Space Physics

Question 1

1) What’s within our solar system? (2)

How did our solar system come to be?

Answer 1

1) Within our solar system there is one star, the Sun, plus the eight planets and the dwarf planets that orbit around the Sun. Natural satellites, the moon that orbit planets, are also part of the solar system.
- Our solar system is a small part of the Milky Way galaxy.

2) The solar system formed from gas and dust clouds that gradually become more and more concentrated because of gravitational attraction

Question 2

How are stars initially formed? (3)

Answer 2

• Stars and dust initially formed from a cloud of dust and gas called nebula.
• The force of gravity pulls the dust and gas together to become more concentrated and form a protostar. The temperature rises as the protostar get denser and more particles collide with each other. This process transfers energy from the GPE store of the protostar to the thermal energy store
• When the temp gets high enough, hydrogen nuclei undergo nuclear fusion to form helium nuclei- this gives out huge amounts of energy which keeps the core of the star hot. A star is born.

Question 3

How is the main sequence star formed?

Why do stars such as the sun radiate energy?

Answer 3

• Star enters a long stable period where the outward pressured caused by the nuclear fusion that tries to expand the star balances the force of gravity, pulling everything inwards. In this stable period, it’s called the main sequence star and lasts several billion years. THE FORCE OF GRAVITY AND THE RADIATION PRESSURE ARE IN BALANCE.
• Stars such as the sun radiate energy because of hydrogen fusion in the core and hence they are called main sequence stars because this is the main stage in the life of a sta

Question 4

Why is the sun a ‘stable star’?

Answer 4

• Sun is stable because gravitational forces acting inwards balance the forces of nuclear fusion energy in the core acting outwards.

Question 5

What happens to the main sequence star eventually? (2)

Answer 5

• Eventually, the hydrogen begins to run out in its core and the star the swells into a red giant if it is a small star or a super red giant if it’s a larger star( stars that are much bigger than the Sun)- it becomes red because the surface cools.
• Fusion of helium and other light elements in the core fuse together to form heavier elements( up to iron) are created in the core of the star

Question 6

What are the two things that happens after a red giant?

Answer 6

• When there is no more light elements in the core, fusion stops and no more radiation is released because the star becomes unstable-> star ejects its outer layer of dust and gas and because of its own gravity, star collapses upon itself and turns from red, yellow, to white and forms a white dwarf which will gradually cool and fade away into a black dwarf.

Question 7

What happens to stars much bigger than the Suns at the end of their lives after the main sequence stage? (2)

Answer 7

• 1) Big stars glow brightly again as they undergo more fusion and expand and contract several times, forming elements as heavier as iron in various nuclear reactions
• These stars swell out to become red supergiants and they then collapse- the matter surrounding the star’s core compresses and more and more this compresses causes t

them to explode in a supernova, forming elements heavier than iron and ejecting them into the universe to form new planets and stars; stars and life cycles produce and distribute all naturally occurring elements

Question 8

What does the exploding supernova do? (2)

Answer 8

-Exploding supernova throws outer layers of dust and gas into space, leaving a v dense core = neutron star.
-If the star is massive enough, it will become a black hole
and the gravitational field of a black hold is so strong and super dense point in space that not even light can escape from

Question 9

What is a supernova?

Answer 9

-explosion of a red giant where the core collapses on itself.

Question 10

Outline the life cycle of stars. (3)

Answer 10

1) Cloud of dust and gas-> Protostar-> Main Sequence star-> Stars much bigger than Sun( Red Super Giant) or stars about the same size as the sun (red giant)
2) Red Super Giant-> Supernova-> Neutron Star or Black Hole.
3) Red Giant-> White or Black Dwarf

Question 11

What is within our solar system? (4)

Answer 11

1) Planets- large objects that orbit a star- 8 of them0 Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune and their gravity is strong enough to have pulled in any nearby objects apart from their natural satellites.
2) Dwarf planets(pluto)- planet like objects that orbit stars.
3) Moon- natural satellites- thes orbit planets.
4) Artificial satellites- generally satellites that humans have built and they orbit the Earth

Question 12

Define milky way galaxies?

Answer 12

A massive collection of billions of stars that are held together by gravity.

Question 13

Define a satellite?

