The Iris Nebula (NGC 7023) in Cepheus

Posted by Rod Pommier
on Sunday, February 12, 2012

by Rod Pommier

Telescope and Mount: Celestron Compustar C14 Telescope/Mount. with 0.75x focal reducer (f/8). Camera:STL 11000M, Baader Planetarium LRGB filters. Dates: 2011-09-01 through 2011-09-29. Location: Pommier Observatory, Portland, OR, USA. Exposures: LRGB=360:35:35:35 minutes=7hours:45minutes total exposure.


The Iris Nebula (Caldwell 4) is a reflection nebula that lies 1300 light-years from Earth in the Constellation Cepheus. In it we can see a hot newborn star, HD2000775, which has 10 solar masses, emerging from a massive dust cloud. The star's solar winds have cleared a bi-lobed zone surrounding the star that measures 5 x 2.5 light years. The surrounding dust scatters the visible light from the star, just as our atmosphere scatters sunlight in the sky, rendering the nebula sky blue. In some filaments just above the star, the dust is converting invisible ultraviolet light into visible red light by photoluminesence. The blue nebula is surrounded by dark obscuring clouds of dust. While the Iris nebula is often referred to as NGC 7023, this is not strictly correct. NGC 7023 refers to the associated open star cluster to the west. The correct designation for the nebula itself is LBN 487.

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