Nebulae represent clouds of gas and dust which appear as hazy or fuzzy objects when viewed through a telescope and are
characterized as one of four types (emission, planetary, reflection or dark). Emission nebulae, such as the Lagoon
nebula (M8), simply glow, for example, with a stunning shade of red. Planetary nebulae appear as small greenish disks
through a telescope, thus emulating the planets Uranus and Neptune, as a result of gas masses being thrown off by dying
stars (ex. M27, Dumbbell nebula) or represent supernova remnants (ex. M1, Crab nebula). In contrast, reflection nebulae
are characterized with gas surrounding young stars which reflect the stellar light (ex. M45, Pleiades) and, thus, yield
beautiful images of nebulosity. Finally, dark nebulae are detectable and studied only using parts other than the visible
spectrum and are believed to be associated with the formation of stars (ex. M16 in Serpens).
Note: NGC 7822 along with Ced 214 to its immediate south represent a large and expansive region of emission nebulosity on the border between Cepheus and Cassiopeia. NGC 7822 represents a region of active star formation and includes the young open cluster Berkeley 59 at the western tip of the nebula with many of the member stars estimated to be only a few million years-old. NGC 7822 lies at a distance of 2,600 to 3,300 light-years away and spans approximately 30 light-years and 90 arc-minutes in diameter (equivalent to three full moons) and another 20 arc-minutes high. The nebula is believed to be illuminated by one of the brightest stars closest to the sun known, namely BD+66 1673, and whose surface temperature is approximately 45,000 degrees Kelvin.
Please click on the image below to display in higher resolution (1200 x 950)
Ced 215, Sh 2-171, CTB 2
RA / Dec:
00h 03m 36s /
68° 36' 36"
90' x 20'
Sept 16-17, 2010 (H-a, RGB)
21:05 - 03:30 UT+3
Sept 17-18, 2010 (RGB)
01:55 - 03:30 UT+3
AP 1200GTO GEM
Baader 7nm H-a
SBIG LRGB filters
2.65" per pixel