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The sun is a medium sized star. The sun is about 75% Hydrogen and 25% Helium. Where is the sun located on the H-R Diagram? A. White Dwarfs B. Main Sequence C. Supergiants D. Red Giants

Lives of Stars 8 th Grade Science

Left Column Questions 1. How do scientists classify stars? 2. What determines a stars lifetime? 3. List the phases of the life cycle of a Sun-like star. 4. List the phases of the life cycle of a Supergiant star.

How do scientists classify stars? Size and mass Size and mass neutron stars, dwarfs, main sequence, red giants, supergiants Temperature and color Temperature and color star color is related to its surface temperature Brightness and luminosity Brightness and luminosity star luminosity depends on brightness and distance from Earth

Lifetimes of Stars 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.

Life cycle of a Sun-like star nebula protostar main sequence red giant planetary nebula white dwarf

Lives of Stars Stars begin as gas and dust called a nebula. Stars begin as gas and dust called a nebula. Helix Nebula Crab Nebula Helix Nebula Crab Nebula

Protostar Gravity pulls the gas and dust in and nuclear fusion begins. This forms a Protostar or ‘new star’.

Main Sequence Star Once nuclear fusion begins, a star is in the main sequence stage of its life cycle. Once nuclear fusion begins, a star is in the main sequence stage of its life cycle. This is the longest and most stable part of a star’s life. This is the longest and most stable part of a star’s life.

Red Giant The star begins to cool and the outer layers expand. The star begins to cool and the outer layers expand.

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.

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/

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

Star Life Cycle *A star can take 2 paths, depending on its size or mass. Small/Medium Size Star Giant and Supergiant Stars Main Sequence

The life of Large Stars Nebula Nebula Protostar Protostar Main Sequence Main Sequence Super Giant: The star begins to run out of fuel. The star cools and expands. Super Giant: The star begins to run out of fuel. The star cools and expands. Supernova: Massive stars can blow up to an enormous size. Supernova: Massive stars can blow up to an enormous size. Neutron Star/Pulsar or Black Hole Neutron Star/Pulsar or Black Hole

Super Nova The explosion of a dying giant or supergiant star Kepler’s Supernova Remnant

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!

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.

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