Topic 7 - astronomy Flashcards
Explain the composition of our solar system
our Solar System consists of the Sun (our star), eight planets and their natural satellites (such as our Moon); dwarf planets; asteroids and comets
Describe the eight planets in order (distance from the sun) and other elements in our solar system
Closest
Mercury Venus Earth (has one natural satellite called the moon. Larger planets such as Jupiter and Saturn have many natural satellites or moons) Mars Jupiter Saturn Uranus Neptune
Furthest
Most asteroids form a ring of rocks that orbits the sun and is found between mars and Jupiter. Comets travel in highly elliptical paths and come from many millions of miles away
Describe how ideas about the structure of the Solar System have changed over time
Many early people thought that the sun and all planets moved around the earth (geocentric) In about 130 CE this was published by Ptolemy (a Greek philosopher)
However in 1543 Nicolaus Copernicus argued that the earth and planets were in orbits around the sun. This is HELIOCENTRIC (sun centred)
Describe the orbits of moons, planets, comets and artificial satellites
NATURAL satellites were formed by natural processes ( the eight planet - orbit the sun, the moons - orbit the planets, and comets - orbit the sun sun )
ARTIFICIAL SATELLITES are manufactured and were launched by rockets into space. Examples include:
- satellites in GEOSTATIONARY orbits around the earth being used for global positioning satellite systems (GPS)
- satellites in LOW POLAR ORBITS around the earth being used for weather monitoring, military, spying or earth observation purposes
- satellites SENT FROM EARTH to orbit and monitor the sun, other planets or asteroids in the solar system
Explain for circular orbits how the force of gravity can lead to changing velocity of a planet but unchanged speed
The gravitational force acting on a body in a circular orbit will be the same at each point of the orbit, since the radius is fixed.
The speed of the orbit will not change, but the velocity will be constantly changing because the direction is constantly changing.
Explain how, for a stable orbit, the radius must change if orbital speed changes
The planets in our solar system are in stable orbits. For example:
- If the earths orbital speed increased then the gravitational force from the sun wouldn’t keep it in orbit. It would fly out of its orbit, into a new orbit of greater radius.
- If the earths orbital speed decreased, the suns gravitational field would cause it to fall towards it, into a new orbit of smaller radius
Compare the Steady State and Big Bang theories
The Big Bang theory says the whole universe started out as a tiny particle about 13.8 billion years ago. The universe expanded from this point in space. The universe is still expanding today.
However the steady state theory says that the universe has always existed. It is expanding, and new matter is being created as it expands.
Explain how red shift supports the big bang theory
RED SHIFT is when objects emit light when they are moving away from us, this light emitted is ‘red-shifted’. This means that the wavelengths from them when detected back will be ‘stretched’. The spectral lines will be shifted further to the red end of the spectrum.
The faster a galaxy is moving away from us , the more these lines will be shifted to the red end of the spectrum. Since the furthest galaxies show more red shift than those nearer to us, this suggests that the universe is expanding .
Explain how CMB supports the Big Bang theory
The cosmic background radiation (cmb) is the ‘echo’ of the Big Bang. At the time of the Big Bang this radiation would’ve been incredibly hot and intense however over time this has cooled and is now very weak at a temperature of -270 degrees close to absolute zero.
The fact that CMBR is detected in all directions and has the temperature that is does, is evidence that the universe started with a Big Bang almost 14 billion years ago
Describe the cosmic microwave background radiation (cmb or cmbr) and explain why the Big Bang theory is currently the accepted model for the beginning of the universe
(4 marks)
The cosmic background radiation is detected by radio telescopes and comes from all over the sky. The Big Bang theory says that this radiation was released at the beginning of the universe.
Red shift supports both theories but the CMB only supports the Big Bang theory. The Big Bang theory is accepted because there is more evidence for it. CMB is key to supporting the Big Bang theory.
Explain what the Doppler effect is
When a wave source is moving relative to an observer, there is a change in the observed frequency and wavelength of the waves.
Explain the relationship between red shift and the Doppler effect
The Doppler effect occurs for light waves as well as for sound waves.
A light source moving away from an observer will have a GREATER WAVELENGTH and a LOWER FREQUENCY. It is ‘red shifted’.
A light source moving towards an observer will have a SMALLER WAVELENGTH and a HIGHER FREQUENCY. It is ‘blue-shifted’
Explain why the red-shift of galaxies provides evidence for the Universe expanding
In 1929, the astronomer Edwin Hubble discovered that the light reaching earth from galaxies was red shifted. He found this out by looking at the spectral lines in the absorption spectra of stars that are moving away from us.
