Astrophysics - GCSE Flashcards

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1
Q

what is our solar system part of?

A

It is part of a huge galaxy

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2
Q

how many galaxies are there?

A

billions upon billions

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3
Q

what is the universe a large collection of?

A

billions of galaxies

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4
Q

what is the definition of a galaxy?

A

a large collections of stars

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5
Q

what galaxy are we part of?

A

the milky way galaxy

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6
Q

what is the distance between the neighbouring stars (stars close to one another) in the galaxy?

A

it is millions of times greater than the distance between planets in our solar system

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7
Q

what is the name of the force that keeps the stars together in a galaxy?

A

gravity

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8
Q

what is the movement that galaxies do?

A

they rotate

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9
Q

how apart are galaxies from each other?

A

millions of times further apart than the stars within a galaxy

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10
Q

how is the space inside the universe?

A

it is mostly empty and really, really, really big

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11
Q

how many stars does our solar system contain? and what is its name

A

one, and it is called the sun

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12
Q

how many planets does the solar system contain and what are they?

A

it contains 8:

  • mercury
  • venus
  • earth
  • mars
  • jupiter
  • saturn
  • uranus
  • neptune
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13
Q

how would you describe our solar system?

A

stuff that orbits around the sun

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14
Q

what are the things you can find inside our solar system?

hint: there are 6 things

A
  • planets
  • dwarf planets
  • moons
  • artificial satellites
  • asteroids
  • comets
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15
Q

what are planets?

A

they are large objects that orbit a star

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16
Q

what are dwarf planets?

A

they are planet-like objects that aren’t big enough to be planets

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17
Q

give an example of a dwarf planet?

lembra de JESSIE

A

pluto

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18
Q

what are moons?

A

they are what orbit planets with almost circular orbits. They are a type of natural satellite

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19
Q

what are artificial satellites?

A

what usually orbit the earth in fairly circular orbits and are man made

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20
Q

what are asteroids? and where are they usually found

A
  • lumps of rock and metal that orbit the sun

- usually found in the asteroid belt

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21
Q

what are comets? how are their orbit? and where do they travel?

A
  • lumps of ice and dust that orbit the sun
  • their orbits are usually highly elliptical (a very stretched out circle)
  • some travel from near the sun to the outskirts of our solar system
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22
Q

how is the structure of the solar system determined?

A

it is determined by orbits

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23
Q

what is the definition of orbits?

A

paths that objects take as they move around each other in space

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24
Q

what does gravity provide?

A

it provides the force that creates orbits

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25
Q

how do planets move around the sun?

A

it almost circular orbits

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26
Q

what is happening when an object is travelling in a circle?

hint: 3 points to be made

A
  • it is constantly changing directions
  • it is constantly accelerating
  • the is always a force acting on it
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27
Q

what is the name of a force that acts when an object is travelling in a circle? and how is it acting?

A

it is called centripetal force and it acts toward the centre of the circle

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28
Q

what is instantaneous velocity?

A

the thing which is at a right angle to the acceleration

29
Q

what keeps the object travelling in a circle?

A

the instantaneous velocity

30
Q

what is the force that makes all planets and comets stay in their orbit?

A

the gravitational force (gravity) of the sun

31
Q

what does the force due to gravity depend on?

A

it depends on mass and distance

32
Q

what is the definition of weight?

A

the force on an object due to gravity

33
Q

the variation of weight of any object depends on what?

A

it depends on the strength (g) of the gravitational field that is in it

34
Q

what does the gravitational field strength depend on (vary with)?
(hint: there are 2 points to be made)

A
  • it depends on the mass of the body creating the field (the larger the mass of the body the stronger its gravitational field)
  • it varies with distance (the closer you get to a planet the stronger the gravitational force is)
35
Q

give an example of gravitational field strength depending on mass

A

the earth is more massive than the moon, so an object would weight more on earth than it would on the moon.

36
Q

if the force is stronger, what else is needed to increases so that it can be balanced?

A

the instantaneous velocity

37
Q

the closer you get to a star or planet what will you need to do to remain in the orbit?

A

you will need to move faster

38
Q

if the speed of an object in a stable orbit changes, what else will need to change?

