Peanut Nebula (NGC 2371/2)

NGC 2371/2
NGC 2371/2: Peanut Nebula in Gemini; 500 mm Cassegrain 5800 mm f/11.4; SBIG STL11K; 80+15+15+15 min LRGB; Bernese Highlands; © 2005 Radek Chromik [32]

Object Description

The nebula was discovered on 12 March 1785 by William Herschel. But he spotted two separate nebulae and cataloged them as II 316 and II 317 (class II = faint nebulae). He described them as follows: «Two, south preceeding north following, distance 1' chevelure mix. Both faint, small, equal, having a nucleus or bright compressed spot». [463] Those later became NGC 2371 and NGC 2372. In 1917 it was identified as a planetary nebula by Francis G. Pease. [141]

At first glance, the elongated or even two-part structure is particularly striking. This is the reason why there are two entries in the NGC catalog for this object: 2371 and 2372. The outer ends, which are brighter than the inner area, can under certain circumstances simulate the double nature. In reality, however, it is one and the same planetary nebula - this is confirmed in the 20 cm reflector but probably also in smaller telescopes. The sight most closely resembles a peanut, for lack of another name I call NGC 2371/2 the Peanut Nebula.

NGC 2371/2
NGC 2371/2: Inner area; 500/2500mm-Newton + SBIG ST-6; Observatory Bülach; © 1996 Stefan Meister

In the Vorontsov-Velyaminov classification system, the form is given as IIIa+VI. IIIa stands for an irregular disk with a very uneven brightness distribution and refers to each of the two halves; VI means that the nebula has an anomalous shape, this applies to the whole object.

At around 10'000 years old, this is a relatively old planetary nebula. Despite its age, the surface temperature of the central star is still around 100'000 Kelvin.

Figure 1 also shows the outer areas. Are these denser regions of an older shell, or is there a bipolar stellar wind emanating from the central star that is causing large parts of the nebula to expand more?

— 1996, Philipp Reza Heck

«Strasbourg-ESO Catalogue of Galactic Planetary Nebulae» Acker et al., 1992 [141]
Designations PN G189.1+19.8: NGC 2371-72, PK 189+19.1, ARO 45, VV 37, VV' 61
Right Ascension (J2000.0) 07h 25m 35s
Declination (J2000.0) +29° 29' 36"
Dimensions 44." (optical)
Distance 1.64 kpc
Radial Velocity +20.6 ± 2.7 km/s
Expansion Velocity 42.5 (O-III) km/s
C-Star Designations AG82 80
C-Star Magnitude U: 13.28, B: 14.48, V: 14.85
C-Star Spectral Type O VI, WC early
Discoverer PEASE 1917

How to find the Peanut?

This object is extremely easy to find even without a Telrad finder: Adjust the 3.8mag star Propus (ι Geminorum) and swivel 1° 40' in declination to the north and the nebula should already be in the field of view of a low power wide-angle eyepiece. The best viewing time is October to April.

Finder Chart Peanut Nebula (NGC 2371/2)
Peanut Nebula (NGC 2371/2) in constellation Gemini. Charts created using SkySafari 6 Pro and STScI Digitized Sky Survey. Limiting magnitudes: Constellation chart ~6.5 mag, DSS2 close-ups ~20 mag. [149, 160]

Visual Observation

NGC 2371/2
NGC 2371/2: Zeichnung; 200mm SCT; © 1996 Philipp Reza Heck

200 mm aperture: With a magnification of 140x, the «peanut shape» comes into its own in the 8-inch model. You can also see some structure in the nebula. The western half appears somewhat brighter and larger than the eastern. In addition, I had the impression that the western part of the nebula is overlaid by a star. However, it is not the central star, which is located between the two halves at almost 15th magnitude and can also be seen on the CCD image of the inner area (see Fig. 2). Even if NGC 2371/2 does not appear very bright at medium magnification, it is worth zooming in. The resolution of the eye is much lower in dim light. It is therefore necessary to magnify to see details. At 226x, despite the moon (approx. 36 percent), I recognized significantly more structure than at 140x. — 1996, Philipp Reza Heck

762 mm aperture: Without a nebula filter (first tried with UHC) the Peanut Nebula NGC 2371 shows both bright parts of the nebula as one peanut each. The central star in between only became really visible without a filter. — 30" f/3.3 Slipstream Dobsonian, Hasliberg Reuti, 5. 3. 2022, Eduard von Bergen

Objects Within a Radius of 15°