topic 8 - space physics

Question 1

name the star found in our solar system

Answer 1

the sun

Question 2

name the 8 planets in the solar system

Answer 2

mercury, venus, earth, mars, jupiter, saturn, uranus, neptune

Question 3

State 4 other objects that orbit the sun

Answer 3

Dwarf planets, comets, asteroids, meteoroids

Question 4

Name two objects that orbit planets

Answer 4

the moon (natural satellites), man made satellites

Question 5

Why is Pluto considered a “dwarf planet”?

Answer 5

Pluto has not “cleared its neighbourhood” - its gravitational field strength is not “dominant” compared to other bodies in its vicinity in space

Question 6

How are stars formed?

Answer 6

• Stars form from clouds of dust and gas, these are called nebula - the main gas is hydrogen.
• In the first stage, Gravity causes the cloud of dust and gas to collapse.
• As the dust particles move faster, the temperature rises, which increases kinetic energy.
• Scientists call the collapsing cloud of hot gas and dust a protostar
• if the temperature of the protostar gets high enough then hydrogen nuclei join together to form helium -> this process is called nuclear fusion
• At this point the protostar has formed into a star

Question 7

what happens to stars that are the same size as our sun?

Answer 7

• At some stage, the hydrogen in the star begins to run out
• A this point, the outward force due to fusion energy is less than the inward force due to gravity
• this causes the star to collapse inwards
• the collapse of the star causes its temperature to increase
• Now helium nuclei fuse together to create heavier elements
• the star expands to form a red giant
• At some point, the red giant stops fusing helium
• At this stage, the red giant shrinks and forms a white dwarf
• Because the white dwarf is no longer carrying out fusion, it gradually cools down
  Eventually, it stops releasing any energy and it forms a black dwarf

Question 8

what happens to stars that are much bigger than the sun?

Answer 8

• The core of the star runs out of hydrogen
• The star expands and cools to form a Red Super Giant
• Nuclear fusion occurs to form heavier elements up to iron from lighter elements
• The outer layers of a red supergiant will then explode once there are no more elements to fuse as a supernova
• Elements heavier than iron are formed
• The core will then shrink to become a neutron star or a black hole if the mass of the star is large enough

Question 9

what is a neutron star?

Answer 9

a neutron star consists of neutrons densely packed together

Question 10

what is a black hole?

Answer 10

a black hole has such a large gravity that even light cannot escape

Question 11

For an object to maintain a stable orbit around the sun, what must happen to the radius of the orbit?

Answer 11

the radius of the orbit must decrease

Question 12

Name the centripetal force that allows planets and satellites to maintain their circular orbit

Answer 12

Gravitational force

Question 13

Explain how the different elements now contained in the Universe were formed

Answer 13

• nuclear fusion took place
• Hydrogen formed into helium
• Elements up to iron formed in the core of stars
• Elements heavier than iron are formed in the supernova.
• Heavy elements were scattered throughout the Universe by Supernova explosion

Question 14

Why does the velocity of the satellite change as it orbits the earth

Answer 14

• The velocity of the satellite changes as the direction is changing
• The object is changing as it is accelerating
• acceleration is caused by gravity

Question 15

What is the redshift?

Answer 15

The red shift is when the star or galaxy moves away from you and the wavelengths are stretched. It is called a redshift because the spectrum of light is shifted towards the red part of the spectrum

Question 16

What is the blue shift?

Answer 16

The blue shift is when the star or galaxy moves towards you because the light waves are compressed. This is called a blue shift because the light spectrum is shifted towards the blue part of the spectrum.

Question 17

What is meant by the Big Bang?

Answer 17

The Universe began from a very small region that was very hot and dense which then exploded

Question 18

What is meant by the steady state theory?

Answer 18

The galaxies are being pushed apart. They thought that this is caused by the matter entering the universe through “white holes”

Question 19

What is Big Yawn?

Answer 19

• If the density of the universe is less than a particular amount, it will expand forever. The stars will die out, and so will everything else

Question 20

What is Big Crunch?

Answer 20

If the density of the universe is more than a particular amount then it will stop expanding and go into reverse

Question 21

Explain how red-shift observations support the Big Bang theory.

Answer 21

• Galaxies show redshift which shows the galaxies are moving away
• The further galaxies are the bigger the redshift
• Means that the furthest galaxies are moving away the fastest
• So the universe is expanding
• Extrapolating backwards suggests that the universe starts from an initial certain point

Question 22

What type of objects can absorb and emit infrared radiation?

Answer 22

All objects

Question 23

What causes supernovae?

Answer 23

The red supergiant becomes unstable and its outer layers will explode