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Physics > Topic 7-Astronomy > Flashcards

Topic 7-Astronomy Flashcards

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1
Q

What does the solar system look like?

A
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2
Q

What is the sun?

A

A star.

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3
Q

How many main planets are there?

A

8.

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4
Q

What is one of the dwarf planets?

A

Pluto.

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5
Q

What else does the solar system contain apart from planets?

A

Moons, asteroids and comets.

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6
Q

What are moons?

A

Natural satellites that orbit planets.

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7
Q

What is the solar system a tiny part of?

A

The milky way.

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8
Q

What is a galaxy?

A

A massive group of stars.

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9
Q

How many stars does the milky way contain?

A

Hundreds of billions of stars.

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10
Q

How many galaxies are there?

A

Hundreds of billions.

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11
Q

What do stars form from?

A

Clouds of dust and gas.

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12
Q

What is a cloud of dust and gas?

A

A nebula.

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13
Q

What is the main gas in a nebula?

A

Hydrogen.

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14
Q

What is the first stage of stars forming?

A

Gravity causes the cloud of dust and gas to collapse. As the dust particles move faster, the temperature rises to millions of degrees Celsius.

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15
Q

What is the collapsing cloud of hot gas and dust called?

A

A protostar.

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16
Q

What is the second stage of a star forming?

A

If the temperature of the protostar gets high enough then hydrogen nuclei join together to form hellium. This is nuclear fusion. At this point a star has been formed.

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17
Q

What happens after the star has been formed?

A

Nuclear fusion is now releasing a huge amount of energy.

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18
Q

What are the two opposing forces acting within a star?

A

Gravity acts inwards and can make the star collapse. The energy from nuclear fusion acts outwards and makes the star expand. When the forces are balanced the star is in equilibrium.

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19
Q

What is a satellite?

A

Something with a smaller mass orbiting something with a larger mass in space.

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20
Q

What causes satellites to orbit?

A

Centripetal force caused by gravity.

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21
Q

Are planets satellites?

A

Yes to the sun.

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22
Q

What are artificial satellites?

A

Ones we have put into orbit our self.

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23
Q

What is a low polar orbit?

A

Vertical orbiting round the poles of the earth (artificial).

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24
Q

What is a geostationary orbit?

A

When the satellite orbits around the equator. Orbits once per day.

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25
Q

Would a closer or farther away orbit have more force?

A

The closer orbit would have more force and therefore would travel quicker.

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26
Q

What is the movement of satellites like?

A

Accelerating in a circle despite being at a constant speed.

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27
Q

Where is the resultant force acting?

A

Towards the centre of the circle.

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28
Q

What causes an orbit?

A

Object falling to earth and same velocity as earth is falling away from it.

29
Q

What do main-sequence stars do?

A

They fuse hydrogen to make helium but this releases a huge amount of energy.

30
Q

How long can stars stay in the main sequence phase for?

A

A very long time.

31
Q

What does the phase after main-sequence depend on?

A

The size of the star.

32
Q

What happens to stars that are about the same size as out sun?

A

The hydrogen begins to run out so the outwards force is less than the inwards force 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 then expands to form a red giant. At some point the red giant stops fusing helium and shrinks to form a white dwarf. Because the white dwarf is no longer carrying out fusion it gradually cools down. Eventually it stops releasing any energy and forms a black dwarf. Universe is not old enough to have seen any of these.

33
Q

What happens to stars much bigger than the sun?

A

Once these stars run out of hydrogen, they leave the main sequence stage and expand into red super giants. Helium nuclei now fuse together to produce heavier elements. The red super giant stops carrying out nuclear fusion and explodes which is called a supernova. The temperature of a supernova is high enough to produce elements heavier than iron. When the supernova explodes the elements are distributed throughout the universe. After the supernova the remains of the star can form one of two objects. The first is a neutron star and consists of neutrons densely packed together. The second is a black hole, black holes have such a large gravity than even light cannot escape.

34
Q

What can nuclear fusion not do?

A

Make any element heavier than iron.

35
Q

What causes the high temperature in protostars?

A

Friction between particles.

36
Q

What is around a white dwarf?

A

A planetary nebula.

37
Q

What happened in the 1900s?

A

Astronomers were looking at the light emitted from different galaxies and they detected the the light from very distant galaxies has an increased wavelength compared to light from closer galaxies.

