Declination +8° 45′ Apparent dimensions (V) 2′ Constellation Monoceros | Right ascension 6 39 10 Distance 2,500 ly Magnitude 9 Apparent magnitude (V) 9 | |
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Similar NGC 2360, NGC 2362, NGC 2506, NGC 2419, NGC 2477 |
Ngc 2261 la cometina variabile
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, some 20 years after the Palomar Observatory project began in 1928. Hubble had studied the nebula previously at Yerkes and Mt. Wilson.

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



References
NGC 2261 Wikipedia(Text) CC BY-SA