space Flashcards
Explain what happens during the protostar phase:
- a galaxy consists of gas and dust (a nebula)
- between the nebula’s particles is gravitational attraction, which pulls them together.
- as they accumulate, their gravitational potential energy is converted into thermal energy, raising the temperature of the nebula.
- the nebula condenses into a dense core, where the temperature causes particles to have lots of kinetic energy, increasing the thermal energy and pressure as they collide.
- eventually the temperature and pressure is great enough to enable the nuclear fusion of hydrogen into helium.
- the period between the accumulation of gas and dust and nuclear fusion is the protostar phase.
Describe the main sequence:
the main sequence is a star’s longest life phase where it is the most stable. this is because the inward force of gravity and the outwards force of radiational pressure (the force produced by nuclear fusion) are balanced, so the star remains the same shape and size.
Explain what two things can occur after the main sequence (describe what also happens at the end of the main sequence):
if the star is smaller than the sun… when the hydrogen stores get used up in the nuclear fusion of helium, the core collapses further into itself making it denser, under high temperatures and pressures. this allows the nuclear fusion of heavier elements up to carbon and oxygen but isn’t hot or pressured enough for heavier elements this is a red giant. when the hydrogen runs out in the core, due to no more nuclear fusion occurring, the core implodes on itself as the forces of gravity overpower the outward force, when it condenses it increases its temperature and pressure causing it to glow white this is a white dwarf. once the white dwarf cools it becomes a black dwarf.
for stars with a bigger mass than the sun… due to having a greater mass they contain more H so nuclear fusion occurs at faster rates. as the core collapses into itself and becomes denser, the very high temperatures and pressures allow the nuclear fusion of heavier elements up to iron. when the core condenses further, the outer layers experience a weaker force of gravity and start to expand, forming a red supergiant.
what is a supernova?
when the iron core of a red supergiant implodes forming heavier elements than iron and the remnants of the iron core may turn into neutron stars.
formation of black holes:
if the iron core of a red supergiant implodes and creates a remnants greater than 4x the sun’s mass, the neutrons will be so pressured under the gravitational force that it collapses into itself, becoming so dense not even light can escape from it.
why do the cores of stars condense when they run out of hydrogen?
when a star’s core runs out of hydrogen, nuclear fusion cannot occur sustainably so the radiational pressure acting outwards that was originally balancing out the inwards force of gravity weakens, so the inwards force of gravity overrules and causes the core to collapse inwards.
component of our solar system: (8)
sun
planets
moons
gas and dust
asteroids
meteors
dwarf planets
comets
planets in order: (8)
mercury
venus
earth
mars
jupiter
saturn
uranus
neptune
what are asteroids
small irregularly shapes rocks
a region of asteroids is called an asteroid belt
natural satellites
moons (objects that orbits a planet)
what two planets don’t have moons?
mercury and Venus
gas giants
jupiter, saturn, uranus, neptune
thick gaseous and liquid layers around a small core, with rings of ice and rocks.
why isn’t Pluto a planet
too small
too far from the sun
had a different orbiting plane than the rest of the planets
meteors
chunks of rock produces by the collision of asteroids causing them to be launched in other directions, when they enter earths atmosphere, they gain KE and GPE which causes them to burn up making them meteorites.
what is a planet?
a celestial body which orbits around the sun, it has sufficient mass to become relatively spherical in shape and has cleared its neighbourhood.
What is a dwarf planet?
a celestial body that orbits the sun, has sufficient mass to be relatively spherical, has not cleared its neighbourhood and is not a satellite.
Explain how a planet orbits the sun
A planet experiences a force of gravity from the centre of the sun which is an example of centripetal force. the direction of the planet’s orbit acts in right angles to the centripetal force of the sun, therefore its velocity is constantly changing, however, since there are no other opposing forces, the speed stays constant as the resultant force of the planet acts towards the centre.
Why may satellites return back to earth?
because their orbits are in earth’s upper atmosphere, meaning that they experience gravitational drag which slows their speed, therefore the inward force of gravity overpowers the orbit and pulls it to earth’s centre.
for a satellite to remain in orbit, it must be launched at a certain speed and height for it to maintain its circular orbit.
the further it is from the origin of the centripetal force, the less particular speed it travels to remain in orbit as it experiences a weaker force o gravity therefore the longer it takes to do a full obit around
How does the speed of the satellite effect its orbit?
the faster it goes the closer it travels to the centre of gravity, therefore decreases the orbital radius as it needs to experience more gravitational potential energy to remain in orbit.
Explain the red shift theory
the stars and galaxies in space emit light which we can detect those which reach earth. the light can be split by a prism, which we can see some wavelengths have been absorbed by some elements in space such as hydrogen. by comparing these gaps to the gaps found in other light spectrums from other distances we can see whether these distances are moving close or away.
if the gaps in the spectrum are shifting to the red, it means that they are moving away relative to us, the bigger the red shift the faster they are moving away.
Low earth satellite orbits:
- low radius from the earth
- higher speeds to remain in orbit
- orbit the earth every 92 mins
- mapping, and imaging earth
Geostationary orbits
- high orbit
- slower
- orbits every 24 hrs at a fixed spot
- TV communication
the Big Bang theory:
an idea which the universe is expanding constantly, therefore must be expanding from a single point started by a large explosion. this explosion emitted short wavelengths such as gamma radiation, as the universe expanding, the wavelengths stretched to become other parts of the EM spectrum such as radio waves.
scinetists believed that if the universe oginiated from a big bang, high energy radiation must have followed immediately, stretching the wavelengths as it expanded to microwaves.
this theory is supported by our discovery of the cosmic microwaves background radiation (the remnant radiation emitted from the Big Bang), where we saw that microwaves come from everywhere in the universe
the steady state theory:
an idea that the universe is being pushed apart by the formation of space to maintain the universe’s density.
How does dark matter and dark energy explain why the universe is expanding?
dark energy is the energy in space we cannot observe but know is present as the universe is expanding, galaxies require more energy to remain together. dark matter is the matter we theorise to exist as gravity is a consequence of mass, therefore there must be more mass in the universe to keep galaxies together.
