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edexcel igcse physics > unit eight: astrophysics > Flashcards

unit eight: astrophysics Flashcards

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1
Q

orbit

A

the gravitationally curved path of an object around a point in space

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2
Q

perihelion

A

the point in orbit closest to the sun

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3
Q

aphelion

A

the point in orbit furthest from the sun

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4
Q

orbital speed =

A

(2 x π x orbital radius) / time period

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5
Q

circumference of a circle

A

2 x π x r

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6
Q

gravitational field strength of earth

A

10 N/kg

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7
Q

gravitational field strength of the moon

A

1.6 N/kg

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8
Q

first stage of a star life cycle

A

stellar nebula

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9
Q

what is the star life cycle for a high mass star

A
  1. high mass star
  2. red supergiant
  3. supernova where matter and energy are…
  4. flung into space
  5. neutron star
  6. black hole
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10
Q

what is the life cycle of a low mass star

A
  1. low mass star
  2. protostar
  3. red giant
  4. white dwarf
  5. black dwarf
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11
Q

how many stars are in the milky way

A

100-400 billion

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12
Q

how wide is the milky way

A

105,700 light years

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13
Q

what is the temperature of the suns core

A

15 million Kelvin/celsius

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14
Q

what is the distance from the sun to earth

A

150 million km

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15
Q

what is the temperature of the suns surface

A

6000 Kelvin

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16
Q

what surface temperature is an O classed star

A

more than 33,000K

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17
Q

what colour is an O classed star

A

blue

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18
Q

what surface temperature is a B classed star

A

33,000 - 10,000K

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19
Q

what colour is a B classed star

A

blue - white

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20
Q

what surface temperature is a A classed star

A

10,000 - 7500K

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21
Q

what colour is a A classed star

A

white

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22
Q

what surface temperature is a F classed star

A

7500-6000K

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23
Q

what colour is a F classed star

A

yellow - white

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24
Q

what surface temperature is a G classed star

A

6000 - 5200K

25
Q

what colour is a G classed star

A

yellow

26
Q

what surface temperature is a K classed star

A

5200 - 3700K

27
Q

what colour is a K classed star

A

orange

28
Q

what surface temperature is a M classed star

A

3700 - 2000K

29
Q

what colour is a M classed star

A

red

30
Q

what is the variable displayed on the vertical axis of the Hertzsprung-Russell Diagram

A

absolute magnitude (m)

31
Q

what are the three main sections of a Hertzsprung Russell Diagram

A

supergiants, main sequence and white dwarfs

32
Q

how are planets and moons visible

A

they reflect light from the sun

33
Q

how does the sun release vast amounts of energy

A

it is fuelled by a continuous nuclear reaction

34
Q

what are comets

A

relatively small objects consisting of rock and ice

35
Q

what does gravitational force depend on

A

size of masses involved, and distance between the masses.

36
Q

if size of mass increases, then the force of gravity

A

increases

37
Q

if the distance between masses increases, then the force of gravity

A

decreases

38
Q

what is apparent brightness/apparent magnitude

A

a measure of how bright the star appears from the Earth

39
Q

what does the apparent brightness depend on

A

what the star is made from and the kinds of nuclear reactions taking place, and the distance the star is from Earth

40
Q

what is the absolute brightness/absolute magnitude

A

a measure of how bright the star would appear if they were all placed the same distance (10 parsecs) from the Earth

41
Q

what is the luminosity

A

a measure of the amount of light energy emitted from the stars surface every second

42
Q

how do nuclear fusions begin in stars

A

hydrogen nuclei join to make larger nuclei and huge amounts of energy are released as heat and light

43
Q

when is a star stable

A

when the high temperatures and pressures generated to try and push the star apart generate an outward force in the star, but it is balanced with gravity providing an inward force that tries to push the particles together

44
Q

how does a star become a red giant

A

as the hydrogen runs out, frequency of collisions decreases and the rate of hydrogen fusion decreases. the gravitational forces are now dominant and begin to compress the star and temperatures reach the point where fusion reactions can occur between helium nuclei.

45
Q

how does a star become a white dwarf

A

the helium runs out, but further fusion reactions take place to produce larger nuclei. the gravitational forces cause the star to collapse inwards, increasing its core temperature even more

46
Q

when does a star become a neutron star (life cycle)

A

if the remaining core after the supernova is less than 3 times the mass of the sun

47
Q

when does a star become a black hole

A

if the remaining core after the supernova is more than 3 times the mass of the sun.

48
Q

if a light source is moving, describe the movement of the light waves

A

the wavefronts will no longer be equally spaced, and the ones ahead of the light source will be compressed and have a shorter wavelength, meaning they will have a higher frequency and be blue. ones behind the light source will be stretched out, have a longer wave length and be red.

49
Q

how fast does electromagnetic radiation travel?

A

300 million m/s

50
Q

light from galaxies moving towards us leads to a

A

blueshift

51
Q

light from galaxies moving away from us leads to a

A

redshift

52
Q

what do you need to know to measure how fast the galaxies go

A

how large the redshift or blueshift is

53
Q

if we see a redshift, that means the universe is expanding, meaning

A

at some point in the past all the matter in the universe was condensed in a single point which it expanded from

54
Q

what is cosmic microwave background radiation

A

during the big bang a lot of high energy cosmic rays would have been produced. as the universe has expanded the space the waves have travelled through has also expanded. this has increased their wavelength and have gradually moved through the EM spectrum to become microwaves. they can be detected from all directions supporting the idea that all matter and energy originated at one point

55
Q

how long ago was the big bang

A

13.7 billion years ago

56
Q

change of wavelength / wavelength =

A

velocity of galaxy / speed of light

57
Q

what is the symbol for wavelength

A

λ

58
Q

how would you calculate change of wavelength

A

final wavelength - inital wavelength

59
Q

what is the speed of light

A

3 x 10 to the power of 8

edexcel igcse physics (13 decks)

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