Answer 13

• an object that orbits a second, more massive object

Question 14

What causes the planets to move around the Sun?(4)

Answer 14

• gravity provides the force which creates orbits and the planets move around the Sun in almost circular orbits.
• the force of gravity on the planet from the Sun act towards the centre of the Sun and this is the resultant force because no other forces act on it and this is an example of a centripetal force because it acts towards the centre of the circle.
• if an object is travelling in a circle, it is constantly changing direction which means it is constantly accelerating and the direction of the motion of any planet in a circular orbit is at right angles to the direction of the force of gravity on it- the force of gravity can lead to a change in velocity but unchanged speed- CIRCULAR MOTION
• the object keeps accelerating towards what its orbiting but the instantaneous velocity (which is at right angles to the acceleration) keeps it travelling in a circle - the force that makes this happen is provided by gravity between the planet and the sun or between the planet and its satellites..
• for a stable orbit, the radius must change if the speed changes

Question 15

What does the size of the orbit depend upon on?

Answer 15

1) the closer you ge tto the planet, the stronger the gravitational force is and the stronger the force, the faster the orbitting objet needs to travel in order to remain in orbit.
- for an object in a stable orbit,, if the speed of the orbit changes, the radius of its orbit must do so too and faster moving objects will move in a more stable orbit with a smaller radius than slower moving ones.

therefore to stay in orbit at a particular distance, a small body must move at a particular speed around a larger boy

Question 16

What evidence is there that galaxies are moving away from each other?

Answer 16

-There is an observed increase in the wavelength of light from most distant galaxies. The further away the galaxies, the faster they are moving and the bigger the observed increase in wavelength. This effect is called red-shift.

Question 17

Explore the concept of red shift. (3)

Answer 17

• It is called the red shift between the wavelengths are sifted towards the red end of the spectrum and this suggest that the source of light is moving away from us(receding) and it’s the same result in whichever direction.
• more distant galaxies have greater red shifts than nearer ones and this means that they are moving away faster than nearer ones
• if the star or galaxy is moving towards you, the wl of waves is reduced and this called the blue shifts because the spectrum of light is shifted towards the blue part of the spectrum

Question 18

What do the dark spectral lines show?

The bigger the shift?

Answer 18

• are caused by the absorption of light by specific atoms such as hydrogen that make up a star or galaxy and the position tells you if there is a shift and if this shit is a red shift or a blue shift.

The faster a star or galaxy is moving( relative to you) the bigger the shift is

Question 19

How is the idea of a Big Bang supported and define briefly what theory it is?(2)

Answer 19

• The observed red-shift provides evidence that space itself (the universe) is expanding and supports the Big Bang theory.
• The Big Bang theory suggests that the universe began from a very small region that was extremely hot and dense and then it ‘exploded’- space started expanding and hence expansion is still going on

Question 20

How can new evidence change our theories? (3)

Answer 20

Since 1998 onwards, observations of supernovae suggest that distant galaxies are receding ever faster.

• currently, scientiss think that that universe is mostly made up of dark matter and dark energy.
• Dark matter is the name given to unknown substances which hold galaxies together but does not emit any electromagnetic radiation
• Dark energy is thought to be responsible for the accelerating expansion of the universe- lots of different theories about it but these theories get tested over time and our accepts or rejected

Question 21

How does blowing a balloon covered in pompons explain the red shift?

Answer 21

• as you blow into the balloon, it stretches and the pompons move further away from each other and the ballon represent the universe and each pompon is a galaxy- so as time goes on, space stretches and expand, moving the galaxies away from each other but shows how the expansion of space makes it look like galaxies are moving away from each us

Question 22

How does Hubble’s work provide major evidence for the Big Bang?

Answer 22

-Hubble saw wavelengths of dar light were longer than expected and this phenomena is called the red shift as wl of the colour red are longest in this spectrum and red shift is defines as the stretching of the wavelength towards the red end of the spectrum and he found that the furhter away the galaxies were from us, the further their light was red shifted- they were travelling faster away from us and the speed was proportional to the distance away, strongly suggesting that all the galaxies would have originated from a single point some time in the finite past and this was the first major evidence for Big Bang Theory.

Question 23

Explain why an acceleration of a planet in circular orbit changes the planet’s velocity but not its speed? ( 6 marks)

Answer 23

(1) The acceleration acts along the radius of the orbit towards the centre. This means that it is right angles to the planet’s speed( instantaneous velocity) and causes the planet to move on a circular path.
(1) Accel that is perpendic to the directio of motion does not affect the speed of the motion, it just changes the direction therfore speed of planet is not changed by the acceleration.
(1) Velocity is a vector quantity with magnitude and direction.
(1) The planet’s veloc is constantly changing because its direction is constantly changing hence circular motion means the the object experiences changing velocity but not changing speed.