P8: Space Physics

Question 1

Name the 8 planets of our solar system in order

Answer 1

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune

Question 2

What is a galaxy and which galaxy are we a part of?

Answer 2

A galaxy is a large collection of dust, gas and stars held together by gravity
- The Milky Way Galaxy

Question 3

What do planets orbit around?

Answer 3

• planets orbit a star ( e.g the sun)

Question 4

what is a nebula

Answer 4

A cloud of dust and gas

Question 5

Give the first 3 stages of a star’s life

Answer 5

nebula: A cloud of dust and gas is pulled together by gravitational force forming a protostar
- protostar
- Main sequence star

Question 6

Describe the process of nuclear fusion during the protostar stage:

Answer 6

• As a protostar ages its temperature and density increases which causes more frequent collisions between nuclei.
• nuclear fusion occurs when temperature is high enough for hydrogen nuclei to collide and join to form helium nuclei releasing lots of energy from the star’s core.

Question 7

What is the stable period of a star’s life known as ?

Answer 7

Main Sequence Star

Question 8

Explain why a star remains stable (2)

Answer 8

• The force of gravity pulling the material inwards is balanced by the outward radiation pressure caused by the energy released due to nuclear fusion.
• The star is at equilibrium

Question 9

Describe the last 3 stages of a star like our sun’s life ( low mass stars)

Answer 9

red giant: when the hydrogen runs out, the pressure pushing outwards no longer balances gravity. The core of the star collapses under gravity and the outer layers expand to form a Red Giant
white dwarf: Once the red giant stops fusing helium to elements up to iron, the star contracts under gravity to become a white dwarf
black dwarf: the star then cools down and stops releasing any energy forming a black dwarf

Question 10

Describe the last 3 stages for stars more massive than our sun (high mass stars)

Answer 10

1. red super giant: when the hydrogen runs out, the pressure pushing outwards no longer balances gravity. The core of the star collapses under gravity and the outer layers expand to form a Red Super Giant with a large surface area
2. supernova: This occurs when the Red Super giant can no longer carry out nuclear fusion thus it explodes in a supernova. The temperature due to explosion allows for the formation of elements higher than iron
3. neutron star or black hole

Question 11

How are elements heavier than iron formed?

Answer 11

• fusion of other elements
• in a supernova
• the explosion of a high mass stars distributes the elements throughout the universe

Question 12

what is an orbit?

Answer 12

the elliptical path that one object in space takes around another object. It is caused by the gravitational attraction between two objects.

Question 13

Define natural and man-made satellites and give an example of each

Answer 13

artificial: put into orbit around an astronomical object by humans eg the international space station
natural: the moon

Question 14

What allows planets and satellites to maintain their orbit and in what direction does it act on earth

Answer 14

• Gravity is the centripetal force that allows astronomical objects to maintain their circular orbits
• gravity acts perpendicular to the earth’s velocity.

Question 15

Define velocity

Answer 15

Velocity is speed in a given direction
It is a vector quantity thus it is measured in both magnitude and direction

Question 16

Explain how for circular orbits how velocity of an object changes but not its speed

Answer 16

As the direction of the orbit is constantly changing leading to a change in velocity.

Question 17

Explain how ,for a stable orbit, the radius of the orbit must change if the speed changes

Answer 17

If the speed increases, the radius must decrease as the satellite needs a greater force of gravity to prevent it from losing its stable orbit

Question 18

Give the components of the electromagnetic spectrum of decreasing wavelength

Answer 18

Radio waves
Microwaves
Infrared radiation
Visible light
Ultraviolet radiation
X-rays
Gamma rays

Question 19

Describe the Doppler effect

Answer 19

• when a source of sound or light moves away from an object , the frequency decreases and the wavelength increases

Question 20

What effect does distance of a galaxy from earth have on how fast the galaxy is moving and on the observed wavelength of absorbed light

Answer 20

The further the distance of a galaxy from earth, the increase of the galaxy’s velocity and the bigger the observed increase in wavelength ( the red shift)

Question 21

What is red shift

Answer 21

an observed increase in the wavelength of light from distant galaxies

Question 22

What does the Big Bang theory suggest

Answer 22

the universe started from a very hot and dense region in space which then exploded

Question 23

Explain how red shift observation support the Big Bang theory of the formation of the universe

Answer 23

if all galaxies are moving apart as seen by red shift , then they must have been closer together before.
it must have begun from a single point that was hot and dense (the big bang theory)

Question 24

What did scientists observe to provide evidence that the universe is expanding at a ever faster rate ?

Answer 24

• they observed supernovae which suggested that galaxies are moving away at an ever faster rate

Question 25

What two ideas could explain the universe’s ever increasing rate of expansion?

Answer 25

• the existence of energy and mass that we can’t detect known as dark matter and dark energy
• these ideas are being developed by scientists and are not yet fully understood