Transcript Life Cycle of Stars

Stage 1: Nebula – Latin for “cloud”
• Nebula – cloud of Hydrogen gas and
dust in space, the birthplace of stars
– Gas and dust begin to collide, then
contract and heat up due to gravity
Orion Constellation
Orion Nebula
Horsehead Nebula in Orion
Pleiades Cluster
Pleiades Nebula
Pleiades Nebula
Stage 2: Protostar
• Protostar – As a nebula contracts, a small star
is formed
– Hydrogen particles fuse together to make
Helium (nuclear fusion), a star’s “fuel.”
Drawing of a Protostar
Hubble image of a Protostar
Hubble image of a Protostar
Stage 3: Main Sequence Star
• When the force pushing outward (fusion)
and the force pulling inward (gravity) are
equal, the star joins the main sequence.
– Where 90% of stars spend their lives
Colors
• What makes stars different colors?
– Their temperature
• Which color is the hottest?
–
–
–
–
–
Blue
White
Yellow
Orange
Red
• Which color is
our sun?
What happens next depends on the star’s mass (size).
– Low and Medium mass stars:
Stage 4 – Red Giant (Beginning of the end)
• A star begins to die when it runs out of Hydrogen in the
core.
• When the H is depleted, the He starts to fuse, and becomes
Carbon and Oxygen. The core contracts, and the outer
layers expand.
• Red Giant – the star gets bigger and cools down
Stage 5 – Death of Star:
• Once a Red Giant gets too massive, it
collapses under its own gravity, and the
core gets denser and hotter.
– Planetary nebula – the outer layers get
farther from the core, making the force of
gravity weaker. Then they drift off into
space.
Hourglass Planetary Nebula
around a dying star
Dying Star – “The eye of God”
Stage 5 – Death of Star (cont.)
– White dwarf – Once the outer layers
have drifted away, all that is left is the
dead core (no fusion).
–It is small and very dense (1/2 the
mass of the sun, but only the size of
the Earth).
White dwarf compared to the Earth
Hubble image of a white dwarf
Death of Stars: Low and Medium Mass
Nebula
Protostar
Main Sequence Star
Red Giant
Planetary Nebula
White Dwarf
Life Cycle of the Sun
• Our sun is a medium sized, main sequence star.
• It is a middle-aged star that is yellow in color.
• It will eventually become a red giant, planetary
nebula, and a white dwarf.
– High Mass Stars:
Stage 4 – Supergiant (Beginning of the end)
• Supergiant – greater than 10 x’s size of the sun;
the core contracts, and the outer layers expand.
Supergiant compared to the sun
• Stage 5 – Death of Star:
– A supergiant fuses heavier elements (C, O, Mg, N)
and gets bigger until it gets to Fe (no more fusion).
– Supernova – The core collapses, then the rest of
the star collapses, sending a shockwave that
creates an explosion.
Supernova - Crab Nebula
• Neutron Star – the super dense dead
core of a supergiant
– It is small and super dense (mass greater than
the sun, but the size of a large city).
Neutron Star
• Black Hole – When the extremely dense core of
a supergiant collapses, the gravity is so strong
that not even light can escape.
Drawing of a Black Hole
Death of Stars: High Mass Stars
Nebula
Protostar
Main Sequence Star
Red Super Giant
Supernova
Neutron Star
Black Hole
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