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NGC 2371
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NGC 2371 (also NGC 2372 and PK 189 +19.1) is a magnitude +13.0 lobed planetary nebula located 4,400 light-years away in the constellation Gemini.
Visible the nebulas bipolar morphology suggests that the two condensations of material are part of a torus of gas. The central area is illuminated by a hot star of magnitude +14.8 which has a surface temperature of 118,000 Kelvin. Narrow-band filters, especially an OIII filter, can help with observing the planetary nebula.

The nebula was discovered by German-British astronomer William Herschel using a 47.5 cm (18.7 inch) f/13 speculum reflector at Datchet, Berkshire,on the 12th March 1785.
The nebula was rediscovered by William Herschel on the same night and relisted as NGC 2372.

Right Ascension 07h 25m 33.9s, Declination +29 29 18"

Visually, it appears like it could be two separate objects; therefore, two entries were given to the planetary nebula by William Herschel in the "New General Catalogue", so it may be referred to as NGC 2371, NGC 2372, or variations on this name
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Title: The Structure of the Planetary Nebula NGC 2371 in the Visible and Mid-Infrared
Authors: G. Ramos-Larios, J. P. Phillips

We investigate the structure of the planetary nebula (PN) NGC 2371 using [OIII]-5007 imaging taken with the Jacobus Kapteyn 1.0 m telescope, and [NII]-6584, [OIII]-5007 and Ha results acquired with the Hubble Space Telescope (HST). These are supplemented with archival mid-infrared (MIR) observations taken with the Spitzer Space Telescope (Spitzer). We note the presence of off-axis low-ionisation spokes along a PA of 65 degrees, and associated collars of enhanced [OIII] emission. The spokes appear to consist of dense condensations having low-excitation tails, possibly arising due to UV shadowing and/or ram-pressure stripping of material. Line ratios imply that most of the emission arises through photo-ionisation, and is unlikely to derive from post-shock cooling regions. An analysis of these features in the MIR suggests that they may also be associated with high levels of emission from polycyclic aromatic hydrocarbons (PAHs), together with various permitted and forbidden line transitions. Such high levels of PAH emission, where they are confirmed, may develop as a result of preferentially enhanced FUV pumping of the molecules, or shattering of larger grains within local shocks. Although H2 emission may also contribute to these trends, it is argued that shock-excited transitions would lead to markedly differing results. We finally note that thin filaments and ridges of [OIII] emission may indicate the presence of shock activity at the limits of the interior envelope, as well as at various positions within the shell itself. We also note that radially increasing fluxes at 3.6, 5.8 and 8.0 microns, relative to the emission at 4.5 microns, may arise due to enhanced PAH emission in external photo-dissociative regions (PDRs).

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The object, called NGC 2371, is a planetary nebula, the glowing remains of a sun-like star. The remnant star visible at the centre of NGC 2371 is the super-hot core of the former red giant, now stripped of its outer layers. Its surface temperature is a scorching 240,000 degrees Fahrenheit. NGC 2371 lies in the constellation Gemini.

220877main_image_1054_946-710.jpg
Credit: NASA, ESA and the Hubble Heritage Team (STScI/AURA)

The Hubble image reveals several remarkable features, most notably the prominent pink clouds lying on opposite sides of the central star. This colour indicates that they are relatively cool and dense, compared to the rest of the gas in the nebula.

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