Astrophysics Flashcards
what is the universe
the universe is a large collection of billions of galaxies
what are galaxies
a galaxy is a large collection of billions of stars
what galaxy is our solar system in
the milky way galaxy
what are the planets
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune
My Very Educated Mother Just Served Us Noodles.
define weight
The force acting on an object due to gravitational attraction
asteroids vs comets
asteroids are lumps of rock and metal which orbit the sun
comet are lumps of ice and dust which orbit the sun
universe vs galaxy
A galaxy is a large collection of stars,
whereas the Universe is made up of billions of galaxies.
what is the milky way
The Milky Way is a galaxy containing billions of stars, including our Sun.
what do weight and GFS vary on
The greater the mass of the planet then the greater its gravitational field strength
A higher gravitational field strength means a larger attractive force towards the centre of that planet or moon
state what these object orbit around
planet
moon
comet
asteroid
artificial satalites
planet - sun
moon - planet
comet - sun
asteroid - sun
artificial satalites - earth
how can we describe why things orbit the way they do
Smaller bodies orbit around larger bodies
what is orbital motion
Orbital motion is a result of the gravitational force of attraction acting between two bodies
what does the gravitational force in an orbital motion always do
(and causes what)
always acts towards the centre of the larger body
causes the orbiting body to move in a circular path
similarites of planet which orbit the sun
Their orbits are all slightly elliptical (stretched circles) with the Sun at one focus (approximately the centre of the orbit)
They all orbit in the same plane
They all travel in the same direction around the Sun
differences of planet which orbit the sun
They orbit at different distances from the Sun (different orbital radius)
They orbit at different speeds
They all take different amounts of time to orbit the Sun
what does the distance from the sun have to do with the way the planet orbits it
The further away a planet is from the Sun, the slower it travels and therefore the longer it takes to orbit
what is the orbital motion of the moon
Moons orbit planets in a circular path
Some planets have more than one moon
The closer the moon is to the planet:
- the shorter the time it will take to complete each orbit
- the greater the speed of the orbit
what is the orbital motion of comets
The orbits of comets are very different to those of planets:
Their orbits are highly elliptical (very stretched)
This causes the speed of the comets to change significantly as their distance from the Sun changes
Not all comets orbit in the same plane as the planets and some don’t even orbit in the same direction
- As the comet approaches the sun, its speed increases
- As it moves further away from the sun, its speed decreases
what is orbital period
The time taken for an object to complete one orbit
how are stars classified
their color because the colour they emit depends on how hot they are
relation of temp and color with a star
the HOTTER star will be blue
the COOLER star will be red
what happens to stars as they change
When a star becomes a red giant it becomes redder as it expands and cools
When a star becomes a white dwarf it becomes whiter as it contracts and heats up
life cycle of a LOW mass star
nebula
gravitational collapse
main sequence star
red giant
planatary nebula
white dwarf
life cycle of a HIGH mass star
nebula
gravitational collapse
main sequence star
super red giant
super nove
either:
- neutron star
- black hole
what is a nebula
giant interstellar cloud of gas and dust
what does a stars brightness depend on
the luminosity
the distance of the star from earth
what is luminosity
The total amount of light energy emitted by the star
Luminosity is a measure of a star’s brightness or power output
what is apparent magnitude
The perceived brightness of a star as seen from Earth
what is absolute magnitude
A measure of how bright stars would appear if they were all placed the same distance away from the Earth
what is a Hertzsprung-Russell diagram
and how are stars ordered
This is a plot of luminosity on the y-axis and temperature on the x-axis
For stars which are brighter than the Sun, luminosity > 1
For stars which are dimmer than the Sun, luminosity < 1
state the 4 areas
A, B, C, D
A = white dwarf stars
B = main sequence stars
C = red supergiant stars
D = red giant stars
describe key areas of a HR diagram
The brightest stars (high luminosity) are found near the top
The dimmest stars (low luminosity) are found near the bottom
The hottest stars (high temperature) are found towards the left
The coolest stars (low temperature) are found towards the right
what is the big bang theory
Around 14 billion years ago, the Universe began from a very small region that was extremely hot and dense
Then there was a giant explosion, which is known as the Big Bang
what are the 2 main peices of evidence for the big bang
Galactic red-shift
Cosmic Microwave Background (CMB) radiation
what is evidence that the universe is shifting
redshift in the light from distant galaxies
What conclusions have astronomers made from these red shift observations
All galaxies are moving away from the Earth.
Galaxies are moving away from each other.
This expansion is expected after an explosion.
How does matter behave after an explosion?
Matter starts densely packed and moves outward in all directions.
Lighter matter moves faster and travels further.
Heavier matter moves slower and stays closer to the source.
How is the distance of a galaxy related to its speed?
The further a galaxy is, the faster it moves. The closer a galaxy is, the slower it moves.
What is Cosmic Microwave Background (CMB) radiation
It is a type of electromagnetic radiation that is a remnant from the early stages of the Universe.
Why is CMB classified as microwave radiation
It has a wavelength of around 1 mm, placing it in the microwave region of the electromagnetic spectrum.
What does the Big Bang theory say about the early Universe
The early Universe was extremely hot and dense, meaning it must have emitted thermal radiation.
How has the wavelength of the CMB radiation changed over time
As the Universe expanded, the wavelength increased, shifting it into the microwave region.
what does CMB’s pattern suggest
The CMB radiation is very uniform and has the exact profile expected to be emitted from a hot body that has cooled down over a very long time
what can we use the doppler shift for
The doppler shift equation can be used to calculate the velocity of a galaxy if its wavelength can be measured and compared to a reference wavelength
What happens to the observed frequency and wavelength when a wave source moves relative to an observer
If the wave source moves toward the observer:
Frequency increases ( blue shift for light).
Wavelength decreases (waves are compressed).
If the wave source moves away from the observer:
Frequency decreases (red shift for light).
Wavelength increases (waves are stretched).
what is a redshift
The phenomenon of the wavelength of light appearing to increase when the source moves away from an observer
How does the red-shift of galaxies provide evidence for the expansion of the universe?
Red-shift shows that galaxies are moving away from Earth.
The greater the distance, the faster the galaxy moves away (Hubble’s Law).
This supports the Big Bang Theory, which suggests the universe began from a single point and has been expanding ever since.
