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: Two very impressive and large areas of emission nebulosity in Cassiopeia are IC 1805
(Heart Nebula) and IC 1848 (Soul Nebula). IC 1805 represents an area of active star formation and which includes the open
cluster with the same designation at the center of the nebulosity and with a diameter of 20 arc-minutes and the smaller
open cluster Berkeley 65 to the southwest. Also prominent is the emission nebulosity
IC 1795 to the northeast and whose brightest section is catalogued
separately as NGC 896. The obscure galaxies Maffei I and Maffei II lie just beyond the southwest periphery. The nebula is
illuminated and sculpted by the young open cluster
Melotte 15 and which includes a sample of very hot young
stars which are characterized with a mass fifty times that of the Sun.
The Heart Nebula lies at a distance of about 6,500 light-years away and spans another 180 light-years in diameter.
Please click on the image below to display in higher resolution (1200 x 950)