is a cloud of dust and gas, composed primarily of hydrogen
(97%) and helium (3%). Within a nebula, there are varying regions
when gravity causes this dust and gas
just know that nebulae (plural for nebula) are the birth place
of stars. The Hubble Space Telescope has increased our knowledge
about this with some great photos from space which clearly
show stars in different stages of development within a nebula.
from NASA - Protostar in the Eagle Nebula
to “clump” together. As these “clumps” gather more atoms (mass),
their gravitational attraction to other atoms increases, pulling
more atoms into the “clump.”
What causes these “gravitational
centers” to form in these huge clouds?
If you knew that, you’d have a Nobel Prize!
Adding atoms to the center of a protostar is a process astronomers
call accretion. Because numerous
reactions occur within the mass of forming star material, a protostar
is not very stable.
In order to achieve life as a star, the protostar will need to
achieve and maintain equilibrium.
What is equilibrium? It is a balance, in this case a balance between
gravity pulling atoms toward the center and gas pressure pushing
heat and light away from the center. Achieving and keeping this
balance is tough to do. When a star can no longer maintain equilibrium,