NGC 1990
| Emission nebula | |
|---|---|
| H II region | |
| reflection nebula | |
NGC 1990 around Alnilam
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| Observation data: J2000 epoch | |
| Right ascension | 05h 36m 16.2s |
| Declination | −01° 12′ 07″ |
NGC 1990 is a reflection nebula which is a molecular cloud of Epsilon Orionis. The stellar winds from Epsilon Orionis, or Alnilam, distribute the nebula approximately up to 2,000 km/s, more than 20 million times that of the stellar winds of the Sun.
NGC 1990 was discovered by William Herschel in 1786 with an 18.7 inch telescope. Herschel recorded the observation in his observing code as "!!!, eL, E, ε Orionis inv p" (Spectactular, extremely large, elliptical, epsilon Orionis preceding). However, there is doubt that this object exists in reality as several visual searches and modern astrophophy have failed to identify the exact location and extent of the reflection nebula. Modern photographs of the area with cameras show ultraviolet leak that gives the false impression of a large blue nebula around ε Ori (Alnilam). More careful photography does not reveal a nebula in the area.
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