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gcse science > Science - Physics - Space Physics - P8 > Flashcards

Science - Physics - Space Physics - P8 Flashcards

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1
Q

what’s a nebula ?

A

a cloud of dust and gas that stars initially form

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2
Q

what does gravity turn a nebula into ?

A

protostar

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3
Q

what is a protostar ?

A

a cloud of dust and gas which clumps together due to gravity

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4
Q

what does the gravitational attraction do to the protostar ?

A

causes its density to increase so the particles within the protostar increases and particles within the protostar collides more frequently, causing the temperature to rise

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5
Q

what happens when the temperature in the protostar gets too high ?

A

hydrogen nuclei undergos nuclear fusion to form helium nuclei which gives out lots of energy and keeps the core of the star hot

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6
Q

how is a star born ?

A

-hydrogen nuclei undergos nuclear fusion when temperature rises too much to form helium nuclei
-this gives out massive amounts of energy which keeps the core of the star hot
- star is born

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7
Q

how are planets made ?

A

smaller masses of gas and dust around the star may be pulled together to make planets which orbit the star

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8
Q

what happens after a star has been formed ?

A

it enters a long, stable period

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9
Q

how is a star stable once it has been formed ?

A
  • energy released by the nuclear fusion provides an outward pressure that tries to expand the star which balances the force of gravity pulling everything inwards
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10
Q

what is another word for a star being stable ?

A

a star being in equilibrium

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11
Q

what is a main sequence star ?

A

the star when it is in a stable period

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12
Q

how long does a main sequence star roughly last for ?

A

7 billion years

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13
Q

give an example of a main sequence star ?

A

sun

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14
Q

what happens at the end of a main sequence stars life ?

A
  • hydrogen runs out
  • fusion of helium occurs and the star is no longer a main sequence star
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15
Q

what do stars produce ?

A

all naturally occurring elements in the universe

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16
Q

how do stars about the size of the sun die ?

A
  • small star about the size of the sun expands into a red giant when it starts to run out of oxygen
  • it then becomes unstable and ejects its outer layer of dust and gas as a planetary nebula
  • this leaves behind a hot, dense, solid core - a white dwarf
  • as a white dwarf cools down it emits less energy
  • when it no longer emits a significant amount it becomes a black dwarf
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17
Q

what is a red giant ?

A

what the star expands into when it runs out of hydrogen

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18
Q

why is a red giant red ?

A

because the surface of the star cools

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19
Q

what is a white dwarf ?

A

a hot dense solid core which is left behind from a planetary nebula

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20
Q

what is a planetary nebula ?

A

formed when a red giant becomes unstable and ejects a layer of dust and gas

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21
Q

what is a black dwarf ?

A

formed when a white dwarf cools down - something which eventually disappears in sight

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22
Q

what happens when stars much larger than the sun die ?

A
  • expands into red super giants when they start to run out of hydrogen
  • they expand and contract multiple times forming elements less heavy than iron
  • when red super giants runs out of elements to use they become unstable
  • they explode into a supernova forming elements heavier than iron, ejecting them into the universe forming planets and stars
  • the exploding supernova throws the outer layers of dust and gas into space leaving a very dense core called a neutron star
  • if the star is big enough it becomes a black hole instead
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23
Q

what are red super giants ?

A

formed from stars larger than the sun, they expand and contract multiple times when stars start to run out of oxygen, forming elements as heavy as iron in nuclear reactions

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24
Q

how is a supernova formed ?

A

when red super giants run out of elements to fuse and become unstable and explode into a supernova

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25
Q

what do supernovas do ?

A

form elements heavier than iron and ejects them into the universe to form new planets and stars, throwing outer layers of dust and gas into space

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26
Q

how are neutron stars formed ?

A

when supernovas throw out lots of layers of dust and gas into space, they leave behind a neutron star with a dense core

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27
Q

what is a black hole ?

A

a dense point in space so not even light can escape from it

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28
Q

how is a black hole formed ?

A

when a neutron star is big enough it becomes a black hole

29
Q

what star does the solar system contain ?

