Birth of stars
Nebulas provide the gas and dust from which stars form, which starts with a slow accumulation of these materials. Gravitational attraction of clumps of dust/gas attracts even more material and it begins to contract, which raises the temperature. Once it reaches 15 million degrees Celcius in the center of the soon- to- be- star, fusion ignites! With the outward pressure of fusion, and inward pressure of gravity, it reaches equilibrium... Tada! Your small star is now born. |
Death of Stars
Main sequence: When the star runs out of energy (fusion then stops), gravity pushes in to the core and the outer layers expand (the star is now a red giant). The outer layer that expands right now is similar to dust; it doesn't stay long and it floats away with the solar wind. What's left after the 'dust' floats away is called a white dwarf. Later the white dwarf will turn into a black dwarf.
Intermediate Star: It's death is identical to the main sequence up until the red giant stage. At this stage fusion continues to happen; it produces heavy elements and if it doesn't lose a large amount of it's outer layer, gravity pushes inward in a second and causes a supernova. After this explosion all that remains is the collapsed core known as a neutron star, or pulsar. Or... the supernova continues to collapse in on itself and creates a black hole. |
Types of Stars
Main Sequence: Where the majority of the stars lay... consider it during the prime of their life.
Red Giant: Large in size, but cool in temperature. Also have a relatively small mass.
White Dwarf: About the size of the Moon, but with the mass of the Sun. Hot in temperature! (ex: A white dwarf the size of a book would have a mass of about 10,000 tonnes!)
Black Dwarf: The same as a white dwarf, but it's cooled down enough where it no longer emits light. (There are none as of yet, this takes tens to hundreds of billions of years for it to cool down entirely)
Supernova: A star becomes unstable to resist gravity and the core collapses, blowing the star apart.
Neutron Star/ Pulsar: The collapsed core after a supernova, higher density of even a white dwarf (ex: Weight of a supertanker/huge oil ship on a pinhead). They also rotate rapidly, emitting light similar to the way a light house does.
Black Holes: The result of a supernova collapsing in on itself.. it collapse so far that it compresses into itself.
|
Hertzsprung- Russell Diagram 
The Hertzsprung-Russell Diagram is use to classify stars according to their luminosity, spectral type, color, temperature and evolutionary stage. Stars in their stable phase ("prime of their life") are in the Main Sequence. Giants/ Super Giants are in the upper left corner, and the bottom left corner is for White Dwarfs.
Interesting tidbit: Did you know that stars are usually seen as pairs, triples, or even clusters? Lone stars like the Sun are in a minority!
Information used here are is from, A Guide to Skywatching, by David H. Levy. Image is from http://www.kheper.net/cosmos/stars/H-R.jpg . So it's not mine!
|
