Medusa Nebula

This article is about a planetary nebula. For the Medusa Galaxy Merger, see NGC 4194.

The Medusa Nebula is a planetary nebula in the constellation of Gemini. It is also known as Abell 21 and Sharpless 2-274. It was originally discovered in 1955 by University of California, Los Angeles astronomer George O. Abell, who classified it as an old planetary nebula.^[4] With the computation of expansion velocities and the thermal character of the radio emission, Soviet astronomers in 1971 concluded that it was most likely a planetary nebula.^[4] As the nebula is so large, its surface brightness is very low, with surface magnitudes of between +15.99 and +25 reported.^{[citation needed]}

Medusa Nebula

Emission nebula
Planetary nebula
Medusa nebula, Mayall Telescope
Observation data: J2000.0 epoch
Right ascension	07h 29m 02.69s[1][2]
Declination	+13° 14′ 48.4″[1][2]
Distance	1,500 ly (460 pc)[3] ly
Apparent magnitude (V)	15.99[1]
Apparent dimensions (V)	10.25 x 10.25 arcmin[1]
Constellation	Gemini
Physical characteristics
Radius	4 [3] ly
Absolute magnitude (V)	7.68
Notable features	Very large & very low surface brightness
Designations	Sharpless 2-274, PK 205+14 1, Abell 21 [1]
See also: Lists of nebulae

The central star of the planetary nebula is a PG 1159 star.^[5]

See also

• Abell Catalog of Planetary Nebulae　　　　　　　　　　　
• Geminga, Gemini gamma-ray source
• Gemini in Chinese astronomy
• IC 444, reflection nebula
• Messier 35 open cluster
• Cancer Minor (constellation) - Obsolete constellation inside modern Gemini