Space Physics Flashcards
(28 cards)
Nebula
a cloud of dust and gas
Protostar
the force of gravity pulls the dust + gas together (causes the Nebula to collapse)
formation of a Main sequence star
protostar 🡢 main sequence star
Temperature rises, more particles collide.
When the temperature is high enough nuclear fusion occurs:
Hydrogen nuclei 🡢 helium nuclei
a huge amount of energy is released which keeps the star hot
Nuclear fusion
the process by which two light atomic nuclei combine to form a single heavier one while releasing massive amounts of energy
Main sequence star
Typically last several billion years
-long stable period
-the outward pressure caused by nuclear fusion which tries to expand the star is balanced by the force of gravity pulling everything inwards
Red giant/red supergiant
The hydrogen begins to run out and the star swells. It becomes red because the surface cools.
The fusion of helium (+other elements) occurs. Heavier elements (up to iron) are created in the core of the star.
White dwarf
The star becomes unstable and ejects its outer layer of dust + gas. It leaves behind a hot, dense solid core - a white dwarf.
Black dwarf
As a white dwarf cools, it emits less energy. When it no longer emits a significant amount, it is called a black dwarf.
Supernova
Big stars (red supergiants) start glowing brightly again + undergo more fusion (expand + contract several times), forming elements as heavy as iron in nuclear reactions.
Eventually they explode in a supernova, forming elements heavier than iron + ejecting them across the universe to form new planets and stars.
Neutron star
Exploding supernova throws the outer layers of dust + gas into space, leaving a very dense core called a neutron star.
Black hole
If the star is big enough, it will become a black hole - a super dense point in space that not even light can escape from.
Life cycle of a small to medium sized star (Sun)
nebula
protostar
main sequence star
red giant
white dwarf
black dwarf
Life cycle of a big star
nebula
protostar
main sequence star
red supergiant
supernova
neutron star/black hole
Planets
Large objects that orbit a star
-have to be large enough to have ‘cleared their neighbourhoods’ (their gravity has to be strong enough to have pulled in any nearby objects) - apart from their natural satellites
Planets in our solar system
Mercury My
Venus Very
Earth Easy
Mars Method
Jupiter Just
Saturn Speeds
Uranus Up
Neptune Nothing/Naming
Dwarf planets
e.g. Pluto
Planet-like objects that orbit stars, but don’t meet all of the requirements to be a planet
Moons
Type of natural satellite that orbit planets
Artificial satellite
Satellites that humans have built
Generally orbit the Earth
Orbits
Planets move around the sun in circular orbits. Moons move around planets in circular orbits.
Gravity provides the force that creates orbits
Orbit - an object travelling in a circle - constantly changing direction, therefore constantly accelerating. Therefore constantly changing velocity NOT speed.
To accelerate, a force (gravitational energy) must be acting on an object. This is directed towards the centre of the circle. The object is already moving 🡢 causes the object to change its direction. (the object is moving so it doesn’t go straight to the centre of the circle). Object keeps accelerating toward what it’s orbiting but the instantaneous velocity (which is at a right angle to the acceleration) keeps it travelling in a circle.
The force that makes this happen is provided by the gravitational force (gravity) between the planet and the Sun (or satellites).
Size of orbit
Depends on objects speed
-closer to a planet, stronger gravity 🡢 stronger force, the faster the object needs to travel to remain in orbit.
Faster will have a stable orbit with a smaller radius than slower moving ones.
Red-shift
Wavelengths of light from distant galaxies have increased in distance - longer. They’ve shifted towards the red end of the spectrum. Wave frequency has decreased. Wavelength has increased.
Red-shift provides evidence for the Big Bang
Suggests the source of light is moving away from us
Measurements of red-shift show that more distant galaxies have greater red-shifts than nearer ones. 🡢 this means they’re moving away faster than nearer ones.
🡢Conclusion: the universe is expanding - the Big Bang was once condensed and has since moved outwards.
Big Bang
All matter in the universe occupied a very small space
-it was very dense and very hot
-it ‘exploded’ and space started expanding - space is still expanding
Dark matter
Name given to an unknown substance which holds galaxies together, but does not emit any electromagnetic radiation.
