clouds of DUST & GAS - gravity makes gas/dust spiral together = protostar
gravitational energy converted to heat energy = temp. rises
- when temp.'s high enough, hydrogen nuclei - nuclear fusion = helium nuclei = heat & light
long stable period - heat created = outward pressure to balance gravity pulling inwards -
millions of years - massive amounts of hydrogen = MAIN SEQUENCE STARS
eventually hydrogen = runs out - stars swells = RED GIANT (small star) - RED SUPER GIANT (big star)
small-medium star (like Sun) - becomes unstable & ejects outer layer of dust & gas as PLANETARY NEBULA
hot dense solid core = WHITE DWARF - cools down = BLACK DWARF - disappears
big stars - glows brightly again - fusion & expand/contract several times = heavy elements like iron in nuclear
reactions - explode in SUPERNOVA (=elements heavier than iron) - ejects to form new planets & stars
exploding supernova - throws outer layer of dust & gas - very dense core - NEUTRON STAR - star = big enough = BLACK HOLE
HALF-LIFE = AVERAGE TIME it takes for the NUMBER
OF NUCLEI in RADIOACTIVE ISOTOPE SAMPLE to HALVE
time it takes for count rate to halve
Nuclear Fission & Fusion
Nuclear Fission - Splitting Up - big nuclei
nuclear power station - nuclear reactors - uranium-235/plutonium-239
chain reaction = nuclei split up & release heat energy - heats water - steam turbine - generator