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: One of the most stunning deep-sky objects is the Pleiades open star cluster in Taurus, a celestial gem which has been cited by Homer (Illiad, 750 BC; Odyssey, 720 BC), Hesiod (700 BC), various ancient Greek astronomers as well as several references in the Bible. The star cluster is based known for its seven brightest members, aptly named after the seven daughters of Atlas and Pleione, and, more specifically, Alcyone, Asterope, Electra, Maia, Merope, Taygeta and Celaeno. Extended exposures of this cluster yield magnificent swarms of (reflective) nebulosity around the various member stars with Merope and Maia perhaps stealing the show owing to the fact they are characterized with the most intense and expansive molecular clouds. It is believed that the 100 million year-old star cluster, centered around Alcyone, will partially disintegrate as a cluster in approximately 250 million years. The cluster is best observed using binoculars or rich-field refractors during fall and winter and represents a very easy naked-eye object with at least six member stars being visible. In contrast, the nebulae around Maia and Merope are both quite faint (as suggested by the use of 10-min exposures for the image below) and large (similar to the apparent diameter of the full moon).
Please click on the image below to display in higher resolution (1200 x 900)
The Seven Sisters
M45, Mel 22, Cr42
I 3 r
RA / Dec:
03h 46m 09s /
24° 07' 00"
Dec 10, 2007
21:45 - 02:30 UT+2
AP 1200GTO GEM
SBIG LRGB + IR-block