Physics: Space

What are the main parts of the solar system?

• 1 sun (star)

• 8 planets

• Moons - natural satellites which orbit planets

• Solar system is in the milky way galaxy (group of stars)

How do stars as massive as the sun form?

1. Nebula (Cloud of dust and gas, mainly hydrogen)

2. Gravity causes it to collapse

3. Causes the temp to increase

4. Forms a protostar

5. Hydrogen nuclei join to form helium - nuclear fusion (If hot enough)

6. Main sequence star

Why does a star stay balanced?

The force of gravity (inwards) and energy from nuclear fusion (outwards) balance each other.

Star is in equilibrium

What is the life cycle of stars the same size as the sun?

1. Nuclear fusion of hydrogen nuclei to form helium

2. Main sequence star is formed

3. Hydrogen begins to run out

4. Fusion force < Gravity, so the star collapse

5. Causes temp to increase

6. Helium nuclei fuse to create heavier elements

7. Star expands to make a red giant

8. Stops fusing helium, shrinks

9. Forms a white dwarf

10. Cools down (not doing fusion)

11. Forms a black dwarf

What is the life cycle of stars the larger than the sun?

1. Nuclear fusion of hydrogen nuclei to form helium

2. Main sequence star is formed

3. Hydrogen begins to run out

4. Expand into red super giants

5. Helium nuclei join to make heavier elements

6. Nuclear fusion stops

7. Star explodes (Supernova)

8. High temps allow elements heavier than iron be produced.

9. Can become a neutron star or Black hole

How are elements formed in stars?

Elements lighter than iron are formed when the helium nuclei joins in a main sequence star

Elements heavier than iron are formed in a supernove.

What is a black hole?

Has extremely large gravity

Even light can’t escape

What is a neutron star?

Has closely packed neutrons

What is circular orbit?

The earth orbits the sun in a circular orbit

It travels in a circle

What is an elliptical orbit?

Why do planets orbit the sun?

Gravity holds the planets in their orbit

What are artificial satellites?

NOT THE MOON

Man Made

Geostationary - orbit every 24 hours, face fixed point

Why does an orbit have a changing velocity?

• The acceleration of the satellite is constant

• Acceleration causes the direction to change

• Changing direction means the velocity changes because its a vector quantity.

What is the relationship between the speed and radius of an orbit?

Speed increases, Radius decreases

Inversely proportional

What is red-shift?

When the expected wavelength of light shifts towards the red end.

What does Red-Shift prove?

Galaxies further away are travelling faster

They have a longer wavelength, and are moving further away

The universe is expanding faster

The universe began from a small, hot, dense region

What is the Big Bang Theory?

The idea that the universe began from a small, hot, dense region

Which expanded

What confused scientist and what was their theory?

Assumed gravity would cause expansion of universe to gradually slow down

But rate of expansion is increasing

We don’t know why

Suggested that the universe contains Dark matter and dark energy which we can’t detect.

Which property of a star affects the wavelength?

Temperature

Increased temp, decreased wavelength.