Good Afternoon!Good Afternoon!

Please get your eInstruction Please get your eInstruction remote and notebook.remote and notebook.

The sun is a medium sized star. The sun is a medium sized star. The sun is about 75% Hydrogen The sun is about 75% Hydrogen and 25% Helium. Where is the and 25% Helium. Where is the sun located on the H-R Diagram?sun located on the H-R Diagram?

A.A. White DwarfsWhite Dwarfs

B.B. Main SequenceMain Sequence

C.C. SupergiantsSupergiants

D.D. Red GiantsRed Giants

Lives of StarsLives of Stars

88thth Grade Science Grade Science

http://hubblesite.org/gallery/tours/

Left Column QuestionsLeft Column Questions

1.1. How do scientists classify stars?How do scientists classify stars?

2.2. What determines a stars lifetime?What determines a stars lifetime?

3.3. List the phases of the life cycle of a List the phases of the life cycle of a Sun-like star.Sun-like star.

4.4. List the phases of the life cycle of a List the phases of the life cycle of a Supergiant star.Supergiant star.

How do scientists classify stars?How do scientists classify stars? Size and massSize and mass

neutron stars, dwarfs, main neutron stars, dwarfs, main sequence, red giants, sequence, red giants, supergiantssupergiants

Temperature and colorTemperature and colorstar color is related to its star color is related to its surface temperaturesurface temperature

Brightness and luminosityBrightness and luminositystar luminosity depends on star luminosity depends on brightness and distance from brightness and distance from EarthEarth

Lifetimes of StarsLifetimes of StarsA star’s life depends on its A star’s life depends on its massmass

Stars smaller than the sun live up to Stars smaller than the sun live up to

200 billion years.200 billion years. Medium sized stars like the sun live Medium sized stars like the sun live

around 10 billion years.around 10 billion years. Stars 15 times more massive Stars 15 times more massive

than the sun live about 10 million than the sun live about 10 million years.years.

Life cycle of a Sun-like star nebula

protostar

main sequence

red giant

planetary nebula

white dwarf

Lives of StarsLives of Stars• Stars begin as gas and dust Stars begin as gas and dust

called a called a nebula.nebula. Helix Nebula Crab NebulaHelix Nebula Crab Nebula

http://hubblesite.org/gallery/tours/tour-helix/http://hubblesite.org/gallery/tours/tour-helix/

http://hubblesite.org/gallery/tours/tour-carina/http://hubblesite.org/gallery/tours/tour-carina/

Protostar

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

Main Sequence StarMain Sequence Star

Once nuclear fusion begins, a star is Once nuclear fusion begins, a star is in the main sequence stage of its life in the main sequence stage of its life cycle. cycle.

This is the longest and most stable This is the longest and most stable part of a star’s life.part of a star’s life.

Red GiantRed Giant

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

Small and Medium Small and Medium StarsStars

These become These become giantsgiants and then and thenPlanetary NebulaPlanetary Nebula – a shell of gas – a shell of gas

is ejected from the core of the is ejected from the core of the star.star.

White Dwarfs:White Dwarfs: blue-white core blue-white core of a star that is left behind.of a star that is left behind.• These have no fuel, but glow These have no fuel, but glow faintly from left over energy. faintly from left over energy.

When a white dwarf burns out, it When a white dwarf burns out, it is dead. Then it is a is dead. Then it is a Black Dwarf.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.

http://www.nasa.gov/mission_pages/hubble/science/ngc5189.html

Explore a planetary nebulahttp://hubblesite.org/gallery/tours/tour-catseye/

WHITE DWARF

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

Star Life CycleStar Life Cyclehttp://science.nasa.gov/astrophysics/focus-areas/how-do-stars-form-and-http://science.nasa.gov/astrophysics/focus-areas/how-do-stars-form-and-

evolve/evolve/

*A star can take 2 paths, *A star can take 2 paths, depending on its size or depending on its size or mass.mass.

