Iris (NGC 7023) - November 2010



About the image …

Image Subject – NGC7023.
Location Taken – Teide Observatory (Canary Islands – Spain; 16º 30' 35" W, 28º 18' 00" N).
Telescope – IAC80 Telescope.
Instrument – CCD E2V 42-40.
Focal Ratio – Cassegrain f/11.3.
Exposure – R: 5 x 600s, V: 5 x 600 s, B: 5 x 600s.
Image Size – 2048 x 2048 pixels (10.4 x 10.4 arcminutes).
Image Type – RGB.
Software – DSS, PhotoShop CS4.
Images taken and reduced by – Daniel López.
Text – Daniel López and Pablo Rodríguez-Gil.

About the object...

Object Type – Reflection nebula.
J2000.0 Equatorial Coordinates – 21h 01m 35s; +68º 10’ 10".
Apparent Size – 18’ x 18’ (approx.).
Constellation – Cepheus.

The Iris Nebula (NGC 7023) is a reflection nebula located in Cepheus. Its gaseous and dusty matter disperses the light from the massive central star. The difference between reflection and emission nebulae is that the latter get their gas ionised by the central star, so it emits. In reflection nebulae the dust surrounding the forming star produces scattering of the stellar light. That’s the reason for their bluish colour. Another well-known example is the Pleiades (April 2008 AIM).

NGC 7023 was discovered by Sir William Herschel in 1794. It is located at about 1400 light years from the Earth and has a diameter of about 6 light years. It is called the Iris Nebula because of its resemblance to the flower of the same name. This month’s AIM only shows the central part of the NGC 7023 nebular complex due to the 10.4 x 10.4 arcmin field of the IAC80 telescope.