Astronomy Flashcards
Does gravity change when you go to other planets and moons
Yes
What is the equation for weight
Weight = mass x gravity
W = mg
What does gravitational force cause these objects to do:
1. Planets in the solar system
2. The moon and artificial satellites
3. Comets in the solar system
- Orbit the sun
- Orbit the earth
- Orbit the sun
What is the equation for orbital speed
Orbital speed = (2 x pi x orbital radius)/time
(2 pi r)/t
How does the orbit of a comet differ from the orbit of a moon or planet
Comets orbit in an elliptical path but moons and planets orbit in a circle
What is a satellite
Something that orbits a larger object in space. Can be natural e.g. moons or man made e.g. telecommunication satellites
What galaxy is the solar system in
The milky way
What is the definition of a galaxy
A large collection of billions of stars
What is the definition of the universe
A large collection of billions of galaxies
What is the definition of the universe
A large collection of billions of galaxies
What is orbital period
The time taken for an object to complete one full orbit
When calculating the orbital radius of the moon, must you include the radius of the earth
Yes - measure from the centre of the earth
What is the time period of the earth orbiting the sun
365.25 days
How long does it take for the earth to rotate on its axis
24 hours
How long does it take for the moon to orbit the sun
One month as an approximation but its actually 27 days
What is the Doppler effect
The apparent change in frequency of a wave due to the relative motion between the source and observer
What is a redshift
The measured wavelength is longer than the emitted wavelength - the object is moving away from the
What is a blueshift
The measured wavelength is shorter than the emitted wavelength - the object is moving towards us
What are the equations for the wavelengths of light and sound (4 parts)
(Observed wavelength - emitted wavelength)/emitted wavelength = change in wavelength/ emitted wavelength = Z (red shift constant) = V/C where c is the speed of light and V is the relative velocity
What is CMB
Cosmic microwave background radiation - after the Big Bang, the radiation emitted cooled as it spread out. A radiotélescope can detect this constant hum of microwaves.
What is the temperature of the universe
2.3K (but it is slowly going down)
What is hubble’s law
The velocity of a galaxy is directly proportional to the distance from earth (straight line graph with gradient of 69.8)
V = H(constant of 69.8)d
How is a red shift shown on a spectra of light
As the lines shift towards the red direction of the spectrum
What is a nebula and what stage is it
First stage - clouds of dust and gas
What does a nebula become and what is it
A protostar - the dust and gas collapse in due to gravity, meaning that the GPE is converted to KE, which increases core temperature. With high enough temperature and pressure, hydrogen fusion occurs, therefore forming a star
What happens after a nebula to an average star
It becomes a main sequence star - like the sun. Hydrogen is fusing to Helium, releasing energy, causing the star to heat up.
What is hydrostatic equilibrium
When the outwards pressure from the temperature equals the inwards pressure from gravity
What happens to an average size main sequence star
After running out of hydrogen, it becomes a red giant. The star starts collapsing, so higher elements e.g. helium can fuse.
What happens to an average size red giant
Eventually when too much iron has been fused in the core, the star collapses and explodes. This outer explosion of dust forms around the white dwarf core, making it a planetary nebula
What happens to
What happens to a planetary nebula
The gas around the white dwarf core eventually disperses, leaving behind a white dwarf
What happens to a white dwarf
It cools and becomes a black dwarf (the universe isn’t old enough for this to have happened yet though)
What happens to a massive star after the nebula stage
It becomes a main sequence star
What happens to a massive main sequence star
It becomes a red super giant
What happens to a red super giant
It becomes a supernova - an extremely powerful and bright explosion
What happens to the most massive supernovas
It becomes a black hole
What happens to the normal sized supernovas
It becomes a neutron star - a star made of neutrons which ejects powerful jets of matter
Is a planetary nebula for massive or normal stars
Normal
Which is for massive and which is for normal: planetary nebula, supernova
Normal - PN
Massive - supernova
What reaction type fuels a star
Fusion - two nuclei coming together to form a high mass nucleus
What conditions do fusion reactions require and why
Very high temperature and pressure, to overrule the electrostatic repulsive force
When does a star become classed ‘dead’
When it stops fusing hydrogen
