NGC 2261

NGC 2261
An image of NGC 2261 by the Hubble space telescope. Credit: HST/NASA/JPL.
Observation data: J2000.0 epoch
Type	Variable nebula
Right ascension	6h 39m 10s[1]
Declination	+8° 45′[1]
Distance	2.5 kly
Apparent magnitude (V)	9.0
Apparent dimensions (V)	2′
Constellation	Monoceros
Physical characteristics
Radius	-
Absolute magnitude (V)	-
Notable features	-
Other designations	Hubble's Variable Nebula,[1] Caldwell 46
See also: Diffuse nebula, Lists of nebulae
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NGC 2261 (also known as Hubble's Variable Nebula or Caldwell 46) is a variable nebula located in the constellation Monoceros. It is illuminated by the star R Monocerotis (R Mon), which is not directly visible itself.

NGC 2261 was imaged as Palomar Observatory's Hale Telescope's first light by Edwin Hubble on January 26, 1949,^[2] some 20 years after the Palomar Observatory project began in 1928. Hubble had studied the nebula previously at Yerkes and Mt. Wilson.^[2]

One explanation proposed for the variability is that dense clouds of dust near R Mon periodically block the illumination from the star.^[3]

See also

• NGC 1555
• New General Catalogue

References

1. ^ ^{a b c} "SIMBAD Astronomical Database". Results for NGC 2261. http://simbad.u-strasbg.fr/Simbad. Retrieved 2007-04-11. 
2. ^ ^{a b} http://365daysofastronomy.org/2009/01/26/january-26-60th-anniversary-of-hale-telescope-first-light/
3. ^ "A model for the cometary nebula NGC 2261". SAO/NASA ADS Astronomy Abstract Service. http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1978ApJ...226..455A. Retrieved 2010-11-28. 

External links

• European Homepage for the HST – Hubble photos and information on NGC 2261
• wikispaces.com – Images by amateur astronomers
• NGC 2261 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images