Photo By: Tony Hallas (CLICK photo for full size; all links below).

First observed by Sir William Herschel on October 18, 1794 (My brother’s birthday….just not the 1794 part) the Iris Nebula as it’s called; is a beautiful example of a reflection nebula. To be brief, a reflection nebula cannot illuminate itself, the illumination of gas and dust comes from the radiation provided by a nearby star. It happens to reside 1300 light years away in the constellation Cepheus.

The brightly glowing nebula is courtesy of the lonely newborn variable star SAO 19158 or HD 200775 which is about ten times the mass of our Sun. Not only is the star a newborn but it has a twin, though more like a Danny Diveto type twin (That isn’t an official catalog by the way) with an eccentric orbit and a periodicity of about 3.5 years. The star was born of this nebula and as it has now come to life the intense stellar winds (radiation) begin to blow the material away to get a look at the universe for the first time or to stick to the theme; opening its 6 light year in diameter petals to the universe. As we see it, the cavity blown open is about 5 x 2 light years in size.

The beautiful bluish color here is courtesy of atomic and molecular excitation and the refraction of light through the dust particles in the nebula. Also if you look closely you will see some red coloring in the nebula. This is due to a process called photoluminescence, where ultraviolet light gets converted into visible red light.

NAME: NGC 7023, Caldwell 4, Collinder 427, LBN 487, Iris Nebula.

WHAT IS IT?: Star Cluster in Reflection Nebula LBN 487 and centered on star variable star SAO19158 or HD200775.

HOW FAR AWAY IS IT?: Approximately 1300 light years distant.

HOW BIG IS IT?: The entire nebula is approximately 6 light years in diameter and 10’ X 08’ arcminutes on the night sky.

APPARENT MAGNITUDE?: Central star SAO 19158 is 6.8 which is just out of naked eye view but easily viewable with modest binoculars; the nebula itself is around 7.8.

WHERE IS IT? (General): Constellation Cepheus.

WHERE IS IT? (Exact RA/DEC J2000): RA 21h 01m 35.60s / +68° 10′ 10″

Tony & Daphne Hallas main website:

NASA APOD page for this photo:

NASA page on Polycyclic Aromatic Hydrocarbons (PHA’s):

SIMBAD data on star HD200775:

Image | This entry was posted in Astronomy (Learning), Astrophotography (DSOs), Images, Nebula (Emission, Reflection), Stars (Non-Sun Related) and tagged , , , , , , , , , , , , , . Bookmark the permalink.

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