GCSE Physics > P16: Space > Flashcards

P16: Space Flashcards

(58 cards)

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1
Q

Compare planets and comets

A

Similarities: They both orbit other objects
Differences: Comets are smaller, Comets orbit planets whilst planets orbit the sun

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2
Q

Compare comets and asteroids

A

Similarity: Both composed of rock, both relatively small
Difference: Meteors are burning whilst comets are frozen, comets orbit planets whilst asteroids do not

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3
Q

Explain why a comet cannot be seen far away

A

You only see them when they return near the Sun because then they heat up so much that they emit light.

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4
Q

Describe the birth of a star

A
  • Clouds of dust and gas pulled together by the gravitational attraction
  • these clouds joined becoming more and more concentrated, forming a protostar
  • As the protostar becomes denser, it gets hotter and this energy causes lighter nuclei to join together. Energy is released from this fusion reaction so the protostar gets even hotter
  • Getting hotter and brighter, it starts to shine, giving birth to a star
  • The outward force from pressure and expanding hot gas is balanced by the force of the star’s gravity
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5
Q

What causes a star to become stable?

A

➢ The force of gravity acts inwards trying to make the star contract
➢ The outward force of radiation from the nuclear fusion in its core trying to make the star expand

These forces stay in equilibrium until most of the hydrogen nuclei in the core have been fused together to form helium nuclei.

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6
Q

What ate main sequence stars?

A

Stars that in the main stage of their life. Such stars can maintain energy output for millions of years until there are no more hydrogen nuclei to fuse together by energy released in the core

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7
Q

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

A

Protostar
Main sequence star
Red giant
White dwarf
Black dwarf

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8
Q

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

A

Protostar
Main sequence star
Red supergiant
Supernova
Black hole/ neutron star

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9
Q

Why do stars with lower masses remain main sequence stars for a longer period of time?

A

Stars with low masses remain in their main sequence for much longer, as their core is cooler than that of more massive stars.

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10
Q

What is the process by which energy is released from stars?

A

Nuclear fusion

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11
Q

Why is a star stable during the ‘main sequence’ period of its lifestyle?

A

The inwards force of gravity and outward force of radiation is at an equilibrium

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12
Q

What causes stars of low masses to move past their ‘main sequence phase?

A

However, eventually, after billions of years, they run low of hydrogen fuel in their core. Once hydrogen in the centre is converted into helium, the star can no longer generate the nuclear energy required to balance the inward pool of gravity. At this stage, they begin to move off the main sequence into the next phase of their lives.

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13
Q

How does any star form a main sequence star?

A
  • The cloud of gas and dust heats as it contract. When it is hot and dense but nuclear fusion has not yet started it is known as a protostar
  • Stars are formed from large clouds of gas and dust that collapse under their own gravity until they are dense enough for nuclear fusion to begin
  • The core of the star heats as it contracts, causing the material around the core to heat up until hydrogen fusion begins here.
  • When the protostar reaches a critical density, fusion begins and the star starts to shine.
    When the outward pressure from fusion balances the star’s gravity, it stabilises as a
    main sequence star.
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14
Q

How does a star with low mass pass through its ‘main sequence stage? (Full explanation)

A
  • When the star runs out of hydrogen, this is the end of its ‘main sequence’ and it begins to swell out. Core contraction continues until it is hot enough for helium to fuse into carbon and oxygen.
  • Stars the same size as our Sun (or smaller) swell out and cool down turning red. A red
    giant.
  • When fusion stops no more radiation is released and the star collapses in on itself, this forms a ‘ White Dwarf’. This is smaller than it was before. Eventually it becomes cold, forming a ‘Black Dwarf’
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15
Q

How does a more massive star move through its ‘main sequence’ stage? (Full explanation)

A
  1. When core hydrogen runs out, nuclear fusion stops and core collapse begins. As with a small star, this heats up a surrounding shell of hydrogen, and shell hydrogen burning begins
  2. When the core heats up further and core helium burning begins, the star expands into a red supergiant
  3. When core helium runs out, the core collapse process starts again. This time it heats until a heavier element is ignited in a shell and in the core. This cycle continues until the star is ready to implode/ collapse
  4. Finally the star collapses extremely rapidly, creating a massive shockwave that blows the core apart in an explosion called a supernova.
  5. The explosion compresses the core of the star into a neutron star. This is an extremely dense object made up only of neutrons.
  6. If the star is massive enough, it become a black hole instead of a neutron star. The gravitational field of a black hole is so strong that nothing can escape from it. Not even light, or any other form of electromagnetic radiation.
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16
Q

What is a neutron star?

