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 H
α line at 656 nm) or H
β filter (isolates the H
β 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 H
β line in the nebula by the nearby prodigiously energetic O7 star,
Xi Persei (also known as
Menkib, seen at center below it in the inset at right).
[2]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.
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