Calabash nebula

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Calabash nebula
Observational Data
Designation OH 231.84 +4.22
Right ascension 07h 42m 16.83s[1]
Declination -14° 42′ 52.1″[1]
Constellation Puppis
Type of object Protoplanetary nebula
Dimensions 1 arcminute
Magnitude Apparent Mag: +9.47[1]
Absolute Mag: -1.47[1]
Distance from Earth 4,200 ly[1]
Not to be confused with the Egg nebula

The Calabash nebula (OH 231.84 +4.22) is a protoplanetary nebula in the constellation of Puppis.[1] It is believed to be located in the open cluster Messier 46 since it lies at the same distance of 5,000 light years and also has the same radial velocity and proper motion.[1] The name Calabash was proposed due to its unusual shape.[2] The nebula is occasionally referred to as the "Rotten egg nebula" due to the large quantities of sulphur present in the nebula (sulphur often smells like rotten eggs when combined with various elements).[3]

Properties and Structure

The nebula is thought to lie approximately 5,000 light years from Earth.[3] However some sources put it lower at only 4,200 light years.[1] Therefore its apparent size of 1 arcminute corresponds to a physical size of 1.22-1.55 ly across.[4] It is thought to have a radius of 0.7 ly. There is a star at the centre of the nebula, though it is obscured by gas. It is thought to be surrounded by rotating gas in the shape of a torus (doughnut).[5]

Vast quantities of material are being ejected by the star at high speed in opposite directions. This has created the bipolar (two lobed) structure that is apparent in images of the nebula. The fastest gas is shown in yellow and is moving at over one million kilometers per hour (621,371 miles per hour).[3] When this gas slams into the surrounding interstellar gas, a supersonic shock front forms.[6] Sulphur containing molecules such as sulphur dioxide and hydrogen sulphide has been discovered through radio observations of the nebula.[1] These molecules are thought to have been formed by the supersonic shock.

The color of the gas in the nebula depends on its composition. Blue corresponds to ionized nitrogen and hydrogen.[6]


  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 Calabash Nebula (Rotten Egg Nebula) from
  2. Icke, V. and Preston, H. (1989). The dynamics of the Calabash Nebula. Astronomy and Astrophysics, 211(2), p.410. Bibcode:1989A&A...211..409I
  3. 3.0 3.1 3.2 Hubble Captures Brilliant Star Death in “Rotten Egg” Nebula from
  4. By direct calculation using distances of 4,200 and 5,000 ly.
  5. Demurs, J., Sánchez Contreras, C., Bujarrabal, V., Colomer, F. and Alcolea, J. (2001). Detection of an inner torus in the protoplanetary nebulae OH231.8+4.2. In: Cosmic Masers: From Proto-Stars to Black Holes. San Francisco: Astronomical Society of the Pacific, p.334. arXiv:astro-ph/0109543 Bibcode:2002IAUS..206..344D
  6. 6.0 6.1 The Calabash Nebula from Hubble from

External links