space Flashcards
speed of light
3 x 10^8 m/s
what are moons?
natural satellites
when are stars at equilibrim?
when inward force of gravity is equal to the outward force due to pressure
describe the 3 stages of a formation of a star
- starts with a NEBULA- cloud of hydrogen gas and dust
- force of gravity within, pulls particles closer together becomer denser and increasing no. collisions- making star hotter forming PROTOSTAR
- as temperature rises, nuclear fusion of hydrogen nuclei to form helium nuclei occurs in core of the MAIN SEQUENCE STAR
MAIN SEQUENCE STAR is at equilibrium- it is stable
if star formed is smaller than or same size as sun, describe what happens
-
RED GIANT is formed as hydrogen runs out-> fusion dies down -> heats up & the core shrinks due to inward>ouwards | fusion to form heavier elements w helium nuclei in core -> expands again
5.when fusion finishes- star becomes unstable and ejects outer layer of dust and gas known asPLANETARY NEBULA - core collaspse due to force of gravity, cools down, decreasing amouont of energy emitted to form WHITE DWARF
- star cools down until significant energy is lost that is dissapears from sight forming a BLACK DWARF
if star formed is bigger than sun, describe what happens
- RED SUPERGIANT is formed as it runs out of hydrogen -> fusion dies down -> shrinks- inwards> outward | fusion creates heavier elements with helium nuclei -> expands again
- fusion finishes and core collapses causes an explosion of outer remenants to be ejected called a SUPERNOVA where elements heavier iron are produced and distributed across the universe
- inside this SUPERNOVA, a NEUTRON STAR is formed at the centre
- in case of the BIGGESTT stars- the NEUTRON STAR will continue to collaspe under the force of graviy until it forms a BLACK HOLE where it is so dense light cannot escape it
what provides the force that allows satilites and planets to mainatin their circular obits?
and why does it cause constant accerleration
gravity cting towards centre- centripetal force
it causes the orbits to change direction constantly -> velocity is always changing -> its always accerlerating
SPEED REMAINS UNCHANGED
what cause a stable orbit for satlitte
radius indirecty proportional too speed
e.g radius decrease speed increases
if speed and radius increase..
spiral into space because gravitational attraction provides not enough force
planet & moon & comet orbit difference
planet- sligtly elliptical
moon- circular
comet- elliptical
orbital path of comet
closer to sun- looses gpe and gains kinetic- speeding up
causes slighshot efgect, flung into space
moves away- slow down and fall back to sun
define the doppler effect
The change in frequency or wavelength due to the relative motion between source and an observer
wavelengths produced by stationary object vs moving object
stationary- wavelength symmetrical
moving object
- infront of object- the wavelength decreases (freq increases)
- behind object- the wavelength increases (freq decreases)
if an object moves towards an observer…
if an obect moves towards an observer…
wht happens to the wavelength of the light?
- towards observer- wavelength decreases (freq increases)- BLUESHIFT
- away from observer- wavelength increases (freq decreases)- REDSHIFT
motorcycle- away- noise less- freq less
define red-shift
observed increase in the wavelength of light due to source moving away from observer
if red shift is shown in distant galaxies.. what does this tell us?
- universe is expanding- supporting the Big Bang theory
- further away the glaxaxies- the faster its moving away
what is the Big Bang theory?
universe began from a very small region that was extremely hot and dense
there were a series of explosions that caused the universe to expand and is continuing to expand
evidence for big bang theory
- observations in 1998 of the light spectrum from supernovaes suggested distant galaxies are receding ever faster
- light spectrum shows light from distant galacxies are red-shifted- evidence universe expanding
- in an explosion- matter densely packed- explodes and moves all directions- lighter are faster, heavier are slower
- cosmic microwave background radiation- at beginnig- hot & dense- shortwavelngth radiation- now microwaves- showed universe cooled and expanded
what is dark matter
the unseen matter evidenced by rotation and motion of galaxies
what is dark energy
unknown energy that caauses the accerlerated motion of universe and counteraction of gravity
