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AQA Higher Physics > 8. Astrophysics > Flashcards

8. Astrophysics Flashcards

1
Q

where are we

A

milky way - 100-400b stars

local group - 150-1000 galaxies

laniakea supercluster - 100,000 galaxies

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2
Q

what is atmospheric composition

A

certain discrete missing frequencies from absorbtion spectra

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3
Q

red shift

A

longer wavelength
moving away

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4
Q

blue shift

A

shorter wavelength
moving towards

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5
Q

magnitude on shift

A

speed

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6
Q

describe the universe

A

homogenous
isotropic

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7
Q

why are we expanidng

A

because 99% of celestial objects are moving away from us

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8
Q

why was the earth at one point dense and hot

A

because expanding = cooling, so we have to have been dense and hot at some point

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9
Q

evidence for the big bang

A

expanding
cmbr
elements

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10
Q

cmbr

A

cosmic microwave background radiation

dense hot point = lots of radiation
universe cools = lower wavelength

homogenous radiation = doppler effect = earth is moving through space

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11
Q

abundance of elements

A

more H and He than other elements

early dense and hot is ideal for H and He to form via fusion

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12
Q

ptolemy’s model

A

earth @ centre

good - correct order
good - moon in right spot
good - circular orbits

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13
Q

galileo galilei

A

ur wrong

  • shadow periodically across jupiter = moons on jupiter
  • mercury sometimes obscured by the sun = wrong order
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14
Q

terrestrial planets

A

rock, metal, minerals

mercury venus earth mars

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15
Q

jovian planets

A

gas giants

jupiter saturn uranus neptune

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16
Q

extra bits beyond neptune

A

oort cloud
kuiper belt

17
Q

planet criteria

A
  1. stable orbit around a star
  2. roughly spherical
  3. clear orbital region
18
Q

asteroid criteria

A
  1. minor planet
  2. terrestrial
19
Q

comet criteria

A
  1. small icy body
  2. eccentric elliptical orbit
20
Q

where do asteroids and comets come from

A

asteroid belts e.g. kuiper, oort

21
Q

satellite criteria

A
  1. orbits a planet
22
Q

centripetal force

A

any force causing an object to follow a circular path

23
Q

what is the centripetal force if the earth is the central body and the moon is the orbiting body

A

weight

24
Q

what are the criteria for centripetal force

A
  1. must be accelerating at a constant speed
    (direction changing, magnitude constant)
  2. no force of weight in the direction of velocity
    (weight and velocity are perpendicular)
  3. no displacement
    (W = Fs = 0)
    (no work done to keep orbit)
25
Q

how to change orbit

A

do work on the orbit
-> changes position within gravitational field of the central body
-> changes the orbital radius

26
Q

what is orbital speed dependent on

A
  1. mass of orbiting body
  2. gfs of central body / centripetal force
  3. orbital radius
27
Q

what is the relationship between orbital speed and orbital radius

A

higher radius = lower gfs = lower weight = lower speed

lower radius = higher gfs = higher weight = higher speed

28
Q

how to measure orbital speed with a little practical

A

measure radius with a ruler and calculate circumference
measure time for multiple rotations with a stopwatch and divide by the amount of rotations for reliability

29
Q

how are stars classified

A

light from stars contains black lines
these lines are frequencies of visible light
these frequencies represent the composition of the atmosphere
this composition has a lot of hydrogen

30
Q

how is the hydrogen actually found

A

energy levels are discrete
excited electrons (when absorbing discrete energy -> certain frequencies -> certain wavelengths)
photons

31
Q

birth of a star

A
  1. stellar nebula
  2. gravitational force pulls in material
  3. more material more grav force

repeat

  1. dense core has high temperature and high pressure
  2. hydrogen overcomes electrostatic repulsion & fuses
  3. protostar
32
Q

how does a protostar go into main sequence

A
  1. the material forms a spherical atmosphere
  2. the core keeps on fusing
33
Q

how does a star stay in main sequence

A

the atmosphere is pulled in by weight
the atmosphere is pushed out by fusion pressure

34
Q

death of a star (hydrogen shell burning)

A
  1. core runs out of H
  2. core contracts
  3. fusion pressure decreases
  4. atmosphere pulled in
  5. fusion pressure increases
  6. fusion pressure > weight
  7. expands and cools
35
Q

death of a red giant

A
  1. red giant keeps expanding
  2. fusion diminishes
  3. heavier elements form (Fe and lower)
  4. fusion pressure decreases
  5. atmosphere collapses and rebounds from core
  6. material thrown out into space (forms a planetary nebula)
  7. core gets left behind and keeps fusing (white giant)
36
Q

death of a big star

A
  1. core runs out of H
  2. fusion pressure decreases
  3. atmosphere collapses
  4. elements heavier than Fe are produced
  5. force of collapse > electron degeneracy pressure
  6. core collapses
  7. outer layers rebound from core @ high velocity
  8. huge shockwave (supernova)
37
Q

> 1.43MSUN

A

neutron star aka pulsar

  • core particles get forced together into densely packed neutrons
  • 20km diameter
  • so dense that the only radiation is from the axis of rotation (radio waves)
38
Q

< 1.43MSUN

A

black hole

  • core continues collapsing into an infinitely dense point (singularity)
  • event horizon around black hole
  • all objects in the EH would need to be > speed of light (300 000 000 m/s) to escape

AQA Higher Physics (4 decks)

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