not those types of stars! life cycle of stars what is a star? star = ball of plasma undergoing...
TRANSCRIPT
N O T T H O S E T Y P E S O F S TA R S !
LIFE CYCLE OF STARS
WHAT IS A STAR?
• Star = ball of plasma undergoing nuclear fusion.• Stars give off large
amounts of energy in the form of electromagnetic radiation. • An x-ray image of
the sun.
THE FIRST STEP!
• Stars are formed in a Nebula. • A Nebula is a very large cloud of gas and dust in space.
Orion Nebula
PROTOSTARS
• Dense areas of gas in the nebula collect due to gravity.• The dense areas of
gas take on a definite shape called protostars.
PROTOSTAR
• As gas is added, the pressure in its core increases.• Causing the gas molecules to move
faster, increasing friction.• Causing heat to be generated, increasing
core temperature leading to fusion.
NUCLEAR FUSION
• Nuclear Fusion: process by which two nuclei combine to form a heavier element.• New stars initially
will fuse hydrogen nuclei to form helium.
MAIN SEQUENCE STARS
• Results when protostar starts fusion• They fuse hydrogen to form helium, releasing enormous amounts of energy.• It takes about 10 billion years to consume all the hydrogen in a Main Sequence star.• The sun is a main sequence star!
RED GIANTS
• Collapsing outer layers cause core to heat up.• Fusion of helium into carbon begins.• Outer shell expands from 1 to at least 40
million miles across. ( 10 to 100 times larger than the Sun)• Red Giants last for about 100 million
years.
DYING A SLOW DEATH – MASS MATTERS
Red Giant
Mass < 3 x sun
White Dwarf
Black Dwarf
Mass > 3x sun
Red Super Giant
Super Nova
Neutron Star
Black Hole
WHITE DWARFS
• Fusion stops• The core is now very
dense and very hot. (A tablespoon full would weigh 5 tons!)• The core begins to
cool.• A white dwarf is
about 8,000 miles in diameter.
BLACK DWARFS
Eventually white dwarf cools to point where it emits no visible light
A black dwarf will continue to generate gravity and low energy transmissions (radio waves).
RED SUPER GIANTS
• If the mass of a star is 3 times sun or greater, the Red Giant will become a Red Supergiant.• Fuses carbon to iron.• The star will expand to be between 10 and
1000 times larger than our sun.
RED SUPER GIANTS
SUPERNOVA
• When a Supergiant fuses all of the Carbon into Iron, there is no more fuel left to consume.• The Core of the supergiant will then
collapse in less than a second, causing a massive explosion called a supernova.• A massive shockwave is produced that blows
away the outer layers of the star.• Supernova shine brighter then whole galaxies for
a few years.
SUPERNOVA
NEUTRON STAR
• Leftover core of super nova• If it has a mass of
less than 3 solar masses, then the core becomes a neutron star.
• 6 miles in diameter!
BLACK HOLES
• If the mass of the surviving core is greater than 3 solar masses, then a black hole forms.• A black hole is a core so dense and massive it will generate so much gravity that not even light can escape it.