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Physics > Topic 7: Astronomy > Flashcards

Topic 7: Astronomy Flashcards

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1
Q

What is the geocentric model?

A

The idea that Earth is in the centre of everything with the planets and the sun orbiting around it.

First proposed by the Greek astronomer Ptolemy.

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2
Q

What is the heliocentric model?

A

The idea that the sun is the centre of of the solar system with the planets including earth orbiting it.

First proposed by the polish astronomer Nicolaus Copernicus.

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3
Q

In the 16th century what was discovered and how did this support the heliocentric model?

A

The telescope was invested allowing people to see objects in space with much greater detail and to find new objects.

Galileo discovered four of Jupiter’s moons. By plotting their movements he proved nit everything orbited the Earth led him to support heliocentric theory.

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4
Q

What are comets?

A

Mostly made of ice and some can be seen with the naked eye by mostly seen using telescopes.

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5
Q

Where are most asteroid found?

A

In the asteroid belt between Mars and Jupiter. These are rocky bodies.

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6
Q

What is the current model of our solar system?

A

-8 planters
-5 Dwarf planets
-thousand of comets and millions of asteroids.
THESE ALL MOVE IN ELLIPTICAL ORBITS AROUND THE SUN.
-Many planets also have natural satellites (moons) orbiting around them.

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7
Q

What is a natural satellite.

A

A moon.

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8
Q

What are the order of the plants in our solar system?

A 
Mercury
Venus
Earth
Mars
Jupiter
Saturn 
Uranus 
Neptune

My Very Easy Method Just Speeds Up Naming

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9
Q

Why do telescopes orbiting around the Earth give much clearer images than ground based telescopes?

A

Clouds and dust in the air do not interfere with the image.

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10
Q

How do astronomers use photography and computers to study our universe and solar system?

A

Photography allows astronomers to make more detailed observations and measurements than making drawings.

Computers have further increased the speed and detail which information from telescopes can be analysed. Today photography enables astronomers to make detailed observations and computers are used for analysis.

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11
Q

What do we use to investigate our solar system?

A

Space probs,
Telescopes
And much more

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12
Q

How is radiation in our atmosphere studied?

A

Many objects in space emit radio waves and infrared radiation. Different types of telescopes are used to detect different types of electromagnetic waves. Some of these telescopes must be placed in orbit because the atmosphere absorbs some of the radiation they are designed to detect.

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13
Q

How are landers (that land in comets) designed?

A

They are fitted with:
-screws in the landing legs
-harpoons and a small thruster
This is in order to keep it on the surface. This doesn’t always work. Gravity on comets can be up to 1000x weaker than Earth.

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14
Q

What is the gravitational field strength on Earth?

A

9.81 N/kg

So the weight of 1kg mass is 9.81N

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15
Q

What does your weight depend on and what is the equation that links all of this together?

A

Depends on your mass and the gravitational field strength.

…..

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16
Q

What does the gravitational field strength on the surface of a body depend on?

A

Depends on the mass of the body and and the distance form it’s centre to its surface (radius). The greater it’s mass and the smaller it’s radius the greater it’s surface gravity.

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17
Q

What orbits to most bodies is our solar system have and how do they differ?

A

Most have an elliptical orbit. Planets have an almost circular orbit while comets have an highly elliptical orbit.

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18
Q

What are artificial satellites used for?

A

Communication and to observe the Earth and space.

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19
Q

How does the orbit of an artificial satellite differ?

A
  • highly elliptical orbits are used for communication in parts if the Earth near the poles.
  • satellites in a circular geostationary orbit (horizontal) remain over one point in the Earth and are used for broadcasting. These satellites move at 3070m/s.
  • low earth orbits need the least fuel for launching satellites. These move at 7500m/s,
  • a satellite in a polar orbit will eventually pass over all parts of the Earth.
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20
Q

Why does an orbiting body in an (almost) circular orbit always have a changing velocity?

A

It travels at a constant speed. However as it’s direction is constantly changing and velocity is a vector (magnitude and direction) it has a constantly changing velocity.

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21
Q

How does force change the direction of a satellite but not its speed?

A

A moving object will continue to move in a straight line unless there is a force acting on it to to make it change speed or direction. For a satellite in orbit, the gravitational force between the earths and it is at right angles to the direction of movement. So it changes direction not speed.

22
Q

For a satellite in a low orbit what must is do?

A

Gravitational forces on a satellite in a low orbit is greater than that on a satellite with a high orbit. The satellite in the low orbit has to be moving much faster to stay in orbit. It it slows down it will fall to Earth. It gains speed as it falls, until it is moving in a fast enough to stay in a new lower orbit. It it goes low enough to e counter contact with the atmosphere contact with the air will slow it down and it will eventually fall to Earth.

23
Q

What is a nebula?

A

A cloud of dust and gases (mainly hydrogen). These materials can be pulled together by their own gravity.

24
Q

How is a protostar formed?