Small/Medium

Size Star

Giant and Supergiant

Stars

Main Sequence

The life of Large The life of Large StarsStars

NebulaNebula ProtostarProtostar Main SequenceMain Sequence Super Giant:Super Giant: The star begins to run The star begins to run

out of fuel. The star cools and out of fuel. The star cools and expands.expands.

Supernova:Supernova: Massive stars can blow Massive stars can blow up to an enormous size.up to an enormous size.

Neutron Star/Pulsar Neutron Star/Pulsar or or Black HoleBlack Hole

Super NovaThe explosion of a dying giant or supergiant star

Kepler’s

Supernova

Remnant

http://hubblesite.org/gallery/album/query/supernova/

Super Giants:Super Giants: When a Super Giant explodes into a When a Super Giant explodes into a

supernova, it can become 2 things:supernova, it can become 2 things:

1. 1. Neutron Star:Neutron Star: Smaller and more Smaller and more dense than a white dwarf. They dense than a white dwarf. They have 3 times as much mass as the have 3 times as much mass as the sun, but are about the size of sun, but are about the size of Houston! Houston!

2.2. Black Hole: Black Hole: This object is so This object is so dense, not even light can escape dense, not even light can escape the gravity field. the gravity field. http://imagine.gsfc.nasa.gov/docs/science/know_l2/black_holes.html

PulsarPulsar

A neutron star that A neutron star that produces radio produces radio waves.waves.

Pulsars appear to Pulsars appear to pulse because they pulse because they rotate!rotate!

http://imagine.gsfc.nasa.gov/docs/science/know_l2/pulsars.html

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

star (right oval).star (right oval).

Binary Star Binary Star SystemsSystems

A star system with two A star system with two stars.stars.

Stars that revolve around Stars that revolve around each other. each other.

Sometimes this causes Sometimes this causes stars to appear as if they stars to appear as if they are blinkingare blinking

Let’s Review!Let’s Review!

1. All stars begin as gas and 1. All stars begin as gas and dust and is called a dust and is called a a. Protostara. Protostarb. Nebulab. Nebulac. White dwarfc. White dwarfd. Supernova d. Supernova

2. Most stars are in this 2. Most stars are in this stagestage

a. Protostara. Protostar

b. White Dwarfb. White Dwarf

c. Main Sequencec. Main Sequence

d. Neutron Stard. Neutron Star

3. The life of a star depends 3. The life of a star depends on itson its

a. Colora. Color

b. Place in the universeb. Place in the universe

c. Massc. Massd. Temperatured. Temperature

4. If the star is super 4. If the star is super massive, it will live massive, it will live longer.longer.

a. Truea. True

b. Falseb. False

5. Low mass stars will 5. Low mass stars will become black holesbecome black holes

a. Truea. True

b. Falseb. False

6. An object so dense, not 6. An object so dense, not even light can escape.even light can escape.

a. Supernovaa. Supernova

b. Main Sequenceb. Main Sequence

c. Black Holec. Black Hole

d. Nebulad. Nebula

7. A new star where fusion 7. A new star where fusion begins.begins.

a. Protostara. Protostar

b. Neutron Starb. Neutron Star

c. Main Sequencec. Main Sequence

d. Black Holed. Black Hole

8. The most common 8. The most common chemical element in a star ischemical element in a star is

A. HeliumA. Helium

B. HydrogenB. Hydrogen

C. CarbonC. Carbon

D. SodiumD. Sodium

9. The sun formed out of a 9. The sun formed out of a

A. PulsarA. Pulsar

B. Supergiant starB. Supergiant star

C. White DwarfC. White Dwarf

D. NebulaD. Nebula

10. Compared to Rigel, Alpha 10. Compared to Rigel, Alpha Centauri B isCentauri B is

A.A. Cooler and Cooler and brighterbrighter

B.B. Cooler and Cooler and dimmerdimmer

C.C. Hotter and Hotter and brighterbrighter

D.D. Hotter and Hotter and dimmerdimmer