Astrophysics Flashcards
pneumonic for the planets
My Very Educated Mother Just Served Us Noodles
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
why are objects in orbit kept in motion
Objects in orbit are kept in motion due to the pulling force exerted by gravity
The bigger the mass of an object, the stronger its gravity
what is gravitational force
Gravitational force = attraction between objects with masses
what does gravitational force depend on
Gravitational force depends on:
masses of both objects
distance between the two objects
Increasing mass increases the gravitational force, but increasing distance decreases the gravitational force
what is a satellite
A satellite = an object that orbits a planet
There are natural and aritifical (manmade) satellites
Natural satellite = the moon
Most planets have moon (some have multiple moons)
what type of orbits do moons have
Moons have circular orbits with their planets
what are artificial satellites used for (2)
Artificial satellites are used for communication over large distances (as this is over large distances, this needs to be higher in orbit) ⟶ international phone calls/video links, internet
Some satellites put into lower orbits are used for monitoring ⟶ temperature of the world’s oceans, forest fires, and other details about the Earth’s surface
what are comets
Comets = large rock-like pieces of ice that orbit the Sun
what type of orbits do comets ave
Comets have elliptical orbits (oval) ⟶ this means that at one point it will be orbiting very close to the Sun, but at others it will be closer to the edge of our solar system
what is gravitational field strength
Gravitational field strength = how strong gravity is ⟶ the symbol for this g
what affects Gravitational Field Strength
For planets, their mass and radius affects the size of their gravitational field strength
Larger mass means larger g
Larger radius means there will be lower g at the surface
what is the equation for weight
weight=mass x gfs
what affects the orbital speed ofa satellite
Orbital speed of satellites depends on the tasks they are performing
describe the flowchart of life for main sequence starts (5)
Life Cycle of a Star:
Gravitational forces pull particles together (this includes dust and gas particles)
Once a cloud of these particles forms, nuclear reactions begin ⟶ they release lots of energy, creating very high temperatures
These high temperatures cause the particles to expand, which is an outward force pushing the particles apart
The star enters its main stable period when the inward gravitational forces and the outward forces from the expansion of the particles become balanced
This is a main sequence star (our Sun right now is at this stage)
describe th flowchart for the life cycle of a star similar to our sun (9) after main sequence
FOR STARS SIMILAR SIZE TO OUR SUN:
The nuclear reactions eventually come to a stop near the end of this stable period ⟶ because eventually the hydrogen nuclei become less and less
When this happens, the gravitational forces become bigger than the outward forces pushing the particles apart
This surge in gravitational forces compresses the star
As the star shrinks, there is a large increase in temperature ⟶ the star becomes hot enough that nuclear fusion cant start between helium nuclei (all the hydrogen has fused to now form helium)
The energy released from these nuclear fusion reactions causes the particles to expand, and makes the star many times bigger than it previously was
As the star expands, and cools a little bit, its light energy is emitted in red part of the spectrum ⟶ it becomes a red giant
Once the helium nuclei have fused, new nuclear reactions begin however the compressive forces are larger so the star begins to contract
As the star compresses, the temperature increases, which causes the colour to change to blue and white light ⟶ white dwarf star
As the white dwarf star cools it becomes a cold black dwarf star.
describe the flowchart of the life cycle of a star much larger than our sun (6) after main sequence
FOR STARS MUCH LARGER THAN OUR SUN:
From the main sequence star, it becomes a red supergiant
At the end of this red supergiant period, it contracts, and it becomes unstable
It explodes and throws dust and gas into space to form a new stellar nebula
This exploding star = the supernova
After the explosion, the remaining matter forms a very dense neutron star
If the neutron star has a mass about 5x bigger than star, it will collapse and become a black hole
what is the HR diagram used for
The Hertzsprung-Russell diagram is used to show the relationship between the brightness, temperature and classification of a star
This diagram is used for us to find a star’s position in it and know its internal structure and the stage the star is in, in its life cycle
Make a flashcard saying to draw out the HR diagram (Hertzsprung-Russell Diagram) - the shape and position of the different stages of stars
see whatsapp
give an example of the doppler effect
As a race car gets closer, its pitch sounds higher (its frequency increases) and as it moves away its frequency appears to decrease - this apparent change of frequency to your relative position is the Doppler effect
describe the dopper effect red shift diagram
The Doppler effect is a property with all waves - including sound and light
When astronomers, look at light emitted by stars in space, they can see the Doppler effect
In flashcards put to refer to the diagram on whatsapp
The black lines are absorption lines ⟶ these are where certain frequencies of light have been absorbed by hydrogen
As you go from the Sun to each galaxy further and further away, the lines are all shifting towards the red end of the spectrum ⟶ this movement/displacement is red shift
what is red/blue shift
Red-shift shows that light waves emitted from the star/source are moving away from the observer
Blue-shift indicates that the source of light is moving towards the observer
why does red shift happen
Light emitted from a star moving away from us needs to travel a longer distance than when it was first emitted, so the wavelength stretches and becomes longer ⟶ we see red shift
why does blue shift happen
Light from a star moving towards us becomes compressed and has a shorter-wavelength so we see blue shift
what is a common fact about the universes size
As the universe is expanding, all the galaxies within it are getting further apart