A

As materials in the nebula pull together the cloud contracts to become denser. They hydrogen becomes hotter as it spirals inwards and May start to glow. As more mass is attracted the clouds gravitational pull gets stronger and heats the material even more.

25
Q

How does the main sequence of a star develop?

A

The temperature and pressure in the centre of the protostar become high enough to force hydrogen nuclei to fuse together to form helium (fission reaction). Fusion reactions release a lot of electromagnetic radiation. The star is now in the main sequence part of this life. Our sun is at this stage.

26
Q

How is the gravitational pull in star balanced?

A

Pressure from hot gases push out.

Gravity pulls star inwards.

27
Q

How does a red giant form?

A

When they have fused most of their hydrogen into helium, the core is nit hot enough to withstand gravity and it collapses. The outer layers expand to form a red giant, much larger than the original star.

28
Q

What fusion reactions happen inside of red giants?

A

The combing of helium nuclei to form heavier heavier elements.

29
Q

How is a white dwarf formed?

A

The star remains a red giant for about a billion years before throwing if a shell of gas. The rest of the star is pulled together by gravity and collapses to form a white dwarf. No fusion reactions happen here here and it gradually cools over another billion years to being become dwarf.

30
Q

What are red supergiants?

A

Stars that have 4x the mass of our star or more are brighter and hotter. They fuse hydrogen into helium faster to become red super giants.m

31
Q

How does a supernova form?

A

At the end of a red supergiant period the star rapidly collapses and then explodes into a supernova. The outer layers of the red supergiant are cast of and expand outwards.

32
Q

How is a black hole formed?

A

If what is left of the supernova is 4x the mass of our sun then gravity pull the remains together to form a black hole.

33
Q

What happens if the remain of a giant star are not 4x the mass of our sun?

A

They turn into neutron stars. Gravity pulls them together to form a small very dense Neuton star.

34
Q

Can light escape a black hole?

A

No because the gravitational pull of a black hole is so strong.

35
Q

What is the cycle of a normal star?

A 
Nebula
Protostar
Main sequence
Red giant
Shell of gas
White dwarf
36
Q

What is the cycle of a massive star?

A 
Nebula
Protostar
Massive main sequence star
Red super giant
Supernova 
Black hole or neutron star
37
Q

How do we know black holes exist if we can’t see them?

A

We can’t see them directly because light can’t escape form them. However they pull in gases from the space around them and these become very hot as they fall into the black hole. The hot gases emit radiation that we detect.

38
Q

What is the Doppler effect?

A

-

39
Q

Why is the pitch of a sound lower behind a moving object?

A

The sound behind a moving source becomes stretched, making wavelength longer. This in turn lowers the frequency so we hear it as a lower pitch. The opposite happens in front of the sound source.

40
Q

What did the pitch of a sound spend on?

A

The frequency of the sound wave.

41
Q

The Doppler affect can only occur when…

A

The source of the sound is moving relative to the observer. Of you are travelling at the same velocity the sound would not appear to change.

42
Q

What is redshift?

A

Waves emitted by something moving away form an observer have their wavelength increased and frequency decreased compared to eaves from a stationary object.

The red shift is the measure of how far along the spectrum the lines have moved.

43
Q

What does the redshift of objects mean?

A

It means that it is moving away from us. The further the lines are shifted that faster the space object/star/galaxy is moving relative to us.

44
Q

What would appear if the space object/star/galaxy was moving toward us?

A

The wavelength and frequency of light waves becomes shorter so the pattern of lines moves towards the blue end of the spectrum.

45
Q

How can we interpret the universe is expanding through redshift?

A

The further away a galaxy is the greater the redshift and so the faster it is moving away from us we interpret this relationship to mean that the universe is expanding.

46
Q

What does the Big Bang theory state?

A

The who.e I oversee and its matter started out as a tiny point of concentrated energy about 13.5 billion years ago. The universe expanded from this and is still expanding. As the universe expanded gravity caused matter to clump together to form stars.

47
Q

What does the steady star theory state?

A

This theory says that the universe has always existed and is expanding. New matter is continuously created within the universe as it expands.

48
Q

Similarities between Big Bang theory and steady state theory:

A
  • Both state that the universe expanding.

- observations of redshift in the light form other galaxies can be used as support for both theories.

49
Q

Differences between Big Bang theory and steady state theory:

A

CMB radiation provides supporting evidence for Big Bang Theory. Steady state theory cannot explain this.

50
Q

What is CMB radiation?

A

Cosmic microwave background radiation.

Microwave radiation receive form all over the sky. Originated from Big Bang.

51
Q

What is the different between a red giant and a red supergiant?

A

Red giant: a star that has used up all its hydrogen in its core and is now using helium as a fuel. Bigger than a normal star.

Red supergiant: a star that has used up all its hydrogen in its core but has a mass much larger that the sun.

52
Q

What is a supernova?

A

An explosion produced when the core of a red supergiant collapses.

Physics (11 decks)

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