- Dark Nebulae
: Dark nebulae are clouds of dust which are simply blocking the light
from whatever is behind. They are physically very similar to reflection
nebulae the difference in only because of the geometry of the light
source, the cloud and the Earth. Dark nebulae are also often seen in
conjunction with reflection and emission nebulae.
- Emission Nebulae :
Emission nebulae are clouds of high temperature gas. The atoms in the
cloud are energized by ultraviolet light from a nearby star and emit
radiation as they fall back into lower energy states. These nebulae
are usually red because the predominant emission line of hydrogen happens
to be red.
- Planetary Nebulae :
Planetary nebulae are shells of gas thrown out by some stars near the
end of their lives. Our Sun will probably produce a planetary nebula
in about 5 billion years. They often look a little like planets in small
telescopes.
- Reflection Nebulae :
Reflection nebulae are clouds of dust which are simply reflecting the
light of a nearby star or stars. Reflection nebulae are also usually
sites of star formation. They are usually blue because the scattering
is more efficient for blue light. Reflection nebulae and emission nebulae
are often seen together and are sometimes both referred to as diffuse
nebulae.
- Supernova Remnants :
Supernovae occur when a massive star ends its life in an amazing blaze
of glory. For a few days a supernova emits as much energy as a whole
galaxy. When it's all over, a large fraction of the star is blown into
space as a supernova remnant. |
