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physics > Astronomy - topic 6 > Flashcards

Astronomy - topic 6 Flashcards

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1
Q

what are planets

A

large objects which orbit a star

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2
Q

what are dwarf planets

A

similar to planets but too small

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3
Q

what are satellites

A

objects that orbit a second more massive object

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4
Q

what are asteroids

A

lumps of rock and metal that orbit the sun

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5
Q

what are comets

A

lumps of ice and dust that orbit the sun

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6
Q

why do objects travelling in a circle not have constant velocity

A

velocity is speed with direction, and direction is always changing when moving in a circle and so velocity can’t stay the same

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7
Q

planets closest to the sun

A

mercury
venus
earth
mars
jupiter
saturn
uranus
neptune

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8
Q

what is the orbit of a comet

A

elliptical

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9
Q

what is the orbit of planets and satellites

A

almost circular

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10
Q

what are optical telescopes used for

A

detecting other parts of the EM spectrum

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11
Q

what are telescoped used for

A

to see distant objects clearly and to observe the universe

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12
Q

what does a larger aperture mean

A

better image quality

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13
Q

why are telescopes better on mountains

A

less light and air pollution

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14
Q

geocentric model

A

earth is at the centre of solar system and everything orbits the Earth in perfect circles

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15
Q

why was the geocentric model at the time was accepted

A

people didn’t have telescopes so they had to use the naked eye and they saw the sun and moon travelling across the sky in the same direction

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16
Q

what was the heliocentric model

A

the idea that the sun is at the centre of the universe and everything orbits the sun in perfect circles

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17
Q

what was the evidence disproving the geocentric model

A

Galileo, while looking at Jupiter saw stars near the planets, and the stars never moved away but along with the planet. This shows not everything moved around the Earth

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18
Q

why are bigger telescoped better

A

better resolution and they can gather more light so we can see things we previously couldnt and better magnification

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19
Q

what is the doppler effect

A

change in frequency and wavelength. This happens because the waves bunch together in front of the source and stretch out behind it

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20
Q

what is red shift

A

when we look at light from many distant galaxies we find that its wavelength is longer than it should be and the light we detect is shifted towards the red end of the visible spectrum

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21
Q

what does red shift show us

A

the galaxy the light came from is moving away from Earth and that the universe is expanding

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22
Q

the faster the galaxy moves away from us …….

A

the larger the red shift

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23
Q

how can you measure the red shift

A

looking at absorption spectra

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24
Q

what is CMBR

A

radiation left over from an initial explosion that has cooled over time

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25
Q

what are the 2 theories of the origin of the universe

A

steady state theory and big bang theory

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26
Q

what doe steady state theory say

A

universe has no beginning and it has always existed as it is now and the universe is expanding

27
Q

what does big bang theory say

A

all galaxies are moving away from each other and universe was created from a small point with all the matter in the universe exploding and then expanding

28
Q

evidence for big bang theory

A

CMBR and red shift

29
Q

evidence for steady state theory

A

red shift

30
Q

what is a nebula

A

a cloud of dust and gas

31
Q

life cycle of an average star

A

nebula
protostar
average star
red giant
planetary nebula
white dwarf

32
Q

life cycle of a massive star

A

nebula
protostar
massive star
red supergiant
supernova
neutron star or black hole

33
Q

what does the solar system consist of

A

the Sun, eight planets and their natural satellites, dwarf planets, asteroids and comets

34
Q

what is the orbit of planets like

A

almost circular orbits

35
Q

what is the orbit of moons like

A

circular orbits

36
Q

what is the orbit of artificial satellites

A

almost circular orbits

37
Q

what is the orbit of comets like

A

highly elliptical

38
Q

why does the radius of the orbit of an object in a stable orbit changes size if the speed of the object changes

A

if the object moves faster, the radius of its orbit must be smaller

39
Q

what is a nebula

A

a cloud of dust and gas

40
Q

how is a protostar formed

A

the attractive force of gravity pulls dust and gas together to form a protostar

41
Q

how is a star(main sequence) formed

A

A nebula is a cloud of dust and gas

gravitational attraction causes the density of the protostar to increase as particles within the protostar to collide with each other more frequently so the temperature increases

When the temperature gets hot enough, nuclear fusion occurs, forming a hydrogen nuclei in the core of the star.

lots of energy is given out, which keeps the core of the star hot.