A

An extremely dense object made up only of neutrons.

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17
Q

Describe a black hole?

A

The gravitational field of a black hole is so strong that nothing can escape from it. Not even light, or any other form of electromagnetic radiation.

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18
Q

Explain how the elements are formed in a star?

A

As the star heat up, the hydrogen nuclei fuse to form the helium element within the core of a protostar

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19
Q

Explain how atoms of very heavy elements such as gold were formed

A

Heavy elements are formed when a massive star collapses then explodes as a supernova. The enormous force of the collapse fuses small nuclei into nuclei bigger than iron nuclei. The explosion scatters the elements throughout the universe.

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20
Q

Explain how, and when, atoms of different elements may be distributed throughout the universe

A
  • As fusion ends, the star collapses under the force of gravity.
  • This force is reflected in a large explosion called a supernova that expands exponentially as the surrounding gravitational force decreases at the end of the life of a star.
  • This distributes elements around the universe as they can expand to cover a solar system.
  • Planets form from debris surrounding a new star. Because of this, these planets will be made up of all the known elements too.
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21
Q

What are the similarities between natural and artificial satellites?

A

Similarities:
Both orbit the earth
Both experience the same gravitational force produced by the earth

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22
Q

What are the differences between natural and artificial satellites?

A

Differences:
Frequently will take alternate paths
Different distances from earth
Satellites are artificial whilst the moon is natural

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23
Q

What is a satellite?

A

A satellite is anything that orbits a celestial body

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24
Q

What are the uses of satellites?

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A

Mapping(gps), weather, communication, space research, mobile data, to study phenomena such as black holes and quasars, maps of different planetary surfaces, study earth’s atmosphere, navigation, star maps

