P6 - space phy Flashcards
how does the days work
-sun goes from east to west because of the earth’s rotation on its own axis
what controls the tides
moon
why can you see the moon at night
-it reflects the sun’s light
time taken for the moon to completely orbit around the earth
27.5 days/ 1 month
moon phases
-the moon’s orbit relative to the earths change, results in varying sunlight on different parts of the moon
-its a natural satellite of earth
time taken for the earth to completely orbit around the sun
365 days
seasons
-caused by the earth’s axis being tilted so different hemispheres receive varying amounts of sunlight = diff seasons
eg. summer & winter/ spring & autumn
-countries near the equator don’t have seasons as they receive direct sunlight all year
-the further the country from the equator, the more noticeable the season changes
order of the 8 planets from the Sun
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-Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune
-rocky planets - Mercury, Venus, Earth, Mars
-gas giants - Jupiter, Saturn, Uranus, Neptune
-Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto have moons
-there’s an asteroid belt btw Mars & Jupiter
what orbits the Sun
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-dwarf planets - Pluto, Eris
-moons that orbit planets
-asteroids & meteoroids
-comets
what hold the celestial objects that the orbit the sun
-the sun’s gravitational pull
-greater the distance, the weaker the gravitational pull, slower orbital speed
-planets size affects the gravitational pull
heaviest object in the solar system
sun
what are moons
natural satellites that orbit planets
what are asteroids & meteoroids
lumps of rock
what are comets
-at their farthest distance form the Sun, they’re made of frozen gas, rocks & dust
-as they move to the sun, they warm up & release a trail of gas & dust behind them
-orbits the sun in irregular paths
origins of the solar system
from a nebula, a large rotating cloud of gas & dust
accretion disk
flat rotating disk made by the spinning motion of the nebula
formation of planets
-planets were formed from the leftover material from the nebula that wasn’t drawn into the sun’s gravitational pull
-through accretion, smaller particles (gas & dust) were pulled tgt by gravity to form larger rocks = Rocky planets
-the heat of the sun pushed the lighter materials away from it to form Gas Giants
speed of light
3 x 10^8 meters per second
elliptical
the shape of the the orbits around the sun
eccentricity
how much the orbit path deviates from a perfect circle
why are orbits elliptical
-at the start, the object travels past the sun due to its own momentum from the big bang
-When it gets close to the sun, the sun’s gravity pulls it
-the object speeds up & its kinetic energy carries it to its furthest point of the orbit
-the object then slows down & is pulled back to the sun again
formula for orbital speed
2πr
——— = orbital speed (meter per second)
t
-orbital speed - speed of a planet in an orbit around the sun
-r - orbital radius - average distance from the planet to the sun
-t - orbital period - time taken for 1 complete orbit
define star
-ball of hot gas & plasma that is powered by nuclear fusion in its core
-usually has hydrogen & helium
define nuclear fusion
process of merging small nuclei into larger -nuclei to release energy
-needs high temp & pressure to start
define neubla
-region of space containing gas (mostly hydrogen) & dust
-interstellar hydrogen clouds
define protostar
dense hot ball or gas formed by a collapsed nebula
define main sequence of stars
stable period of a star when it fuses hydrogen in its core
why do stars look like they’re twinkling
their light passes through the moving air in the earth’s atmosphere
milky way galaxy
-collections of many stars, dust & gas that are held together by gravitational forces
-rotates around its center, 240 millions years for 1 turn
-all the stars inside it move at a constant motion
-diameter is 100 000 light years
difference btw galaxy & universe
-galaxy - collections of stars, dust & gas that are held together by gravitational forces
-universe - collection of galaxies
Big bang theory
-the Universe expanded from a single point of high density and temperature
-Universe is still expanding
-Universe is approximately 13.8 billion years old
what is the closest star to earth
Sun
stars
-nuclear fusion releases lots of energy & heats up the star
-very hot so they emit electromagnetic radiation, including visible light
-approximately spherical shaped
-size of star depends on the amount of material absorbed from the original nebula
-star’s life cycle depends on its size
-move at a constant motion
betelgeyse
-bigger than the sun
-star in the constellation of Orion
-cooler star than sun = reddish colour
Procion B
-smaller than the sun
-star in the constellation of Canis Minor
-hotter than the sun = white colour
why does the sun and other stars look different
-sun if the closest star to earth so it is seen as a bright sphere. Other stars are very far away so they look like faint points of light
note: nebula from a supernova may form new stars with orbiting planets
define planetary nebula
glowing shell of ionizing gas
life cycle of a star about the size of the sun
-interstellar hydrogen clouds
-protostar
-main sequence
-red giant; hydrogen in its core is exhausted, fusion slows down, core contracts under gravity, outer layers expand & cool
-planetary nebula - red giant ejects it out layers
-white dwarf
-black dwarf; after white dwarf cools & fades
life cycle of a star bigger than the size of the sun
-interstellar hydrogen clouds
-protostar
-main sequence
-red supergiant; fusion continues & forms heavy elements
-supernova; fusion stops, core collapses due to gravity, outer layer explodes & releases lots of E
-neutron star; object with mostly neutrons
OR
-black hole; strong gravity that its pulls light
define supernova
explosion of a star
will the sun become a black hole
no, it’s too small
dust
-fine particles of material that was formed in older stars
-these stars have exploded & scattered the dust in the Milky way
life cycle of stars
-nebula collapses
-protostar
-star
start of a protostar
-formed in a nebula
-nebula collapses when disturbed by stars or objects that pass by
-nebula collapses due to the gravitational forces between gas & dust particles that pulls them closer; as they get closer, they start to accelerate towards each other; nebula become dense
-gravitational forces compress the nebula into a sphere that is denser than the original nebula = protostar
-individual particles move very quickly = temp of the ball of gas is high
-some material from the nebula forms a disk that rotating around the protostar. The material may form planets
protostar
-pressure & temp at core is higher than that on the surface
-gravitational forces pull the material inwards
-pressure from the hot core pulls the material outwards
-They balance & create a stable star
-if protostar continues to absorb material, its size, gravitational force, pressure & temp increases
protostar to star
-pressure in a protostar is eventually high enough for nuclear fusion reactions
-nuclear fusion releases lots of gamma radiation in its core which heats all material absorbed by the star. The heat increases the rate of reactions
-it is now hot enough to emit radiation (infrared, visible light, UV) of its surface
eg. fusion of 2 hydrogen nuclei = helium
-it starts the main sequence of its life
main sequence of stars
-during this period, the star is fairly stable in its size & temp while fusion hydrogen in its core
-smaller the star, slower it uses up its hydrogen fuel & spend more time in the main sequence
similarities btw protostar & star
-both are rotating balls of hot gas
-both pressure & temp increase towards the center
differences btw protostar & star
-star has nuclear fusion, protostar doesn’t
be careful of units
rearrange order of cards
