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Life Cycle of Stars SECTION 26.3. How Stars Form  The space around stars contains gas and dust, some areas its spread thinly or packed densely  A nebula.

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Presentation on theme: "Life Cycle of Stars SECTION 26.3. How Stars Form  The space around stars contains gas and dust, some areas its spread thinly or packed densely  A nebula."— Presentation transcript:

1 Life Cycle of Stars SECTION 26.3

2 How Stars Form  The space around stars contains gas and dust, some areas its spread thinly or packed densely  A nebula is a large cloud of gas and dust spread out over a large volume of space.

3 How Stars Form (cont.)  Some nebulas are glowing clouds lit from within by bright stars. Or they are cold, dark clouds that block light.  Stars form in the densest region of nebula.

4 How Stars Form(cont.)  Stars are created by gravity, it pulls a nebula’s dust and gas into a denser cloud.  The nebula heats up as it contracts.  If that contracting cloud has enough mass then it forms a protostar. As the protostar contracts, its internal pressure and temperature continues to rise.

5 How Stars Form (cont.)  A star is formed when a contracting cloud of gas and dust becomes so dense and hot that nuclear fusion begins.  The pressure from fusion supports the star against the tremendous inward pull of gravity. The new energy source stabilizes the young star.

6 Adult Stars  Stars spend 90% of their lives on the main sequence.  A star’s mass determines the star’s place on the main sequence and how long it will stay there.

7 Adult Stars (cont.)  A stars mass is determined by the gas and dust available when the star forms. Ex: Larger the star, more energy it has.  The more energy it “burns” the faster it will die away.

8 Adult Stars (cont.)  Stars similar to the sun occupy the middle of the main sequence.  Small nebulas produce small, cool stars that live longer than larger stars. Did You Know: These smaller stars can last for 100 billion years?

9 The Death of a Star  The decreasing supply of fuel in a star’s core leads to a star’s death as a white dwarf, neutron star, or black hole.

10 Low- and Medium-Mass Stars  Planetary nebula- Glowing cloud of gas that surrounds a dying star.  Red giant → Planetary Nebula → White Dwarf → Black Dwarf

11 High-Mass Stars  Supernova- An explosion caused by gravity overcoming the lower pressure in a star. Brighter than an entire galaxy.  Red Supergiant → Supernova → Neutron star or Black hole

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13 High-Mass Stars (cont.)  As a supernova spews material into space, the core continues to collapse.  A neutron star is the dense remnant of a high-mass star that has exploded from a supernova.  Neutron stars are much smaller and denser than white dwarfs.

14 High-Mass Stars (cont.)  Pulsar- A spinning neutron star that appears to gives off strong pulses of radio waves.  Black Hole An object whose surface gravity is so great that even electromagnetic waves, traveling at the speed of light, can’t escape from it.


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