A

the sun

30
Q

what is the solar system made up of other than the sun ?

A

it is made up of everything that orbits the sun

31
Q

what is an orbit ?

A

the path on which one object moves around another

32
Q

what is the sun orbitted by ?

A
  • planets
  • dwarf planets
  • satellites
33
Q

what is a planet ?

A

large objects which orbit a star

34
Q

how many planets orbit the sun ?

A

8

35
Q

what makes something a planet ?

A
  • they have to be large enough to have gravity strong enough to have pulled in any nearby objects apart from their natural satellites
36
Q

what is a dwarf planet ?

A

planet-like objects which orbit stars but are too small

37
Q

give an example of a dwarf planet ?

A

pluto

38
Q

what is a satellite ?

A

objects that orbit a second more massive object

39
Q

what are the 2 types of satellite ?

A
  • natural satellites
  • artificial satellites
40
Q

what is a natural satellite example ?

A

the moon

41
Q

what is an artificial satellite ?

A

satellites humans have built

42
Q

what is galaxy is our solar system a part of ?

A

milky way

43
Q

what is a galaxy ?

A

a massive collection of billions of stars that are all held together by gravity

44
Q

what keeps an object within its object ?

A

gravity

45
Q

what does it mean if an object is moving in a circle ?

A

it is constantly changing direction which means it is constantly accerlerating

46
Q

what needs to happen for an object to accelerate ?

A

there must be a force acting on it

47
Q

for circular motion what direction is the force at ?

A

towards the centre of the circle

48
Q

what is the force acting towards the centre of the circle in objects in our solar system ?

A

gravitational force - between a planet and the sun

49
Q

what is an orbit a balance between ?

A

the force providing the acceleration and the forward motion of the object

50
Q

what keeps an object travelling in a circle when it is orbiting ?

A

instantaneous velocity

51
Q

what is instantaneous velocity ?

A

velocity which is at right angles to the acceleration and force of gravity

52
Q

what does the size of orbit depend on ?

A

an objects speed

53
Q

the closer you get to a star or planet, what happens to the gravitational force ?

A

it gets stronger

54
Q

the stronger the gravitational force, what does the object need to travel in to stay in orbit ?

A

the faster the object needs to travel

55
Q

for an object in a stable orbit if the speed of the object changes, what happens ?

A

the size (radius) of it orbit must also change

56
Q

if the object moves faster, what happens to the size of its object ?

A

it is smaller

57
Q

what is red shift ?

A

the shift in observed wavelength of light from a source moving away from a stationary observer. The wavelength is shifted towards the red end of the electromagnetic spectrum

58
Q

when does red shift occur ?

A

when the source of light is moving away from the observer - the light wave is ‘stretching out’ as the source moves away

59
Q

as the light from most distant galaxies has been red shifted, what does this suggest about the galaxies ?

A

they are moving away from us

60
Q

what do measurements of the red shift indicates ?

A

most distant galaxies are moving away from us very quickly

61
Q

which kind of galaxy has a greater red shift ?

A

distant galaxies

62
Q

what does distant galaxies red shifting further away from us than closer ones suggest about us ?

A

galaxies are moving away from each other = the universe is expanding

63
Q

what is the big bang theory ?

A
  • initially all matter in the universe was occupied in a very small space - this tiny space was very dense and very hot
  • then it exploded and space started expanding - the expansion is still going on
64
Q

what is the big bang theory supported by ?

A

red-shift measurements so is the generally accepted theory

65
Q

how do scientists come up with theories like the big bang ?

A

observations

66
Q

what happens when scientists find new evidence which isn’t explained by their current theory ?

A

they have to make a new theory or change a current one to explain what they have observed

67
Q

give an example of an unexplained observations that scientists have found about space ?

A
  • galaxies are moving away from us faster and faster
  • scientists think the universe is mostly made up of dark matter and energy, and are seen as the reasons for the accelerated expansion of the universe - but no one knows what they are
68
Q

what is dark matter ?

A

the name given to a known substance which holds galaxies together but does not emit any electromagnetic radiation

gcse science (27 decks)

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