686/Hβ up to ∼ 0.9) patchy circular main body containing two low-excitation knotty arcs. A low Ne([S ii]) of ∼ 450 cm−3 and Te([O iii]) of ∼ 15000 K are derived for this nebula. " in the Abstract they mean that these are the unusual features.
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A cosmic fish !
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Yes - I was thinking the Parrotfish Nebula!  |