A star is made

42
Q

how is a red giant formed

A

eventually, the hydrogen in the core begins to run out and the force due to gravity is larger than the pressure of thermal expansion.

The star is compressed, until it is dense and hot enough that the energy created makes the outer layers expand.

The star becomes a red when the surface cools

43
Q

what two forces are balanced in the main sequence stage of a stars life

A

gravity and thermal pressure. Gravity is pushing inwards and thermal pressure is pushing outwards

44
Q

what happens to a star if the gravity acting on it is larger than thermal pressure

A

it will turn into a black hole

45
Q

how are white dwarfs formed

A

When a red dwarf becomes unstable and ejects its outer layer of dust and gas as a planetary nebula and this leaves behind a hot, dense solid core - a white dwarf

46
Q

what is the evolution of stars with a mass larger than the sun

A

stars will expand into red super giants when they start to run out of hydrogen

eventually, they become unstable as they run out of elements to fuse and they explode into a supernova, forming elements heavier than iron and eject them into the universe

the exploding supernova throws the outer layer of dust and gas into space, leaving a neutron star

If the star is big enough, it will become a black hole instead

47
Q

how have methods of observing the universe changed over time

A

the earliest telescope was the optical telescope, then telescopes were developed to detect other parts of the EM spectrum so we can learn and see more about the universe

48
Q

how have telescopes improved

A

They are bigger, so they have a better resolution and can gather more light and there is improved magnification

49
Q

why do modern telescoped work alongside computers

A

computers help create clearer and sharper images and make it easy to capture these pictures so they can be analysed later

50
Q

how does lens affect image quality

A

using a larger aperture or higher quality lens will improve the image quality

51
Q

why are some telescopes placed outside the Earth’s atmosphere

A

to observe the frequencies absorbed as the Earth’s atmosphere absorbs a lot of the EM radiation coming from space before it can reach the telescopes on earth

AND

on earth there is light and air pollution

52
Q

what is the doppler effect

A

as a police car moves towards you its siren sounds higher pitched than it would if it were stationary. As it moves away from you its pitch is lower. This change in frequency and wavelength is the doppler effect

53
Q

what is red shift

A

when we look at light from many distant galaxies we find its wavelength is longer than it should be. The light we detect is shifted towards the red end of the visible spectrum, it is redder than the actual light emitted by the galaxy

54
Q

why does red shift of galaxies provide evidence for the universe expanding

A

it shows us that the galaxy that the light came from is moving away from the earth.

55
Q

what is CMBR

A

cosmic microwave background radiation is radiation that comes from all parts of the universe

56
Q

what is steady state theory

A

it says the universe has no beginning and no end, it has always existed as it is now, and it always will and as the universe expands, new matter is constantly created

57
Q

what is the big bang theory

A

the theory says that initially all matter in the universe was occupied in a very dense and hot small space and it exploded. Then, space started expanding and is still expanding

58
Q

how old does the big bang theory day the universe is

A

around 13.8 billion years

59
Q

what is the evidence supporting the steady state theory

A

red shift

60
Q

what is the evidence supporting the big bang theory

A

CMBR and red shift

61
Q

how is red shift used as evidence for both theories

A

both theories state the universe is constantly expanding

62
Q

how is CMBR used as evidence for the big bang theory

A

CMBR is left over energy from an initial energy from an initial explosion that has cooled over time which suggest the universe has a beginning

63
Q

why is the big bang theory the currently accepted model of how the universe began

A

there is more evidence supporting the Big Bang theory than the steady state theory

physics (14 decks)

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