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

15. PLANETARY NEBULA

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

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

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…