The California Nebula ( NGC 1499/ Sh2-220) is an

emission nebula An emission nebula is a nebula formed of ionized gases that emit light of various wavelengths. The most common source of ionization is high-energy ultraviolet photons emitted from a nearby hot star. Among the several different types of emissio ...

located in the constellation

Perseus In Greek mythology, Perseus (Help:IPA/English, /ˈpɜːrsiəs, -sjuːs/; Greek language, Greek: Περσεύς, Romanization of Greek, translit. Perseús) is the legendary founder of Mycenae and of the Perseid dynasty. He was, alongside Cadmus ...

. Its name comes from its resemblance to the outline of the US State of

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

in long exposure photographs. It is almost 2.5° long on the sky and, because of its very low

surface brightness In astronomy, surface brightness (SB) quantifies the apparent brightness or flux density per unit angular area of a spatially extended object such as a galaxy or nebula, or of the night sky background. An object's surface brightness depends on its ...

, it is extremely difficult to observe visually. It can be observed with a H''α'' 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 A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. Originally meaning only an optical instrument using lenses, curved mirrors, or a combination of both to observe ...

under dark skies. It lies at a distance of about 1,000

light year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...

s from

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

. Its fluorescence is due to excitation of the H''β'' line in the nebula by the nearby prodigiously energetic O7 star,

Xi Persei Xi Persei (ξ Persei, abbreviated Xi Per, ξ Per), known also as Menkib , is a star in the constellation of Perseus (constellation), Perseus. Based upon stellar parallax, parallax measurements taken during the Hipparcos mission, it is app ...

(also known as Menkib). Menkhib and the California Nebula

The California Nebula was discovered by

E. E. Barnard Edward Emerson Barnard (December 16, 1857 – February 6, 1923) was an American astronomer. He was commonly known as E. E. Barnard, and was recognized as a gifted observational astronomer. He is best known for his discovery of the high proper mo ...

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.

References

External links

NGC 1499 at SEDSMenkhib and the California Nebula
by the

Wide-field Infrared Survey Explorer Wide-field Infrared Survey Explorer (WISE, observatory code C51, Explorer 92 and SMEX-6) is a NASA infrared astronomy space telescope in the Explorers Program. It was launched in December 2009, and placed in hibernation mode in February 2011, ...

(WISE) {{DEFAULTSORT:California Nebula NGC objects Perseus (constellation) Emission nebulae Sharpless objects ?