Astronomy - topic 6 Flashcards
what are planets
large objects which orbit a star
what are dwarf planets
similar to planets but too small
what are satellites
objects that orbit a second more massive object
what are asteroids
lumps of rock and metal that orbit the sun
what are comets
lumps of ice and dust that orbit the sun
why do objects travelling in a circle not have constant velocity
velocity is speed with direction, and direction is always changing when moving in a circle and so velocity can’t stay the same
planets closest to the sun
mercury
venus
earth
mars
jupiter
saturn
uranus
neptune
what is the orbit of a comet
elliptical
what is the orbit of planets and satellites
almost circular
what are optical telescopes used for
detecting other parts of the EM spectrum
what are telescoped used for
to see distant objects clearly and to observe the universe
what does a larger aperture mean
better image quality
why are telescopes better on mountains
less light and air pollution
geocentric model
earth is at the centre of solar system and everything orbits the Earth in perfect circles
why was the geocentric model at the time was accepted
people didn’t have telescopes so they had to use the naked eye and they saw the sun and moon travelling across the sky in the same direction
what was the heliocentric model
the idea that the sun is at the centre of the universe and everything orbits the sun in perfect circles
what was the evidence disproving the geocentric model
Galileo, while looking at Jupiter saw stars near the planets, and the stars never moved away but along with the planet. This shows not everything moved around the Earth
why are bigger telescoped better
better resolution and they can gather more light so we can see things we previously couldnt and better magnification
what is the doppler effect
change in frequency and wavelength. This happens because the waves bunch together in front of the source and stretch out behind it
what is red shift
when we look at light from many distant galaxies we find that its wavelength is longer than it should be and the light we detect is shifted towards the red end of the visible spectrum
what does red shift show us
the galaxy the light came from is moving away from Earth and that the universe is expanding
the faster the galaxy moves away from us …….
the larger the red shift
how can you measure the red shift
looking at absorption spectra
what is CMBR
radiation left over from an initial explosion that has cooled over time
what are the 2 theories of the origin of the universe
steady state theory and big bang theory
what doe steady state theory say
universe has no beginning and it has always existed as it is now and the universe is expanding
what does big bang theory say
all galaxies are moving away from each other and universe was created from a small point with all the matter in the universe exploding and then expanding
evidence for big bang theory
CMBR and red shift
evidence for steady state theory
red shift
what is a nebula
a cloud of dust and gas
life cycle of an average star
nebula
protostar
average star
red giant
planetary nebula
white dwarf
life cycle of a massive star
nebula
protostar
massive star
red supergiant
supernova
neutron star or black hole
what does the solar system consist of
the Sun, eight planets and their natural satellites, dwarf planets, asteroids and comets
what is the orbit of planets like
almost circular orbits
what is the orbit of moons like
circular orbits
what is the orbit of artificial satellites
almost circular orbits
what is the orbit of comets like
highly elliptical
why does the radius of the orbit of an object in a stable orbit changes size if the speed of the object changes
if the object moves faster, the radius of its orbit must be smaller
what is a nebula
a cloud of dust and gas
how is a protostar formed
the attractive force of gravity pulls dust and gas together to form a protostar
how is a star(main sequence) formed
A nebula is a cloud of dust and gas
gravitational attraction causes the density of the protostar to increase as particles within the protostar to collide with each other more frequently so the temperature increases
When the temperature gets hot enough, nuclear fusion occurs, forming a hydrogen nuclei in the core of the star.
lots of energy is given out, which keeps the core of the star hot.
A star is made
how is a red giant formed
eventually, the hydrogen in the core begins to run out and the force due to gravity is larger than the pressure of thermal expansion.
The star is compressed, until it is dense and hot enough that the energy created makes the outer layers expand.
The star becomes a red when the surface cools
what two forces are balanced in the main sequence stage of a stars life
gravity and thermal pressure. Gravity is pushing inwards and thermal pressure is pushing outwards
what happens to a star if the gravity acting on it is larger than thermal pressure
it will turn into a black hole
how are white dwarfs formed
When a red dwarf becomes unstable and ejects its outer layer of dust and gas as a planetary nebula and this leaves behind a hot, dense solid core - a white dwarf
what is the evolution of stars with a mass larger than the sun
stars will expand into red super giants when they start to run out of hydrogen
eventually, they become unstable as they run out of elements to fuse and they explode into a supernova, forming elements heavier than iron and eject them into the universe
the exploding supernova throws the outer layer of dust and gas into space, leaving a neutron star
If the star is big enough, it will become a black hole instead
how have methods of observing the universe changed over time
the earliest telescope was the optical telescope, then telescopes were developed to detect other parts of the EM spectrum so we can learn and see more about the universe
how have telescopes improved
They are bigger, so they have a better resolution and can gather more light and there is improved magnification
why do modern telescoped work alongside computers
computers help create clearer and sharper images and make it easy to capture these pictures so they can be analysed later
how does lens affect image quality
using a larger aperture or higher quality lens will improve the image quality
why are some telescopes placed outside the Earth’s atmosphere
to observe the frequencies absorbed as the Earth’s atmosphere absorbs a lot of the EM radiation coming from space before it can reach the telescopes on earth
AND
on earth there is light and air pollution
what is the doppler effect
as a police car moves towards you its siren sounds higher pitched than it would if it were stationary. As it moves away from you its pitch is lower. This change in frequency and wavelength is the doppler effect
what is red shift
when we look at light from many distant galaxies we find its wavelength is longer than it should be. The light we detect is shifted towards the red end of the visible spectrum, it is redder than the actual light emitted by the galaxy
why does red shift of galaxies provide evidence for the universe expanding
it shows us that the galaxy that the light came from is moving away from the earth.
what is CMBR
cosmic microwave background radiation is radiation that comes from all parts of the universe
what is steady state theory
it says the universe has no beginning and no end, it has always existed as it is now, and it always will and as the universe expands, new matter is constantly created
what is the big bang theory
the theory says that initially all matter in the universe was occupied in a very dense and hot small space and it exploded. Then, space started expanding and is still expanding
how old does the big bang theory day the universe is
around 13.8 billion years
what is the evidence supporting the steady state theory
red shift
what is the evidence supporting the big bang theory
CMBR and red shift
how is red shift used as evidence for both theories
both theories state the universe is constantly expanding
how is CMBR used as evidence for the big bang theory
CMBR is left over energy from an initial energy from an initial explosion that has cooled over time which suggest the universe has a beginning
why is the big bang theory the currently accepted model of how the universe began
there is more evidence supporting the Big Bang theory than the steady state theory
