Location of photoPommier Observatory, Portland, OR, U.S.A.
Date/Time of photo2011-09-01 through 2011-09-29.
EquipmentTelescope and Mount: Celestron Compustar C14 with Astrophysics 0.75x focal reducer (f/8.3). Camera:SBIG STL 11000M, Baader Planetarium LRGB filters.
Exposures: LRGB=360:35:35:35 minutes=7hours:45minutes total exposure.
DescriptionThe Iris Nebula (Caldwell 4) is a reflection nebula in Cepheus 1300 light-years from Earth. Within, we see a hot newborn star, HD2000775, of 10 solar masses emerging from a massive dust cloud. It's solar winds have cleared a surrounding bi-lobed zone measuring 5 x 2.5 light years. The surrounding dust scatters the star's visible light, just as our atmosphere scatters sunlight in the sky, rendering the nebula sky blue. In filaments above the star, dust is converting invisible ultraviolet light into visible red light by photoluminescence. 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.