P8.3 Flashcards
spec approved
what is the doppler effect?
physical phenomena by which there is a change in the observed frequency/wavelength of a wave (due to relative motion between observer and source
what is red shift?
and what does it imply
the shift in wavelength of the lights from distant stars/galaxies to longer wavelengths
- implies stars moving away from us
what is blue shift?
and what does it imply
the shift in wavelength of the lights from distant stars/galaxies to shorter wavelengths
- implies stars moving towards us
how is red shift linked to the big-bang model?
- light from distant galaxies is red shifted
so galaxies are moving away from us - and so if all galaxies are moving away from each other, at one point all matter must have existed at a single point in space
how does the distance of a galaxy (away from earth) affect the red-shift?
further away = greater red-shift
means it is moving away faster
what is a spectrum?
the range of frequencies/colours observed when light from a source is dispersed into separate wavelengths
how do we know if light is red shifted?
the black lines (which correspond to specific wavelengths of light absorbed by certain atoms in the star)
- have been shifted towards longer wavelengths
what is the second piece of evidence for the big bang theory?
cosmic background radiation
CMBR
what is strange about cosmic background radiation?
it fills the universe almost uniformly
describe how CMBR gives evidence for the big bang theory
- at beginning of universe, all energy manifested as short gamma rays
- universe expanded = radiation stretched out to longer wavelengths
- ie. microwave radiation
- suggests all started off at single point (as evenly fill the universe)
what is the steady state theory?
idea that all of the universe appeared at the same time
do scientists think that the galaxies themselves are moving?
no, but the space between them is somehow expanding
how was CMBR discovered?
in 1960, two scientists placed sensors.
detected microwave radiation coming from all directions
how was our sun formed?
dust and gas drawn together by gravity
what allows fusion reactions to occur in stars?
- gravitational attraction between dust particles draws them closer
- so temp + pressure increases
- so particles can fuse together
how does an equilibrium form within a star?
energy released during fusion balances the gravitational collapse due to gravity
what are the 8 planets of the solar system (and order)
- give mnemonic to remember it
my very easy method just speeds up naming (planets)
```
mercury
venus
earth
mars
jupiter
saturn
uranus
neptune
pluto
~~~
what 5 things make up the solar system, and describe briefly what they are
sun
star at the centre of the solar system
planets
spherical bodies that orbit the sun
moons
spherical bodies that orbit planets
minor planets
small spherical objects that orbit the sun
comets
dust/ice that orbit the sun with long (elliptical) orbits
what are the inner planets?
mercury, venus, earth, mars
what are the outer planets?
jupiter, saturn, uranus, neptune
major difference between inner and outer planets?
inner = rocky, have an atmosphere
outer = gas giants (rings and lots of moons)
What is the asteroid belt?
and where is it
pieces of rock left over from the formation of the solar system (between jupiter and mars)
how does a protostar become a main sequence star?
- particles pulled together by gravitational force
- becomes denser and hotter
- particles speed up
- particles collide more energetically
- nuclear fusion begins
describe the life cycle of a star
- dust + gas gather under gravity = protostar
- once protostar = hot + dense enough, nuclear fusion begins = main sequence star
- star is stable in main sequence EQUILIBRIUM
ie. radiation pressure outwards (fusion) = gravitational attraction inwards - radiation pressure drops (no more hydrogen nuclei to fuse)
- gravitational force collapses star
- fusion of heavier elements begin
- star expands (either red giant, or red super giant)
TERRIBLE DESCRIPTION LOOK AT SME
why do stars expand when the fusion of heavier elements begin?
- energy of fusion increases
- radiation pressure increases
(greater than gravitational attraction)
what is the last stage of the life cycle of a small star?
- fusion slows down
- radiation pressure decreases
- gravitational force collapses star
- heats up = white dwarf
- eventually cools = black dwarf
what is the last stage of the life cycle of a large Star?
- lots of heavier nuclei fuse to release LOTS of energy
- large increase in radiation pressure outwards
- larger than gravitational pull inwards
- star explodes to supernova
- dense neutron star forms
(if very dense = black hole)
simple description of life cycle of low mass star?
protostar
↓
main sequence star
↓
red giant
↓
white dwarf (+ planetary nebula)
↓
black dwarfsimple description of life cycle of high mass star?
protostar
↓
main sequence star
↓
red super-giant
↓
supernova
↓
neutron star
↓
(if high mass)
black holecompare inner and outer planets
inner - mostly rocky
outer - mostly gas
inner - small mass, small gravitational fields, few moons
outer - large mass, large gravitational fields, many moons
why is the sun not expanding?
balance between force of gravity inwards and radiation pressure from nuclear fusion outwards
why do larger planets tend to have rings and more moons
- larger mass = larger gravitational pull
attracts debris/plents
what does the intensity and the wavelength of emitted radiation depend on?
temperature of the body
