Emission nebulas are large clouds of ionized plasma where star formation usually takes place. They are illuminated from within by groups of young stars that form in H II Regions within the nebula. |
Nebula Classification |
Composition Average Size Average Temp. Lifespan Color Example Pictured |
Hydrogen, helium, oxygen 100 - 5,000 ly 10 - 20 K 1 - 2 million years Red, green, blue Lagoon Nebula, Veil Nebula Krai’jih’na Nebula |
An H II region is a large stellar nursery, typically located inside an emission nebula. Over the duration of its lifespan, an H II region can give birth to thousands of stars. Gravimetric forces by the larger stars will eventually disperse the nebula and leave behind a star cluster similar to the Pleiades. |
Composition Average Size Average Temp. Lifespan Color Example Pictured |
Hydrogen, helium 20 - 2,000 ly 10,000 K 1 - 2 million years Red, pink Eagle Nebula Cone Nebula |
While an H II region can span light years and contain dozens of stars in varying states of development, Bok Globules are dense clusters of dust and gas where star formation actually takes place. They commonly result in binary and trinary star systems. |
Composition Average Size Average Temp. Lifespan Color Example Pictured |
Hydrogen, helium, carbon 1 ly 3 K 1 - 2 million years Black NGC 281, NGC 1999, BHR 71 IC 2499 |
Reflection nebulas are large clouds of dust that reflect light from nearby stars. The nearby stars are not usually hot enough to cause ionization, but are bright enough to make the dust visible. Star formation can occur within a reflection nebula. |
Composition Average Size Average Temp. Lifespan Color Example Pictured |
Hydrogen, carbon, iron, nickel 100 ly 25,000 K 10 million - 10 billion years Blue, purple Trifid Nebula, Witchhead Nebula Pleiades Cluster |
Despite the name, planetary nebulas have nothing to do with planets. They are, in fact, the final stage of life for most stars, developing when a star is no longer able to sustain nuclear fusion. As the star’s core contracts, it ejects ionized gases into space, creating a planetary nebula. This plays a crucial role in the evolution of the galaxy, for the process returns material to the interstellar medium. |
Composition Average Size Average Temp. Lifespan Color Example Pictured |
Carbon,oxygen,nitrogen,calcium 1 ly 10,000 K 10,000 years Orange, green, blue Ring Nebula, Hourglass Nebula Cat's Eye Nebula |
Dark nebulas are a type of large molecular cloud. The cloud cores are completely invisible to the naked eye, and are be undetectable aside from microwave emissions from the molecules within. Dark nebulas have strong magnetic fields that create considerable gravimetric forces in and around the nebula. Stars and astrophysical masers can form deep inside dark nebulas. |
Composition Average Size Average Temp. Lifespan Color Example Pictured |
Hydrogen 200 ly 7 K 1 - 2 million years Black Coalsack Nebula, Snake Nebula Horsehead Nebula |
When a massive star reaches the end of its life, it explodes in an immensely powerful supernova. This event blows the entire star apart, leaving in its wake a remnant nebula that expands into the interstellar medium. |
Composition Average Size Average Temp. Lifespan Color Example Pictured |
Ionized hydrogen, oxygen 3 ly 10,000,000 K 1,000,000 years Varies; typically orange, blue Tycho's Remnant,1987A Crab Nebula |
Nova remnants are similar to supernova remnants, only much smaller on all levels. They are also much more common. |
Composition Average Size Average Temp. Lifespan Color Example Pictured |
Ionized hydrogen, oxygen 0.5 ly 5,000 K 300 years Varies; typically blue, orange RR Pictoris T Pyxidis |
While most stars form within emission nebulas, there are exceptions to the rule. When a young star forms elsewhere, gravimetric forces gradually attract a disk of dust and gas that flatten to form a new star system that includes planets and asteroids. |
Composition Average Size Average Temp. Lifespan Color Example Pictured |
Hydrogen, helium, oxygen 100 AU 150 K 2,000,000 years Yellow, orange Panak A generic solar nebula |
A Wolf-Rayet nebula forms when strong stellar winds cause a Class O star to rapidly lose its mass. The dispersed mass forms a nebulous halo around the star. |
Composition Average Size Average Temp. Lifespan Color Example Pictured |
Helium, carbon, oxygen 0.5 ly 25,000 - 50,000 K 1 - 2 million years Blue NGC 6888, NGC 3199 Gamma Velorum |
Inversion nebulas are rare, highly unstable nebulas created by plasma strings. They typically burn out after a few years. |
Composition Average Size Average Temp. Lifespan Color Example Pictured |
Ionized plasma strings 200 AU 10,000 K 5 - 10 years Pink Lukkaris Nebula Marayna's Nebula |