When Romans referred to the word "nebula" they were speaking of clouds.
That is probably why a lot of things that are not truly nebulas were
classified as nebulas, such as star clusters or galaxies. Nebulae are
interstellar gas and dust clouds, rather than groups of stars, which should
be labeled as constellations instead. Nebulae form many different shapes.
There are plenty of types of nebulae, such as emission nebulae, dark nebulae,
planetary nebulae and reflection nebulae.
When protons decide to join with electrons to produce hydrogen atoms,
light emits from an emission nebula. The energy produced from the electrons
moving into the protons produces a lot of light. At some point a photon of
red light escapes from the electron. The emission nebula is red because of
the large amount of active electrons. These clouds are full of gas at
extremely high temperatures. If you wish to travel there, you might find it
a little to easy to burn food. Emission nebulae are formed through
ionization. Ionization is the process in which electrons are stripped away
from atoms. When a very hot star produces ultraviolet light with lots of
energy that shines onto a hydrogen gas cloud, it creates an emission nebula.
After a neighboring star energizes the atoms hidden inside of the crazy
cloud, it falls back to lower levels of energy by dispersing radiation.
Emission nebulae are the sights you see when a star is born.
Dark nebulae are mainly composed of dust that blocks light. They go hand
in hand with reflection nebulae, which are blue dust clouds that reflect
light from neighboring stars. The size of the grains of dust enables blue
light to be reflected better than red light.
Toward the end of a star's life it sometimes throws out gas shells.
These shells of gas look like planets, henceforth their name, planetary
nebulae. Planetary nebulae are normally smaller than a light-year across.
It has been predicted that the Sun of our solar system will shed its own
planetary nebula in approximately five billion years. The death and
destruction of something somehow brings a new beginning always, as
demonstrated by these wonders of our universe.
