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Lives of Stars. A star is born…  All stars begin their lives as NEBULAS, large clouds of gas and dust spread out in an immense volume.  A STAR, on the.

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Presentation on theme: "Lives of Stars. A star is born…  All stars begin their lives as NEBULAS, large clouds of gas and dust spread out in an immense volume.  A STAR, on the."— Presentation transcript:

1 Lives of Stars

2 A star is born…  All stars begin their lives as NEBULAS, large clouds of gas and dust spread out in an immense volume.  A STAR, on the other hand, is made up of a large amount of gas in a relatively small volume.

3 NEBULA

4 NEBULA

5 (continued)  In the densest part of the nebula, gravity pulls gas and dust together.  A cloud of gas that has enough mass to form a star is called a PROTOSTAR.  A star is finally born when the gas and dust from a nebula becomes so dense and hot that nuclear fusion starts.

6 PROTOSTAR

7 Lifetimes of stars…  How long a star lives depends on its mass.  Low mass stars (less mass than the sun): live for about 200 billion years.  Medium mass stars (same as sun): live for about 10 billion years.  High mass stars (15 times the mass of sun): live for about 10 million years.

8 Death of stars…  When a star begins to run out of fuel, its core SHRINKS and outer portion EXPANDS.  Depending on its mass it can become either a RED GIANT or SUPERGIANT.

9 RED GIANT

10 SUPERGIANT

11 (continued)  Low/Medium mass -----> Red giant  High mass > Supergiant  After a star runs out of fuel, it becomes a white dwarf, neutron star, or black hole.

12 White Dwarfs…  After a small/medium mass star runs out of fuel, its outer layers expand, and becomes a RED GIANT.  The outer parts keep growing until they form a glowing cloud of gas called a PLANETARY NEBULA.  The blue-white core of the star that is left is called a WHITE DWARF.  When a white dwarf stops glowing, it becomes a BLACK DWARF.

13 WHITE DWARF

14

15 PLANETARY NEBULA

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17 Supernovas…  After a high mass star runs out of fuel, its outer layers expand, and becomes a SUPERGIANT.  When a supergiant runs out of fuel, it can suddenly explode, and within hours the star blazes millions of times brighter.  The explosion is called a SUPERNOVA.

18 SUPERNOVA

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20 Neutron Stars…  After a supergiant explodes, some material is left behind.  NEUTRON STARS are the remains of high mass stars.  Smaller and denser than white dwrafs.  Some neutron stars spin; these are called PULSARS.

21 NEUTRON STAR

22 PULSAR

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24 Black Holes…  The most massive mass stars may become black holes.  BLACK HOLE= an object with gravity so strong that nothing (not even light) can escape.

25 BLACK HOLE

26 Diagram: Life of a small/ medium star…

27 Diagram: Life of a high mass star…


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