Download 15-3

15-3
The Lives of
Stars
Studying the Lives of Stars
• Astronomers must study stars at different
stages to study the lives of stars
A star is born
Stars are born in nebula (a vast cloud of gas and
dust)
2. Gravity pulls gas together
3. When nuclear fusion takes place a star is born
4. The youngest stars are called protostars
1.
Lifetimes of Stars
• How long a star lives depends on it’s
mass
• The more mass a star has the shorter it
will live
Red Giant Stars
• As the mass of a star’s core decreases, so does its
gravity
• The core is no longer able to maintain the stars small
size, so it expands into a red giant.
Deaths of Stars
• When a star runs out of fuel it turns into a
white dwarf, a neutron star, or a black hole.
• White dwarfs
• The core of a red giant star whose outer layers
have dissipated (spreads out)
• Size of earth, with same mass as our sun
• Turns into a black dwarf when fuel runs out
• Neutron Stars
• Left over from a supernova
• Supernovas are giant explosions from dying
stars
• Left over core is called a Neutron Star
• 20km across
•three times the mass of our sun
Death of Stars Continued
• Black Holes
• Leftover from a supernova
of a very massive star
• 5 times the mass of the
sun packed into a sphere
the size of a marble
• Gravity so strong nothing,
not even light, can escape
• Quasars are black holes
millions of light years
away that shine very
bright (galaxies with black
holes in the center)