igcse physics astrophysics Flashcards
the sun
-a huge glowing ball of gas (a star)
-extremely hot, 6000°C on surface and 15,000,000°C in its center
-energy is released by nuclear reactions in its core
-most of its energy is radiated as infrared, visible and UV rays
the earth
-turns slowly on its axis once a day
-half of the earth is in sunlight and half in shadow
-as it moved from light to shadow, it passes from day into night
-only planet that supports life
temperatures of regions of the earth
area A and B can receive the same amounts of energy but on different surface areas.
the more spread out the energy, the less thermal energy there is as it is less concentrated.
earth’s movement
-it moves around the sun in circular paths (orbits) which take 365 days
-earths axis is tilted by 23.5°
-which causes regions on earth to get varying hours of daylight/ varying climate condition and seasons throughout the year
two reasons for the higher temperature in summer
- because of the tilt, the surface may be more concentrated in energy
-more hours of sunlight
season
- December: winter in north, summer in south
- March: equal hours of day and night
- June: summer in north, winter in south
- September: equal hours of day and night
the moon
-smaller than earth
-moves around earth in a near-circular orbit
-each orbit takes 27.3 days to turn once on its axis (so moon keeps the same face towards us)
-surface of the moon reflects sunlight, allowing us to see it, the rest of the surface is in shawdows
orbital speed
distance= 2πr
speed= d/T
r=3.84x10^5
T=27.3 days/ 655.2 hours
s= 3.68x10^3
the solar system
-planets are not hot enough to give off their own light, so they’re only seen when it is reflecting sunlight
-planets are kept in orbit by the gravitational pull
-planets travel around the sun in the same direction and almost same plane
-the further a planet is from the sun, the slower it travels and more time it takes to complete an orbit, and the lower its average surface temperature
the inner planets
Mercury
Venus
Earth
Mars
the outer planets
Jupiter
Saturn
Uranus
Neptune
Pluto
Mercury
-closest to the sun
-crated surface
-no atmosphere
Venus
-brightest object in the night sky
-almost same size as earth
-covered by thick clouds of sulfuric acid
-its atmosphere causes a greenhouse effect (97% CO2)
Mars
-called red planet bcs of its surface color
-has an atmosphere, dusty surface, and polar caps
-water may once have flowed there
-has no active volcanoes
Jupiter
-more massive than all other planets put tgthr
-mainly gas, its atmosphere has 90% hydrogen and has no solid surface
-one of its moons have active volcanoes
Saturn
-mainly gas
-surrounded by very thin rings (millions of pieces of ice ranging in size which orbit around it)
Uranus
-gas giant
-has rings that are much fainter than Saturn’s
-its axis rotation is tilted at more than 90°
Neptune
-outermost of the gas giants
-has faint ring system
Pluto
-small in size
-most astronomers don’t consider it a main planet
Comets
-highly elliptical orbits, in some cases can take them beyond Pluto and then close into the sun
- there is icy lumps (several of kms long) in the heads of the comments
-has a tail (millions of kms) from sun heat, dust and gas, which is visible bcs of sunlight reflection
meteor
earth runs into tiny grains of material which hit the atmosphere so fast that they burn up, which causes a streak of light
meteorite
a large chunk of material reaches the ground without completely burring up
objects in the orbit
- each mass can attract other mass by gravitational force, so any object will go in a circular track in the orbit
gravitational force depends on..
mass (directly)
distance squared (inversly)
satellite
-orbits around more massive objects
-in a low orbit, it needs higher speed and vice versa
-a satellite in a geostationary orbit will always seem like its in the same position from the ground, bcs its period of orbit matches with the earths rotation, the distance is 35900 km so it will need a speed of 11100km/h
light years equation
distance travelled by light in one year
d= speed (3x10^8) x time(365x24x60x60)
d= 9.5 x 10^10 km
-means that a start will take this many years to reach us
galaxy
-galaxy contains a large number of stars including the sun
-between stars there is a thing spread gas and dust called interstellar matter
-over galaxy is called milky way
-a billions of galaxies = universe
big bang theory evidence
galaxies appear to moving parts, they may once have been tgthr in the same space
the big bang theory
- it was not an explosion into existing space, space itself started to expand
-galaxies separating bcs the space between them is increasing
the universe as balloon
as balloons inflates, all the parts inside appear to move away from each other. the more the distant, the faster they recede
-no single galaxy is at the center of expansion
age of the universe
1/ Ho
Ho= 2.3x10ˉ¹⁸
so = 4.3 x10¹⁷ seconds
red shift
-objects move away from the earth at high speed, light waves become stretched out, so the wavelengths shift toward the red
blue shift
-objects move toward the earth at high speed, light waves become, so wavelength is shifted towards the blue
expanding universe
light from distant galaxies is red shifted, so they are moving away from us, so we are living in an expanding universe
doppler effect theory
-the universe and time began many billions of years ago from a single hot superatom erupted in a burst of energy called the big bang
this is where all the matter in the universe came from
birth of a star
1.starts life as a cloud of dust and gas called nebula, then its collapsed by gravity
2.protostar: more temp, so faster movement of particles
3.nucleur fusion: hydrogen nuclei join tgthr to form helium nuclei
4.main sequence star stage
death of stars (same size of the sun)
- hydrogen starts to runs out
2.outward force due to fusion is less than inward force of gravity
3.star collapses inward, temp increases
4.helium nuclei fuse tgthr, star expands forming a red giant
5.helium nuclei stops to fuse forming a white dwarf
6.cools down bcs no energy forming a black dwarf
death of star larger than the sun
1.hydrogen nuclei runs out
2.helium nuclei fuse tgthr forming a red super giant
3.red super giant expands and explodes called a supernova, this makes elements heavier than iron
4.either becomes black mole or neutron star