25
What is a geostationary satellite?
Geostationary satellites are satellites that stay above the same part of the earth at all times, meaning they will orbit the earth at the same rate that the earth rotation on its axis. It takes one day to complete one full orbit of the earth at approximately 36000km above the equator.
26
What are differences from a monitoring satellite and a geostationary satellite.
Alternatively, monitoring satellites will have a significantly lower orbit and orbit the earth every 2-3 hours.
27
Describe the path the moon takes around the earth
The moon takes a circular orbit however most other planets will follow an elliptical orbit.
28
Describe the path planets take around the sun
Objects orbit much larger bodies due to the force of gravity. The gravitational pull of the large body on the small object keeps it in orbit
29
What causes objects to orbit other bodies?
Objects orbit much larger bodies due to the force of gravity. The gravitational pull of the large body on the small object keeps it in orbit
30
If objects orbit due to gravitational pull, why don't they fall into the large body?
The force of gravity from the Sun pulls the Earth towards the centre of the Sun (centripetal force). The direction of the Earth's velocity is at right angles to the centripetal force.
31
What is centripetal force?
Centripetal force acts towards the centre of a circle. This force changes the direction of the planets velocity, therefore it continues to orbit the sun
32
What would happen to the planet if there was no centripetal force
The planet would continue in one direction and fly off into space, no longer orbiting the sun
33
What is the direction of a planets motion relative to force of gravity?
The direction of the planets motion is always at right angles to force of gravity exerted by the sun as the force is acting perpendicular to the direction of movement
34
Why is no work done on a planet in circular orbit?
In a perfectly circular orbit, the gravitational force does no work, because it always acts perpendicularly to the direction of the instantaneous velocity. To do work, the direction of force must be the same direction as movement.
35
What would happen if an object orbited the earth too slow?
Objects that are too close to the earth gradually lose speed due to atmospheric drag. The force of gravity would cause the object to accelerate toward the earth, changing the direction of motion and thus changing velocity, but not speed
36
What would happen if an object orbited the earth too fast?
It will continue to travel in its fixed path in a constant velocity and it will leave the earth's orbit
37
What happens if a satellite is further from the large body it is orbiting?
• The lower the particular speed is required to stay in a circular orbit. This is because the force of gravity on the satellite is lower. • The longer the satellite takes to move around one orbit as the circumference/distance the satellite must travel is greater.
38
What is the relationship between distance from large body and speed of satellite?
As average distance from the increases, the speed decreases as less is required to stay in orbit as they will experience less gravitational force from the earth
39
What is a theory?
An attempt to explain phenomena in our universe. Theories can’t actually be proven, but they can be disproven. If a theory is disproven then we look for another explanation. If a theory gains evidence that supports it then it becomes strongly accepted by most scientists as the dominant theory.
40
What is the Big Bang Theory?
The theory states that to begin with all the matter in the universe was concentrated into a single incredibly tiny point. This began to enlarge rapidly in a hot explosion (called the Big Bang). The Universe is still expanding today.
41
What is a strength of the balloon depiction of big bang theory?
It reflects how as the universe expands the galaxies become further from eachother
42
What is a weakness of the balloon depiction of big bang theory?
It suggests the universe has a bindery and that suggests that all galaxies are the same distance from the centre
43
What is the doppler effect?
● When a source moves toward an observer, the observed wavelength decreases and the frequency increases ● When a source moves away from an observer, the observed wavelength increases and the frequency decreases
44
What is an absorption spectrum?
If you pass light through a gas some wavelengths of light will be absorbed by the gas, forming an ‘absorption spectrum’.
45
What causes absorption lines on a spectrum?
Our Sun contains helium. We know this because there are black lines in the spectrum of the light from the Sun where helium has absorbed light. These lines form the absorption spectrum for helium.
46
How is red shift shown on a spectrum?
The absorption lines are shifted towards the red spectrum (red shift) relative to the absorption lines of the sun- suggests the star is moving away
47
How does speed of movement effect red shift?
The faster a light source moves the further its light will be ‘shifted’ and the further away it is
48
Explain how the spectrum 'shift' of absorption lines supports that the universe began from a very small point
- The absorption line moves towards the red end of the visible electromagnetic spectrum. - Therefore, it will have a greater wavelength,suggesting that the distant galaxy is moving away because as light reaches the galaxy, it is stretched according to the doppler effect. - This causing a greater wavelength whilst the frequency decreases. This results in a red shift, as the galaxy appears red
49
What is the difference between the 'Big Bang Theory' and the 'Steady State Theory'?
The big bang theory state sthe universe is being pushed outeard due to a large explotion beginning from an extremelly dense, hot small region whilst the steady state theory argues against this, stating matter and the universe has no origin as it has always existed.
50
What is Cosmic Microwave Background Radiation (CMBR)?
The Big Bang theory predicted the presence of ‘Cosmic Microwave Background Radiation’ (CMBR). The relatively uniform background radiation is the remains of energy created just after the Big Bang. This has been detected coming from every direction in space.
51
What do scientists believe to be the origin of CMBR?
Many scientists belive the origin of CMBR is the radiation produced shortly after the 'Big Bang'
52
Why was the discovery of CMBR so important to the scientists believing in the 'Big Bang' theory to be correct?
It suggests the universe is not static as it was once believed to be so and as it shows a uniform background radiation is still present- the remains of energy created just after the Big Bang., thus providing evidence for the Big Bang
53
How is the wavelength of CMBR likely to change over the next billion years and why?
The wavelength of CMBR is likely to increase as our galaxy would move further from the point of origin is the universe continues to expand, increasing red-shift
54
What does the future of the universe depend on?
The gravity from between galaxies could stop the expansion of the universe – possibly. This depends on the ‘mass’ of the galaxies and how much ’matter’ is between them and how much ‘space’ they take up. It depends on the density of the galaxies.
55
What is dark matter?
Astronomers know that because galaxies would spin much faster if their stars were the only matter in galaxies. The missing mass is thought to be dark matter (that can’t be seen). The presence of dark matter would mean the average density of the universe would be much bigger.
56
What are the two potential futures of the universe?
- The Big Yawn - The Big Crunch
57
What is the Big Yawn?
‘The Big Yawn’: If the density of the Universe is less than a particular amount then it will expand forever. Eventually the stars will die out and everything else with them.
58
What is the Bug Crunch?
‘The Big Crunch’: If the density is more than a particular amount then it will stop expanding and start contracting
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