Topic 10: Space (PAPER ONE) Flashcards
What does our solar system consist of?
- Sun (our star)
- Eight planets and their natural satellites (such as our Moon)
- Dwarf planets
- Asteroids (usually found in asteroid belts)
- Comets (lumps of ice and dust orbiting the sun - highly elliptical)
Name the planets in order (closest –> furthest from sun)
Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune
(My very easy method just speeds up naming)
Geocentric Model
- Ancient Greeks suggested Sun, Moon, Planets and Stars orbited the Earth in perfect circles
- People believed this because there were no telescopes so they just saw the sun and moon travelling across the sky
- Believed until 1500s
How have ideas changed about the universe?
Geocentric –> Heliocentric –> current model where orbits are elliptical rather than circular
How was the Geocentric model proved wrong?
- Galileo looked at Jupiter through a telescope and saw how the ‘stars’ around Jupiter were carried along with the planet. - - So, not everything was in orbit around the Earth
Heliocentric Model
- Said that the Earth and all planets orbited the sun in perfect circles
Explain how and why the weight of an object differs between surface of the earth and another body in space e.g. the moon
- Gravitational field strength depends on the mass of the body creating the field
- The larger the mass of the body, the stronger its gravitational field
- SO, objects weigh more on larger bodies (e.g. weighs more on earth than the moon)
Name 2 things wrong with the Heliocentric model of our solar system
- Planets’ orbits are actually elliptical rather than circular
- Sun is not at the centre of the universe
Describe the ‘Steady State’ theory
- Says the universe has always existed and always will
- As the universe expands, new matter is constantly being created
Compared to BBT: Doesn’t give a finite age for the universe, not the current accepted theory
Describe the ‘Big Bang’ theory
- Initially, all matter in the universe occupied a very small, dense, hot space
- Then it ‘exploded’ and space started expanding
- Gives a finite age for universe (13.8 billion years)
- Currently the accepted theory
Explain Red-shift
- As an object (/star) moves away from us, the wavelength increases and the light is red-shifted (moves towards red end of the spectrum)
- This proves that the universe is expanding, and galaxies are moving away from each other
- (also known as the Doppler effect)
How are planets orbiting the sun accelerating?
- Gravitational force causes the planet to change direction constantly as it moves in a circle
- So, the velocity is always changing meaning that the planet is accelerating whilst the speed is constant
How does the speed of orbit change?
- If a planet moves closer to the sun, the gravitational force increases
- As the force increases, so does acceleration causing an increase in velocity
- So, faster moving planets need to move in a stable orbit with a smaller radius than slower ones
Name a piece of evidence that explains both the Steady State and Big Bang theories
Red-shift (universe is expanding with galaxies moving away from each other)
Name a piece of evidence that explains the BBT only
CMBR (cosmic microwave background radiation)
- Scientists have detected microwave radiation from all parts of the universe left over from the beginning (big bang)
SO, proves that the universe had a beginning
What’s a nebula?
Stars begin as a cloud of dust and gas called a NEBULA
Lifecycle of a star
Nebula
Protostar
Main sequence
———-
Red giant
White dwarf
Black dwarf
OR
Red supergiant
Supernova
Neutron star OR Black hole
Describe the formation of a red supergiant
RED SUPERGIANT formation:
- Hydrogen in main sequence star’s core begins to run out, so the force due to gravity is larger than the pressure and the star is compressed.
- It is then dense and hot enough to undergo fusion which increases thermal expansion pressure so the star expands to form red supergiant
How are protostars formed?
Formation of PROTOSTAR:
- Gravity pulls dust and gas together so it gets hot and nuclear fusion occurs which releases energy.
- So, the core of the star is hot.
- Meaning, very high temperatures and pressures are reached
Describe main sequence stars
MAIN SEQUENCE STAR:
Stable phase, the force of gravity holding the star together is balanced by higher pressure due to the high temperatures
Explain the formation of a supernova
- Red Supergiants undergo more fusion to make heavier elements
- Balance shifts between thermal expansion and gravity, so it expands and contracts
- Eventually it explodes into a supernova
How are black holes and neutron stars formed?
Neutron star: Exploding supernova throws outer layers of dust and gas into space to leave a dense core called a neutron star
Black hole: Exploded supernova could collapse and become a black hole
Describe the formation of a red giant
- Hydrogen in main sequence star’s core begins to run out, so the force due to gravity is larger than the pressure and the star is compressed.
- It is then dense and hot enough to undergo fusion which increases thermal expansion pressure so the star expands to form red supergiant
How is a white dwarf formed?
Star become unstable and ejects its outer layer of dust and gas
So, a hot, dense solid core is left behind (white dwarf)
