Space Physics
What's covered
Key facts
Life Cycle of Stars
A star begins to form when gravity pulls together a cloud of dust and gas called a nebula, which contracts into a protostar.
Orbital Motion and Satellites
Satellites in geostationary orbit fly above the equator from west to east, exactly matching Earth's rotation, so they appear to stay over one fixed spot; this suits telecommunication satellites. OCR J249 P8.3e includes geostationary and polar orbits.
Red Shift and the Big Bang
Light from distant galaxies is observed to be shifted towards the red (longer-wavelength) end of the spectrum, an effect called red shift.
The Solar System
Ideas about the Solar System have changed over time: in Ptolemy's model the Earth was at the centre of the Universe (the geocentric model), and Copernicus later switched to a Sun-centred (heliocentric) model. Edexcel 1PH0 7.4P: describe how ideas about the structure of the Solar System have changed over time.
Life Cycle of Stars
A protostar becomes a main sequence star when its core gets hot enough for nuclear fusion of hydrogen into helium to begin.
Orbital Motion and Satellites
Gravity provides the centripetal force that keeps a satellite or planet in a circular orbit, acting towards the centre of the orbit.
Red Shift and the Big Bang
The more distant a galaxy is, the greater its red shift, meaning more distant galaxies are moving away from us faster.
The Solar System
Our Solar System contains one star, the Sun, which has eight planets orbiting it.
Life Cycle of Stars
During the main sequence stage a star is stable because the outward pressure from fusion balances the inward force of gravity.
Orbital Motion and Satellites
An object in a circular orbit moves at a constant speed but its velocity constantly changes because its direction is always changing.
Sample questions
A taste of the 24 questions in this topic, answers marked. Sign up to practise the full set with spaced repetition.
What does a protostar become once nuclear fusion of hydrogen into helium begins?
- •A black hole
- ✓A main sequence star
- •A red giant star
- •A white dwarf star
What provides the centripetal force that keeps a satellite in a circular orbit?
- •Air resistance
- •Magnetic attraction
- ✓The pull of gravity
- •The push of thrust
What does the red shift of light from distant galaxies tell us about the universe?
- •The universe is contracting
- ✓The universe is expanding
- •The universe is rotating
- •The universe is staying the same size
What type of object is the Sun?
- •A comet
- •A moon
- •A planet
- ✓A star
A star about the size of the Sun swells into a red giant. What does it finally become?
- •A black hole
- •A neutron star
- •A supernova
- ✓A white dwarf
For a stable orbit, what happens to the orbital radius if a satellite moves at a higher speed?
- •Its orbital period increases
- ✓Its orbital radius decreases
- •Its orbital radius increases
- •Its orbital radius stays the same
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