Red Rectangle Nebula

Not to be confused with Red Square Nebula.

Red Rectangle Nebula

Reflection nebula
Protoplanetary nebula
Hubble Space Telescope WFPC2 image of the Red Rectangle Nebula
Observation data: J2000 epoch
Right ascension	06h 19m 58.2160s
Declination	−10° 38′ 14.691″
Distance	2.3 ± 0.3 k ly   (710 ± 100 pc)
Apparent magnitude (V)	9.02
Constellation	Monoceros
Designations	HD 44179, RAFGL 915

The Red Rectangle Nebula, so called because of its red color and unique rectangular shape, is a protoplanetary nebula in the Monoceros constellation. Also known as HD 44179, the nebula was discovered in 1973 during a rocket flight associated with the AFCRL Infrared Sky Survey called Hi Star. The binary system at the center of the nebula was first discovered by Robert Grant Aitken in 1915.

Characteristics

Diffraction-limited speckle images of it in visible and near infrared light reveal a highly symmetric, compact bipolar nebula with X-shaped spikes which imply toroidal dispersion of the circumstellar material. The central binary system is completely obscured, providing no direct light.

On the 203rd Meeting of the American Astronomical Society in January 2004, information was reported by a team led by A. Witt of the University of Toledo, Ohio, that his team had discovered the spectral signatures of the polycyclic aromatic hydrocarbons anthracene and pyrene in the ultraviolet light emitted by the nebula - potentially vital organic molecules for the formation of life. Until recently, it was thought that the ultraviolet light would quickly destroy these hydrocarbons; the fact that the hydrocarbons still exist today has been explained by recently discovered molecular forces.

A likely explanation for its symmetry is that the central star - actually a close pair of stars - is surrounded by a thick dust torus which pinches the otherwise spherical outflow into tip-touching cone shapes. Because we view the torus edge-on, the boundary edges of the cone shapes seem to form an X. The distinct rungs suggest the outflow occurs in fits and starts. About 2,300 light-years away toward the constellation Monoceros, the Red Rectangle Nebula should be transformed into a planetary nebula as its cool central star becomes a hot white dwarf over the next few thousand years.

File:The Red Rectangle around the star HD 44179.jpg

Hubble Space Telescope ACS image. Broadband red light is shown in red, H-alpha emission is shown in blue

The Hubble Space Telescope has revealed a wealth of new features in the Red Rectangle that cannot be seen by ground-based telescopes looking through Earth's turbulent atmosphere. The origins of many of the features in this dying star still remain hidden or even outright mysterious. Some are well explained by theorists like the Dutch scientist Vincent Icke from Leiden University in the Netherlands.

In 1981 Vincent Icke and collaborators showed that a spherical gas ejection from a dying star hitting a dust torus would give rise to shocks that can produce cone-like outflows similar to the two cones seen in this nebula.

Of the many different parameters in Vincent Icke's calculations, only the density of the gas and the dust are observed in the nebula.

References

The Red Rectangle is a proto-planetary nebula

External links

• The remarkable Red Rectangle: A Stairway to Heaven?
• Dying Star Sculpts Rungs of Gas and Dust
• Charged polycyclic aromatic hydrocarbon clusters and the galactic red emission, 2007.
• Astronomy Picture of the Day – The Red Rectangle Nebula from Hubble (14 June 2010)
• The Red Rectangle