38
Q

What are the dark lines in the spectrum for?

A

Certain elements in the Sun absorb light of specific wavelengths so those wavelengths apear as dark lines.

39
Q

What happens to the black lines when looking at light from a distant galaxy when compared to the sun?

A

The lines will shift slightly towards the red end of the spectrum.

40
Q

What does the red shift tell us?

A

That the galaxies are moving away from each other. Because the galaxies are moving away the light waves are stretched so the wavelength increases. Further away galaxies are moving away faster and have a bigger red shift.

41
Q

What is the evidence that the universe is expanding?

A

The fact that distant galaxies are moving faster than nearby galaxies.

42
Q

What do scientists believe the universe began from?

A

A very small region that was very hot and dense. This expanded and is called the big bag theory.

43
Q

What did astronomers notice in 1988?

A

They believed that gravity caused expansion of universe to slow down but observations of supernovae show that the rate of expansion is actually increasing. Dark matter/ dark energy that we cannot detect explains why the expansion in increasing.

44
Q

What would you see if an object was coming towards us?

A

A blue shift.

45
Q

What did we originally think the solar system was like?

A

Ptolemy put forward the Geocentric model in which the sun and all planets orbit the earth. This was due to observations using naked eye.

46
Q

What happened once telescopes were invented?

A

They found the geocentric model was false.

47
Q

What did Copernicus put forward?

A

The heliocentric model in which the sun was at the centre of our solar system.

48
Q

What did the invention of telescopes in the late 16th century lead to?

A

Galilei discovered four of Jupiter’s moons by plotting their movements.

49
Q

Where are most asteroids found?

A

In-between the orbits of Mars and Jupiter.

50
Q

What does our current model of the solar system look like?

A

8 planets, 5 dwarf planets, that all move in elliptical orbits around the sun.

51
Q

What does the GFS on the surface of a body depend on?

A

The mass of the body and the distance from its centre to its surface. Bigger mass and smaller radius.

52
Q

What are artificial satellites used for?

A

Communications and to observe the earth and space. TV transmissions.

53
Q

What is a comet?

A

A ball of dirty ice.

54
Q

How do comets orbit?

A

Highly elliptical around the sun with the tail facing away from the sun as the warmth causes the tail.

55
Q

Where do comets spend most of their time?

A

Outside the solar system.

56
Q

What are highly elliptical orbits used for?

A

Used for communication for parts of the Earth near the poles.

57
Q

What are polar orbits like?

A

Satellites will eventually pass over all parts of the earth.

58
Q

What are circular gestational orbits used for?

A

They remain over one point of the Earth and are used for broadcasting. They move at 3070 m/s.

59
Q

What are low Earth satellites used for?

A

They need the least fuel and are used for launching satellites. These satellites in low Earth orbit move at 7500m/s.

60
Q

What happens if satellites in low Earth orbit slow down?

A

They need the most speed to orbit so they will fall towards Earth and gain speed as it falls until it is moving fast enough to stay in a new lower orbit until it encounters the top of the atmosphere where it will slow it down and cause it to fall to earth.

61
Q

How old is the universe according to the big bang theory?

A

13.5 billion years old.

62
Q

What is the steady state theory?

A

Suggested later than the big bang theory (1920s) in 1948 and says that the universe has always existed and is expanding and that new matter is continuously being created within the universe as it expands.

63
Q

What is cosmic background radiation?

A

The big bang theory says that huge amounts of radiation was released at the beginning of the universe and because the universe is expanding, the wavelength of this radiation has increased and so now it is only detectable as microwave radiation. This was discovered in 1964 when 2 astronomers were building a radio telescope.

64
Q

What does CMB show support for?

A

The big bang theory as the steady state theory cannot explain the CMB radiation.

65
Q

Explain radio telescopes.

A

Very expensive but they are versatile as they are not weather or light dependent.

66
Q

Explain optical telescopes.

A

Cheaper gut limited to nighttime use and require a clear sky.

67
Q

Explain telescopes outside the earths atmosphere.

A

Hard to repair but are clearer as the atmosphere absorbs a lot of radiation and has light pollution.

68
Q

What are larger planets like?

A

More gaseous and have stomper gravitational field so attract debris to form a ring.

69
Q

Are comets just ice and why do they form a tail?

A

Rock too and it’s because they melt.

Physics (9 decks)

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