2 types of orbit
- Geostationary
- Polar
Geostationary orbit + uses?
- 24 hour period
-Orbit earth at the same rate as the earth spins on its axis - Same angular speed as the earth
Uses: communication, satellite TV
Polar orbit + uses?
- 3 hour period
- Orbit the earth quicker and closer than geostationary
- uses: military, google earth, map
What keeps an object in orbit?
-Object moving in a circle is constantly accelerating (changing direction so changing velocity)
-Acceleration requires a force (gravitational force)
-the orbit is the balance between the object’s velocity and the force accelerating in towards the middle of its orbit (gravitational force)
What does the size of the orbit depend on?
- The close the object is to a star/ planet, the stronger the gravitational force
- the stronger the force, the faster the orbiting object needs to travel to remain in orbit
- therefore, for an object in a stable orbit, if the velocity of the object charges, the size of the orbit (radius) must change too
-So faster objects = smaller orbit
Why do astronautS feel weightless?
- There is weight because of mass x gravitational field strength
- but there e is no contact force so they feel weightless
Kepler 3rd law
- for any object in orbit around another object eg the planets orbiting the sun:
Radius of orbit^3 is directly proportional to time period of orbit^2
life cycle of stars if the star is as big as our sun or smaller
- clouds of dust and gas (nebula)
- protostar (nebula)
- main sequence star (yellow dwarf)
- red giant
- planetary nebula
- white dwarf
what happens when a star is clouds of gas and dust? (stage 1 of a star’s life cycle)
- space is clunky and some areas are vacuums whilst some have lots of H2 gas
- gravity pulls dust and gas together
- gravitational energy -> thermal energy
- temperature rises
what happens when a star is a protostar? (stage 2 of a star’s life cycle)
- the temperature continues the rise to 1000 k, so more collisions
- hydrogen undergoes fusion and becomes helium nuclei
- gives out huge amounts of energy which keeps the core of the star hot
- this means a star’s is born
what happens when a star is a main sequence star? (stage 3 of a star’s life cycle)
- stable period of around 10 billion years (where our sun is now) caused by the fusion reactions and gravitation forces being equilibrium
what happens when a star is a red giant/ red super giant ? (stage 4 of a star’s life cycle)
- super giant vs giant depends on size
- red because it is cooling
- eventually hydrogen begins to run out
- fusion of helium and other elements occurs in core of the star hot
what happens when a star that is the same size/ smaller than our sun is a planetary nebula? (stage 5 of a star’s life cycle)
- becomes unstable
- ejects its outer layer of dust and gas
- leaves behind a hot dense core
what happens when a star that is the same size/ smaller than our sun is a white dwarf and black dwarf ? (stage 6 and 7 of a star’s life cycle)
- left with just the core
- as it cools down it emits less and less energy until it becomes a white dwarf
END OF A SMALL TO MEDIUM SIZED STAR’S LIFE CYCLE
life cycle of stars if the star is bigger than our sun
- clouds of dust and gas (nebula)
- protostar (nebula)
- main sequence star (yellow dwarf)
- red super giant or hyper giant
- supernova
6a. neutron star
if the star is big enough
6b. black hole
END OF BIG STAR’S LIFE CYCLE
what happens when a star that is the bigger than our sun is a supernova ? (stage 5 of a star’s life cycle
- start to glow brightly again after being a red super giant/ hyper giant
- undergo more fusion into heavy elements eg iron
- eventually explode into a supernova and the dust, gas and elements heavier than iron are ejected to form new stars and planets
what happens when a star that is bigger than our sun but not the biggest kind is a neutron star ? (stage 6 and 7 of a star’s life cycle
- exploding supernova leaves a very dense core called a neutron star
END OF REALLY BIG STAR’S LIFE CYCLE
what happens when a star that is biggest is a black hole? (stage 6 and 7 of a star’s life cycle
- if it is big enough it will leave a black hole where gravity is so strong not even light can escape
- super dense point in space
- can detect x-ray emitted when gases fall into black holes
END OF BIGGEST STAR’S LIFE CYCLE
What is the Doppler effect?
- As any wave is sent out from a source its motion can make a large difference to the received wave
- if the source is moving away from the receiver, the wave frequency will decrease and wave length increase
- is the source is moving towards the receiver, the frequency will increase as the wavelength decreases
How does the Doppler effect link to red shift?
- The further away a galaxy is, the faster it is moving away so the wave length appears to increase so it ‘shifts’ to the red + infrared end of the visible light spectrum
Significance of red shift
Provides evidence that space itself is expanding →supports big bang theory
What is the big bang theory?
- Theory that suggests that the universe began from a very small region that was extremely hot + dense that exploded and expanded → is still expanding
- since 1998, observation of supernova suggest the distant galaxies are receding ever faster ( expanding at an increasing rate)
Evidence for the big bang
- At the big bang the easy universe was very hot and as it expanded rapidly so it cooled
- the energy in the big bang moved our as it expanded and redshifted as it spread out
-We select this radiation as COSMIC MICROWAVE BACKGROUND RADIATION (red shifted all through em spectrum from gamma to microwave )
What is a satellite? + 2 types
Anything that orbits a planet
1. Natural eg moons
2. Artificial
