NGC 2261

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NGC 2261
Reflection nebula
Hubble's Variable Nebula - NGC 2261.png
An image of NGC 2261 by the Hubble space telescope.
Credit: HST/NASA/JPL/Judy Schmidt .
Observation data: J2000.0 epoch
Subtype variable nebula
Right ascension 6h 39m 10s[1]
Declination +8° 45′[1]
Distance 2,500 ly
Apparent magnitude (V) 9.0
Apparent dimensions (V) 2′
Constellation Monoceros
Designations Hubble's Variable Nebula,[1] Caldwell 46
See also: Lists of nebulae

NGC 2261 (also known as Hubble's Variable Nebula or Caldwell 46) is a variable nebula located in the constellation Monoceros. The nebula 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]

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