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uoft year 1 semester 1 > AST201 midterm > Flashcards

AST201 midterm Flashcards

1
Q

who was Fritz Zwicky?

A

a swiss astronomer that discovered ‘missing mass’ in galaxy clusters during the 1930’s.

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2
Q

who was vera rubin?

A

an astronomer that observed how stars in the outer reaches of the galaxy moved. she realized that stellar orbital speed increased with distance from center of the galaxy

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3
Q

what was rubin’s original hypothesis, and what was it based on?

A

according to Newton’s law of gravity, stars should orbit faster closer to the center of the galaxy and slower away. this turned out to be false.

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4
Q

newton’s first law of motion:

A

objects in motion remain in motion unless acted upon by an external force.

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5
Q

newton’s second law of motion:

A

the change in speed is equal to the applied force divided by the mass of the object. a=f/m

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6
Q

newton’s third law of motion:

A

for every applied force, there is an equal and opposite reaction. the ball pushes on you as hard as you push on it.

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7
Q

who is charles bolton?

A

he studied blue giant star cygnus in 1971, determining it was in a binary orbit with an unseen object of about 155 solar masses. cygnus x-1 was the first widely accepted stellar mass black hole.

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8
Q

the supermassive black hole at the middle of the milky way is

A

Sagittarius A

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9
Q

what did cecelia payne do?

A

she used spectrography to find out the composition of the sun

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10
Q

what did edward pickering do?

A

he created the harvard astronomical computers.

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11
Q

who was williamina fleming?

A

she was a harvard astronomical computer and created the henry draper catalogue.

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12
Q

who was henrietta swan?

A

she was a harvard astronomical computer and discovered the cepheid variable star period-luminosity relationship.

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13
Q

who was annie jump cannon?

A

a harvard astronomical computer that formed the OBAFGKM sequence by analyzing stellar spectra with her own eyes.

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14
Q

what is the OBADGM system called?

A

morgan keenan system

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15
Q

percentages of the universe:

A

ordinary matter: 4.9%
dark matter: 26.8%
dark energy: 68.3%

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16
Q

define ‘invariance of light’

A

the concept that all light rays travel at the same speed, regardless of outside factors, independent of frame of reference.

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17
Q

why is einstein’s theory of special relativity special?

A

because it only deals with cases where the reference frames move at constant speeds

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18
Q

what is einsteins theory of special relativity?

A

that all laws of physics are the same in all reference frames that move at constant speeds

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19
Q

if two clocks are synced and one stays on earth and the other is put on an airplane, which will have passed through less time?

A

the one on the airplane

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20
Q

moving clocks…

A

run slow

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21
Q

what is relativistic speed?

A

the speed at which the effects of special relativity can be felt

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22
Q

how many forces?

A

four

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23
Q

what are the four forces?

A

electromagnetism, gravity, weak nuclear force, strong nuclear force

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24
Q

electromagnetism:

A

carrier particle: photon. range: infinite.

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25
Q

strong nuclear force:

A

carrier particle: gluon

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26
Q

weak nuclear force:

A

carrier particle: w and z bosons

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27
Q

gravity:

A

range: infinite. carrier particle: ‘graviton’ ?

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28
Q

what is the acceleration of gravity on earth

A

9.8m/s

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29
Q

what is einstein’s equivalence principle?

A

the idea that the laws of physics will work the same in an accelerating frame of reference and in a gravitational field

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30
Q

how did einstein’s theory of general relativity come to be?

A

he generalized his theory of special relativity to account for accelerating frames of references.

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31
Q

how and what did general relativity replace?

A

general relativity replaced newton’s concept of gravity with the idea of gravity as a consequence of spacetime curvature instead of a force

32
Q

define gravitational lensing

A

where massive objects bend the space around them, forcing light to follow its curved contours

33
Q

if spacetime is curved by mass, objects…

A

must follow curved trajectories

34
Q

how many lines of evidence for the existence of black holes?

A

five

35
Q

name all the lines of evidence for the existence of black holes

A
  • xray binary systems
  • direct imaging via the event horizon telescope
  • gravitational wave measurements of black hole mergers (gravitational wave detectors)
  • motion of stars around sag a
  • tidal disruption events
36
Q

define escape speed

A

the speed required to break free of an objects gravity

37
Q

define black hole

A

a region of space where matter is compressed so densely that the escape speed exceeds the speed of light

38
Q

define event horizon

A

the outer boundary of a black hole where the escape speed is the speed of light

39
Q

define singularity

A

the center point of a black hole, where the density goes into infinity

40
Q

define Schwarzschild radius

A

the distance between the singularity and the event horizon

41
Q

what are the four size ranges of black holes

A

microscopic, stellar mass, intermediate, supermassive

42
Q

what is the sun made of

A

mostly hydrogen, a bit of helium

43
Q

define spaghettification

A

the vertical stretching and horizontal compression of objects into long, thin shapes, caused by extreme tidal forces

44
Q

gravitational time dilation means that

A

a clock would appear to stop at the event horizon of a black hole

45
Q

red wavelengths are short or long

A

long

46
Q

blue wavelengths are hot or cool

A

hot

47
Q

define blackbody

A

an idealized object that absorbs all wavelengths of light

48
Q

define spectrograph

A

something that breaks light from a single material into its component colours

49
Q

define spectral lines

A

weaker or stronger regions in an otherwise uniform and continuous spectrum

50
Q

as the temperature of a blackbody decreases, its wavelength…

A

increases

51
Q

the conversion rate of mass to energy is

A

the speed of light squared (meaning that a small amount of mass produces a huge amount of energy)

52
Q

define binding energy:

A

the force that holds things (like nuclei) together

53
Q

the isolated proton has a mass of

A

1.00728 AMU

54
Q

the mass of four combined protons is:

A

4.00260 AMU

55
Q

theoretically what should the mass of four protons be? what is the discrepancy?

A

it should be 4.02912 AMU. there is a 0.7% discrepancy.

56
Q

protons cannot be bound with the x force and must use the y force

A

cannot be found with electromagnetism and must be bound by the strong nuclear force

57
Q

are neutrons bigger or smaller than protons

A

bigger

58
Q

neutrinos only interact with which forces

A

weak nuclear force and gravity, making them ‘ghostly’

59
Q

define luminosity:

A

how intrinsically bright something is

60
Q

define apparent brightness:

A

how bright something appears to be

61
Q

apparent vs absolute magnitude

A

apparent measures apparent brightness, absolute measures luminosity

62
Q

what is the square inverse law of light

A

the apparent brightness is simply the luminosity of the star divided by the surface area of the sphere into which it emits light

63
Q

what does a hertzspring russell diagram measure

A

surface temperature vs luminosity

64
Q

the stefan boltzman equation tells us

A

the relationship between luminosity, temperature, and radius

65
Q

main sequence stars are called

A

dwarf stars

66
Q

what type of star is most numerous in the universe

A

m class stars, red dwarfs

67
Q

the masses of stars increase while lifetime…

A

decreases

68
Q

stars not on the main sequence no longer…

A

fuse hydrogen in their cores

69
Q

the stars above n below the main sequence

A

above: dying
below: dead

70
Q

ratio of main sequence stars

A

one o/b star to every 200 k/m star

71
Q

how many luminosity classes

A

5

72
Q

what are the five luminosity classes in order

A

supergiants, bright giants, giants, subgiants, main sequence stars

73
Q

which of the stars in the luminosity classes are alive

A

only type five

74
Q

two types of star clusters

A

open and globular

75
Q
A

uoft year 1 semester 1 (3 decks)

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