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Bell Ringer – match term with definition
1. Large cloud of gas and dust
2. Longest stage
3. Hydrogen is depleted and outer layers expand and cool
4. Extremely dense
5. Light cannot escape
A. Black hole
B. Giant
C. Main sequence
D. Nebula
E. Neutron star
Nebula
• Cloud of gas and dust• 70% hydrogen, 28% helium, 2%
other elements• Weak gravitational attraction
NGC 604 – one of the largest regions of star birth currently known.
Contains massive stars, about 120 times larger than our sun.
Nebula to a star• Force (i.e. explosion from nearby star)
compresses particles• Nebula begins to contract• Particles come closer together• Temperatures increase• At 10 million K, nuclear fusion begins• Star is born
Nuclear Fusion
http://www.youtube.com/watch?v=-gRagBg7mjM&NR=1
Main sequence star
• Energy is generated in the core of the star• Hydrogen atoms fuse to helium
atoms• Longest stage in life of a star• Balances pressure from fusion
heat with gravity
Giants and Supergiants• Hydrogen fuel is used up• The core of the star contracts, increasing the
temperature• Outer shell of star expands and cools • Helium fuses to form carbon
• Giants are 10 times bigger than the sun. • Supergiants are 100 times bigger than the
sun.
Planetary Nebula
• Helium fusion ends• Star loses its outer gases• The core heats and illuminates
the ring of gas
Planetary Nebula – glowing shell of gas and plasma formed by some
stars when they die
White Dwarfs• Gravity pulls the last matter of
the star inward• Hot, dense core of matter• Shine for billions of years before they cool
completely into a black dwarf.
Nova
• During process of white dwarf cooling, explosions may occur
• Release energy, gas, and dust into space
• Star becomes much brighter and then fades back to its normal brightness
• May occur several times
Supernova• Occur in very large stars
• Large stars contract producing very high pressures and temperatures
• Carbon fuses into magnesium which then fuses into iron
• The iron core absorbs huge amounts of energy and collapses, causing the outer part of the star to explode
Neutron Stars
• The core of a supernova contracts into a very small, dense ball of neutrons
• Rotate very rapidly• Some emit beams of radiation
and are called pulsars
Pulsar - highly magnetized, rotating neutron stars that emit beams of
electromagnetic radiation
Crab Pulsar
Black Holes
• After a supernova,
some large stars
contract with even greater force
• The force crushes the core of the star, leaving a hole in space
• The gravity is so great that not even light can escape from it
Recycling
• Matter emitted by a star over its life time is recycled and can become part of a new nebula