Http:// Our Expanding Universe ESU06 - Stars Understands the role of gravity in forming and maintaining planets, stars,

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Our Expanding Universe

ESU06 - StarsUnderstands the role of gravity in forming and maintaining planets, stars, and the solar system

Learning Targets:

Knows the terms nuclear fusion, nova, supernova, black hole, neutron star, and nebula

Knows the basic structure and composition of a star

Knows the life cycle of a star



Stars – Facts • Can’t even estimate

how many there are• 100 Billion galaxies

each with 100 B stars

We can see ≈ 3000

People have always navigated by stars

Different stars do have different colors, brightness and sizes

Some stars are named



Stars – Facts

Some stars are binary stars and revolve around each other

binary means … … two



Stars – Facts

Constellation – a formation of stars that looks like a figure or design

Officially there

are …

… 88

technically Big Dipper is an asterism (not official)



Structure of a Star – Interior • Core – 15 Million degrees C

Made of gasses (H & He)

This is where fusion happens

• Convection Zone – Circulates hot gasses



Structure of a Star – Interior • Core – 15 Million degrees C

Made of gasses (H & He)

This is where fusion happens

• Convection Zone – Circulates hot gasses

1

2 3

4

5

6

8

7



Structure of a Star – Surface • Chromosphere – Bottom layer

of the surface 5500 degrees C

Prominence – gasses that kind of burp out of the sun

Solar Flare – gasses that blast out of the sun

• Corona – Next layer away from the core. 2 Million degrees C

What we see during eclipse

Sun spots – go along with Pr & SF coolerSolar Wind – sent out from flares, plasma, disrupts wx/electronics



Life Cycle of a Star - Birth• Large cloud of gas/ice/dust (nebula) • Also known as the “star nursery”

This material condenses (protostar) 1 million K

Fusion H He star 10 million K



Life Cycle of a Star - Life

At equilibrium stars are Main

Sequence Stars

equilibrium is reached

Gravity keeps pulling material in

Fusion, which releases energy, keeps pushing out

Stars spend most of their life as Main Sequence Stars



Life Cycle of a Star - Life• Star will last as

long as there is H to burn

• Higher the temperature of a star the brighter

• 90% of stars, including our sun, are main sequence stars



Review

1. What is the scientific word for a “star nursery”?

2. What material begins a star?

3. What happens to that material?

4. What is a “baby star” called?

5. What temperature is needed for it to become a star?



Review

6. Gravity pulls in, what pushes out?

7. What do we call it when the force pulling in matches the force pushing out?8. Where on the H-R diagram do stars spend most of their life?9. How long will a star last?

10. Is a bright star hotter or cooler?



Death - Average Size Star runs out of H no more pushing out

More stuff in – temp goes up Helium burns

Now it is a giant

He C

100 M K

Now becomes a white dwarf

(Dead)

Main Sequence Giant White Dwarf Nova

Novas (explosions of H & He) will appear from time

to time



Death - Large Size Same as with an average size star

Hydrogen (H) burns Helium (He) burns Carbon …Iron

Now it is a supergiant

He Fe

10 Billion Kelvin

More mass

ExplodesSupernova

Sends heavy

elements into

spaceNeutron

Star (Dead)

Main Sequence Supergiant Neutron Star



Death – Very Large Size

Now it is a supergiant

He Fe

100 B K

More mass

ExplodesSupernova

Sends heavy

elements into

spaceBlack Hole

Main Sequence Supergiant Black Hole

Same as with an average (and large) size starHydrogen (H) burns Helium (He) burns Carbon …Iron





Concept Map Nebula

Red Giant

Protostar

Supergiant

White Dwarf Supernova

Neutron Star

BlackHole

Average Lg/Very Lg

What gives birth to a star?

What do we call a “baby” star?

If it is an average size star what do we call it?

If it is a lg or very lg size star what do we call it?

What will it be when it dies?

What will happen when it burns through iron?

Large?Very Large

Novamay see

Documents

Http:// Our Expanding Universe ESU06 - Stars Understands the role of gravity in forming and maintaining planets, stars,