Transcript Lifecycle of a Star

Jumpstart 9/9/11
• How long would you expect a massive
star to live in comparison to a low mass
star? Explain your answer.
Lifecycle
of a Star
/Act One/
The Life of a Small to
Medium Mass Star
Nebula-
cloud of gas & dust
Protostar
Small Protostar…
Brown Dwarf
Too small to create enough heat to start fusion
Main Sequence Star
The protostar gains enough mass to begin fusion.
All main sequence stars fuse hydrogen
Red Giant
Small to medium main sequence star runs out of
hydrogen & begins fusing helium
Planetary Nebula
A Red Giant completely stops fusing & the outer layers
of the star are driven away
White Dwarf
The left over core of a star.
A white dwarf may only be the size of Earth, but it has a
mass equal to ½ of the Sun.
Black Dwarf
A white dwarf cools off over trillions of years
until it no longer emits light
/Act Two/
The Life of a
High Mass Star
Nebula-
cloud of gas & dust
Protostar
Massive Main Sequence Star
Massive main sequence stars fuse hydrogen
much faster than small or medium stars
Red Supergiant
Massive main sequence star runs out of hydrogen & begins
fusing helium, carbon, oxygen, etc.
Supernova
Fusion stops. The star collapses & creates a huge explosion.
Neutron Star
Super dense core of a star left over after a supernova.
Only 5 to 15 MILES in diameter, but have a mass 1.5 – 2 times
that of the Sun.
Black Hole
Stars with masses of 25 to 50 times of the Sun
form black holes after a supernova.
The leftover core of the star is so dense that it causes gravitational collapse.
Quick Write
How is the life cycle of a star related to the
HR diagram? Explain your answer.