A

the size (radius) of its orbit

39
Q

how will faster moving objects move in a stable orbit?

A

it will move with a smaller radius than slower moving ones

40
Q

what does having different planets orbiting the sun at different speed means?

A

it means that the distance between planets vary over time

41
Q

what is the orbit of moons and planets usually like?

A

it usually is slightly elliptical

42
Q

what does the word elliptical mean?

A

elongated

43
Q

how do comets orbit the sun?

A

their orbit is very elliptical and orbits with the sun at one focus

44
Q

what has a longer orbital period than the earth?

A

comets

45
Q

why do comets have a longer orbital period than the earth?

A

they have a longer orbital period because they travel from the outer edges of our solar system, meaning it is more far from the sun then earth is

46
Q

what happens to a comet when it is near the sun?

A

it travels much faster when it is near the sun

47
Q

why do comets travel faster when it is nearer the sun?

A

it travels faster because the increased pull of gravity makes it speed up the closer it gets to the sun

48
Q

how long is some artificial earth satellites orbital period.

A

one day = 24 hours

49
Q

what are earth satellites called?

A

geostationary satellites

50
Q

why are geostationary satellites useful?

A

it is useful in communication because they are always over the same part of the planet

51
Q

how do you calculate speed?

A

speed = distance / time

52
Q

how do you calculate the distance of a circular orbit?

distance travelled is the circumference of the orbit

A

distance = 2 x Pi x radius of orbit

53
Q

how do you calculate the orbital speed?

A

orbital speed = 2 x Pi x orbital radius / time period

54
Q

how do you calculate radius?

A

it is always half the length of the diameter. This means that if the diameter is 4 you need to divide 4/2 which gives you 2

55
Q

what do stars go through during their life?

A

they go through some dramatic transformations

56
Q

what is the first step of a star transformation?

A

1) stars initially form from a cloud of dust and gas called NEBULA

57
Q

what is the second step of a star transformation?

A

2) forces of gravity pulls the dust and gas together to for a PROTOSTAR. Temperature rises as star gets denser and more particles collide with each other. A star is born (not the movie hehehe)

58
Q

what is the third step of a star transformation?

A

3) star enters a looong stable period. The energy produced by nuclear fusion tries to expand the star, it balances the force of gravity pulling everything inwards. This stable period the star is called MAIN SEQUENCE STAR and it typically lasts several billion years. The larger the mass of the star, the shorter it’s time on the main sequence.

59
Q

what is the fourth step of a star transformation?

A

4) The star is compressed until it is dense and hot enough that the energy (and pressure) created makes the outer layers of the star expand. The star becomes RED GIANT (if it is a small star) or a RED SUPERGIANT (if it is a larger star) It becomes red because the surface cools

60
Q

what is the fifth step of a star transformation?

A

5) RED GIANT then becomes unstable and ejects its outer layer of dust and gas. This leaves behind a hot, dense solid core - a WHITE DWARF

61
Q

what is the sixth step of a star transformation?

A

6) RED SUPERGIANT starts to glow brightly again as they undergo more fusion to make heavier elements . They expand and contract several times, as the balance the shifts between gravity and thermal expansion. Eventually they explode in a SUPERNOVA

62
Q

what is the seventh step of a star transformation?

A

7) 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 massive enough, it will collapse and become a BLACK HOLE

63
Q

what is a black hole?

A

a super dense region of space that not even light can escape from

64
Q

what is the simple (non-boring) description of a star’s life cycle?

A

nebula -> protostar -> main sequence-> red giant -> white dwarf
or
nebula -> protostar -> main sequence-> red supergiant -> supernova -> neutron star
or
nebula -> protostar -> main sequence-> red supergiant -> supernova -> black hole

65
Q

what is a way to classify stars?

A

by their colours

66
Q

what does the colour of a star depend on?

A

on the visible light it emits

67
Q

how much light each star emits depends on what?

A

on the star’s surface temperature

68
Q

what are the colours used to classify stars?

hint: there are 5 colours

A
  • blue
  • white
  • yellow
  • orange
  • red
69
Q

what is the list of hottest to coolest stars?

A

1) blue
2) white
3) yellow
4) orange
5) red