Download 18.1 NOTES How are stars formed? Objective: Describe how stars

18.1 NOTES
How are stars formed?
Objective: Describe how stars form. Name some characteristics of stars
A star is a big ball of gases that gives
off heat and light. The Sun is only one
of billions of stars that make up are
galaxy, and there are billions of
galaxies. Most stars appear to be
white in color. However, there are
blue, white, yellow, orange, and red
stars. The color of a star determines
how hot in temperature it is. Stars
differ in size, brightness, and surface
temperature. How large and massive a star is determines what will eventually
happen to it.
Most stars are composed of hydrogen and helium. Hydrogen is the MOST
COMMON element in stars. Other elements include sodium, calcium, and iron.
A star forms from a cloud of gas called a
nebula. Gravity causes it to contract and
start spinning. The nebula flattens into a
disk. Material in the center of the disk
forms a protostar. The nebula continues to
contract until nuclear reactions begin,
allowing the protostar to give off light and
heat. A new star is born.
Most stars other than the Sun are
double stars. We call these stars
binary. Binary stars are pairs of
stars that travel through space
together and revolve around
each other.
Some stars contain three or more stars. They are called star clusters.
Some clusters are globular, or round in
shape.
Others are open, or loosely arranged.