One of Cepheus’s crown jewels,
NGC7023.
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The white pupil at the center of this reflection nebula’s blue iris is
HD200775, a young, Herbig Be-type star. The bright A2 blue-white star immediately below the nebula’s dust cloud is "HD 201731" in the
Henry Draper star catalog [1] and "HIP 104291" in the
Hipparcos star catalog [2]. The bright red orange star below the Iris Nebula is
T Cephei, a
Mira-type variable star, a red giant in the very late stages of its stellar evolution [3]. The
Ghost Nebula ("
Sh2-136" in the
Sharpless Catalog) is the faint yellow reflection nebula in the bottom of the image.
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[1] Henry Draper (1837–1882) was an American doctor and amateur astronomer who was a pioneer of astrophotography. He made the first photograph of the spectrum of a star (Vega) in 1872 and was the first to photograph the Orion Nebula in 1880. The star catalog that bears his name was published in sections by the Harvard Observatory from 1918-1924 and contained information on 225,300 stars extending down to magnitude 9m. Extensions of the catalog published in 1949 raised the number of stars included to 359,083. Its entries, however, are highly valuable and primarily in the form of finding charts which makes it practically unusable for modern computer-based astronomy.
[2] The
Hipparcos astronomic catalog compiles spectral data gathered by the European Space Agency's astrometric satellite
Hipparcos, which was operational from 1989 to 1993. It contains data on more than 118,200 stars.
[3] Mira-type stars pulsate at periods longer than 100 days with amplitudes greater than one magnitude in infrared and 2.5 magnitude at visual wavelengths.
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