| Reflection nebula | |
|---|---|
| Protoplanetary nebula | |
 The Calabash Nebula, as taken byHubble Space Telescope | |
| Observation data:J2000epoch | |
| Right ascension | 07h 42m 16.83s[1] |
| Declination | −14° 42′ 52.1″[1] |
| Distance | 4,200[2] ly (1,300 pc) |
| Apparent magnitude (V) | 9.47[1] |
| Apparent dimensions (V) | 1′[citation needed] |
| Constellation | Puppis |
| Physical characteristics | |
| Radius | 0.7[a] ly |
| Absolute magnitude (V) | -1.4[b] |
| Designations | OH 231.84 +4.22,[1] Rotten Egg Nebula[1] |
| See also:Lists of nebulae | |
| Characteristics | |
|---|---|
| Evolutionary stage | OH/IR star[1] |
| Spectral type | M10III + A[1] |
| Variable type | Mira[1] |
| Database references | |
| SIMBAD | data |
TheCalabash Nebula, also known as theRotten Egg Nebula or by its technical nameOH 231.84 +4.22, is aprotoplanetary nebula (PPN) 1.4light years (13 Pm) long and located some 5,000 light years (47 Em) fromEarth in the constellationPuppis. The name "Calabash Nebula" was first proposed in 1989 in an early paper on its expected nebular dynamics, based on the nebula's appearance.[4]The Calabash is almost certainly a member of the open clusterMessier 46, as it has the same distance, radial velocity, and proper motion.[5] The central star isQX Puppis, abinary composed of a very coolMira variable and anA-type main-sequence star.
Violent gas collisions that produced supersonic shock fronts in a dying star are seen in a detailed image fromNASA'sHubble Space Telescope.
The object is sometimes called the Rotten Egg Nebula as it contains a relatively large amount ofsulphur. The densest parts of the nebula are composed of material ejected recently by the central star and accelerated in opposite directions. This material, shown as yellow in the image, is zooming away at speeds up to one and a half million kilometers per hour (one million miles per hour). Most of the star's original mass is now contained in thesebipolar gas structures.
A team of Spanish and US astronomers used NASA's Hubble Space Telescope to study how the gas stream rams into the surrounding material, shown in blue. They believe that such interactions dominate the formation process in planetary nebulae. Due to the high speed of the gas, shock-fronts are formed on impact and heat the surrounding gases. Although computer calculations had predicted the existence and structure of such shocks for some time, previous observations had not been able to prove the theory.
This new Hubble image used filters that only let through light from ionized hydrogen and nitrogen atoms. Astronomers were able to distinguish the warmest parts of the gas heated by the violent shocks and found that they form a complex double-bubble shape. The bright yellow-orange colors in the picture show how dense, high-speed gas is flowing from the star, like supersonic speeding bullets ripping through a medium in opposite directions. The central star itself is hidden in the dusty band at the center.
Much of the gas flow observed today seems to stem from a sudden acceleration that took place about 800 years ago. Astronomers believe that 1,000 years from now, the Calabash Nebula will become a fully developed planetary nebula.
In wide field images, the Calabash nebula is visible near the bright planetary nebulaNGC 2438 in deep photographs. Although the Calabash Nebula is at the same distance asM46, NGC 2438 is a larger object in the foreground.
