This document describes different stages and types of stars: - Main sequence stars like our Sun spend most of their lives fusing hydrogen into helium in their cores. - Red giants are large, reddish stars that have exhausted hydrogen fusion and begun fusing helium. - Planetary nebulae form when average-sized stars eject their outer layers after becoming red giants, leaving behind dense, hot cores called white dwarfs. - Brown dwarfs are failed stars too small to sustain nuclear fusion. - Variable stars change in brightness over timescales from seconds to years as they evolve. - Binary stars are two gravitationally bound stars that orbit a common center of mass.

2. • Is a point in a star’s
evolution during which
it maintains a stable
nuclear reaction.
• Stage during which a
star will spend most of
its life.
• Example:
• Sun

3. • Is a large star that is reddish or
orange in color
• Represents the late phase of
development in a star’s life
• When supplied Hydrogen has
been exhausted and Helium is
being fused.
• Causes the star to collapse,
raising temperature in the core.
• The outer surface of the star
expands and cools, giving it a
reddish color.

5. • Is the remnant of an
average-sized star that has
passed through the red
giant stage of its life after
the star has used up its
remaining fuel.
• At this point the star may
expel some of its matter
into space, creating a
planetary nebula .
• What remains is the dead
core of the star.

7. • Could also be called a failed
star
• Some protostars never
reach the critical mass
required to ignite the fires
of nuclear fusion
• If the protostar’s mass is
only about 1/10 that of the
sun, it will glow only briefly
until it energy dies out.

8. • Is a star that changes in
brightness
• Its fluctuations can
range from seconds to
years
• Stars usually change
their brightness when
they are young and
when they are old and
dying

9. • A system of two stars
that are gravitationally
bound to each other
• They orbit around a
common point– center
of mass
• Half of all the stars in
our galaxy are part of
the binary system