NGC 7023
The Iris Nebula, in the constellation of Cepheus, is a reflection nebula that surrounds open cluster NGC 7023. The nebula is a complex mixture of reflection, emission and dark nebulosity surrounding a 7.4 magnitude star that illuminates the reflection nebula. The star, HD 200775, is a Herbig Be star that is a pre-main sequence star with a mass between 3 and 15 solar masses. The star is only 5,000 years old. The Iris Nebula is located 1,300 light-years away, and subtends an apparent angle of 15 x 12 arcminutes. At that distance, this would correspond to a true size of 5.6 light-years in diameter. The star cluster NGC 7023 shines at magnitude 7.1 and has a diameter of 5 arcminutes. NGC 7023 was discovered by William Herschel in 1794. North is to the right in the above image.
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