California Nebula

The California Nebula (NGC 1499/Sh2-220) is an emission nebula located in the constellation Perseus. Its name comes from its resemblance to the outline of the US State of California in long exposure photographs. It is almost 2.5° long on the sky and, because of its very low surface brightness, it is extremely difficult to observe visually. It can be observed with a Hα filter (isolates the Hα line at 656 nm) or Hβ filter (isolates the Hβ line at 486 nm) in a rich-field telescope under dark skies.[1] It lies at a distance of about 1,000 light years from Earth. Its fluorescence is due to excitation of the Hβ line in the nebula by the nearby prodigiously energetic O7 star, Xi Persei (also known as Menkib).[2]

Infrared image showing xi Persei's interaction with the nebula including a (red) shock wave in the gas and dust (upper left)
California Nebula
Emission nebula
Observation data: J2000.0 epoch
Right ascension04h 03m 18.00s
Declination+36° 25′ 18.0″
Distance1,000 ly
Apparent magnitude (V)6.0
Apparent dimensions (V)2.5° long
ConstellationPerseus
DesignationsNGC 1499, Sharpless 220

The California Nebula was discovered by E. E. Barnard in 1884.

By coincidence, the California Nebula transits in the zenith in central California as the latitude matches the declination of the object.

NASA selected the California Nebula as its Astronomy Picture of the Day on October, 22, 2022, based on a submission from an amateur astronomer taken from a ground-based telescope.[3]

References
  1. "The California Nebula". Observing at Skyhound. Retrieved December 23, 2013.
  2. "Menkib (Xi Persei)". David Darling. Encyclopedia of Science.
  3. "APOD: 2022 October 22 - NGC 1499: The California Nebula". apod.nasa.gov. Retrieved 2022-10-26.
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