lives of stars. a star is born… all stars begin their lives as nebulas, large clouds of gas and...
TRANSCRIPT
Lives of Stars
A star is born…A star is born…
All stars begin their lives as NEBULAS, All stars begin their lives as NEBULAS, large clouds of gas and dust spread out in large clouds of gas and dust spread out in an immense volume.an immense volume.
A STAR, on the other hand, is made up of A STAR, on the other hand, is made up of a large amount of gas in a relatively small a large amount of gas in a relatively small volume. volume.
NEBULANEBULA
NEBULANEBULA
(continued)(continued)
In the densest part of the nebula, gravity In the densest part of the nebula, gravity pulls gas and dust together.pulls gas and dust together.
A cloud of gas that has enough mass to A cloud of gas that has enough mass to form a star is called a PROTOSTAR.form a star is called a PROTOSTAR.
A star is finally born when the gas and A star is finally born when the gas and dust from a nebula becomes so dense and dust from a nebula becomes so dense and hot that nuclear fusion starts.hot that nuclear fusion starts.
PROTOSTARPROTOSTAR
Lifetimes of stars…Lifetimes of stars…
How long a star lives depends on its mass.How long a star lives depends on its mass. Low mass stars (less mass than the sun): Low mass stars (less mass than the sun):
live for about 200 billion years.live for about 200 billion years. Medium mass stars (same as sun): live for Medium mass stars (same as sun): live for
about 10 billion years. about 10 billion years. High mass stars (15 times the mass of High mass stars (15 times the mass of
sun): live for about 10 million years.sun): live for about 10 million years.
Death of stars…Death of stars…
When a star begins to run out of fuel, its When a star begins to run out of fuel, its core SHRINKS and outer portion core SHRINKS and outer portion EXPANDS. EXPANDS.
Depending on its mass it can become Depending on its mass it can become either a RED GIANT or SUPERGIANT. either a RED GIANT or SUPERGIANT.
RED GIANTRED GIANT
SUPERGIANTSUPERGIANT
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Low/Medium mass -----> Red giantLow/Medium mass -----> Red giant High mass ------> SupergiantHigh mass ------> Supergiant After a star runs out of fuel, it becomes a After a star runs out of fuel, it becomes a
white dwarf, neutron star, or black hole.white dwarf, neutron star, or black hole.
White Dwarfs…White Dwarfs…
After a small/medium mass star runs out of fuel, After a small/medium mass star runs out of fuel, its outer layers expand, and becomes a RED its outer layers expand, and becomes a RED GIANT. GIANT.
The outer parts keep growing until they form a The outer parts keep growing until they form a glowing cloud of gas called a PLANETARY glowing cloud of gas called a PLANETARY NEBULA. NEBULA.
The blue-white core of the star that is left is The blue-white core of the star that is left is called a WHITE DWARF.called a WHITE DWARF.
When a white dwarf stops glowing, it becomes a When a white dwarf stops glowing, it becomes a BLACK DWARF.BLACK DWARF.
WHITE DWARFWHITE DWARF
PLANETARY PLANETARY NEBULANEBULA
Supernovas…Supernovas…
After a high mass star runs out of fuel, its After a high mass star runs out of fuel, its outer layers expand, and becomes a outer layers expand, and becomes a SUPERGIANT.SUPERGIANT.
When a supergiant runs out of fuel, it can When a supergiant runs out of fuel, it can suddenly explode, and within hours the suddenly explode, and within hours the star blazes millions of times brighter.star blazes millions of times brighter.
The explosion is called a SUPERNOVA. The explosion is called a SUPERNOVA.
SUPERNOVASUPERNOVA
Neutron Stars…Neutron Stars…
After a supergiant explodes, some After a supergiant explodes, some material is left behind. material is left behind.
NEUTRON STARS are the remains of NEUTRON STARS are the remains of high mass stars.high mass stars.
Smaller and denser than white dwrafs.Smaller and denser than white dwrafs. Some neutron stars spin; these are called Some neutron stars spin; these are called
PULSARS. PULSARS.
NEUTRON STARNEUTRON STAR
PULSARPULSAR
Black Holes…Black Holes…
The most massive mass stars may The most massive mass stars may become black holes.become black holes.
BLACK HOLE= an object with gravity so BLACK HOLE= an object with gravity so strong that nothing (not even light) can strong that nothing (not even light) can escape.escape.
BLACK HOLEBLACK HOLE
Diagram:Diagram:Life of a small/Life of a small/
medium medium star…star…
Diagram: Diagram: Life of a Life of a high high mass mass star… star…