Lives of Stars 8 th Grade Science

Lives of Stars 1. Stars begin as gas and dust called a nebula Gravity pulls the gas and dust in and fusion begins. This forms a Protostar or ‘new star’

Protostar

Lifetimes of Stars A star’s life depends on its mass. A star’s life depends on its mass. Stars smaller than the sun live up to 200 billion years. Stars smaller than the sun live up to 200 billion years. Medium sized stars like the sun live around 10 billion years. Medium sized stars like the sun live around 10 billion years. Stars 15 times more massive Stars 15 times more massive than the sun live about 10 million years.

Star Life Cycle 1. Nebula 2. Protostar 3. Main Sequence: 90% of stars. Hydrogen continues to burn and fuse to make helium. * Now the star can take 2 paths, depending on its size. Small/Medium Giant Stars Main Sequence

MAIN SEQUENCE

Small/Medium Size Stars Giant and Supergiant Stars Become red giants and then a planetary nebula. Can blow up into Supernovas. When a white dwarf runs out of energy, it turns into a black dwarf. The remains of a supernova become a neutron star or a black hole.

Planetary Nebula Planetary nebulae represent the final brief stage in the life of a medium-sized star like our sun. While consuming the last of the fuel in its core, the dying star expels a large portion of its outer envelope. This material then becomes heated by the radiation from the stellar remnant and radiates, producing glowing clouds of gas that can show complex structures, as the ejection of mass from the star is uneven in both time and direction. Explore a planetary nebula ry/tours/tour-catseye/

Small and Medium Stars These become giants and then These become giants and then Planetary Nebula – a shell of gas is ejected from the core of the star. Planetary Nebula – a shell of gas is ejected from the core of the star. White Dwarfs: blue-white core of a star that is left behind. White Dwarfs: blue-white core of a star that is left behind. These have no fuel, but glow faintly from left over energy. These have no fuel, but glow faintly from left over energy. When a white dwarf burns out, it is dead. Then it is a Black Dwarf. When a white dwarf burns out, it is dead. Then it is a Black Dwarf.

fusion WHITE DWARF The White Dwarfs are circled In the Hubble Space Telescope image below.

The life of Large Stars Giant/Super Giant: The star begins to run out of fuel. The star expands. Giant/Super Giant: The star begins to run out of fuel. The star expands. Supernova: Massive stars can blow up to an enormous size. Supernova: Massive stars can blow up to an enormous size.

Super Nova The explosion of a dying giant or supergiant star SUPERNOVAexplosion

Super Giants: When a Super Giant explodes into a supernova, it can become 2 things: When a Super Giant explodes into a supernova, it can become 2 things: 1. Neutron Star: Smaller and more dense than a white dwarf. They have 3 times as much mass as the sun, but are about the size of Houston! 2. Black Hole: This object is so dense, not even light can escape the gravity field. 2. Black Hole: This object is so dense, not even light can escape the gravity field.

Pulsar A neutron star that produces radio waves. Pulsars appear to pulse because they rotate!

Nebula  Protostar  Main Sequence Nebula  Protostar  Main Sequence Giant or Supergiant Giant or Supergiant White Dwarf Supernova White Dwarf Supernova Neutron Star Neutron Star Black Dwarf OR Black Dwarf OR Black Hole Black Hole

The life cycle of a low mass star (left oval) and a high mass star (right oval).

Binary Star Systems A star system with two stars. A star system with two stars. Stars that revolve around each other. Stars that revolve around each other. Sometimes this causes stars to appear as if they Sometimes this causes stars to appear as if they are blinking

Let’s Review! 1. All stars begin as gas and dust and is called a a. Protostar b. Nebula c. White dwarf d. Supernova

2. Most stars are in this stage a. Protostar b. White Dwarf c. Main Sequence d. Neutron Star

3. The life of a star depends on its a. Color b. Place in the universe c. Mass d. Temperature

4. If the star is super massive, it will live longer. a. True b. False

5. Low mass stars will become black holes a. True b. False

6. An object so dense, not even light can escape. a. Supernova b. Main Sequence c. Black Hole d. Nebula

7. A new star where fusion begins. a. Protostar b. Neutron Star c. Main Sequence d. Black Hole d. Black Hole

8. The most common chemical element in a star is A. Helium B. Hydrogen C. Carbon D. Sodium

9. The sun formed out of a A. Pulsar B. Supergiant star C. White Dwarf D. Nebula

10. Compared to Rigel, Alpha Centauri B is A. Cooler and brighter B. Cooler and dimmer C. Hotter and brighter D. Hotter and dimmer