Space Physics Flashcards
Give the Names of the Planets in Order from the Sun
Inner Planets:
-Mercury
-Venus
-Earth
-Mars
The Asteroid Belt
Outer Planets:
-Jupiter
-Saturn
-Neptune
-Uranus
Describe the Properties of the Inner and Outer Planets
Inner Planets:
-Rocky
-Hotter
-Shorter Orbits
Outer Planets:
-Gas (or Ice)
-Colder
-Longer Orbits
For a planet to form, its own gravity must be strong enough to make it round or spherical in shape. Its gravitational field must also be strong enough to ‘clear the neighbourhood’, pulling smaller nearby objects into its orbit.
Explain why Most Diagrams of the Solar System are Not to Scale
-Diagrams are not to scale because the distances between the planets is enormous.
-For example, Jupiter is 5x further from the Sun than the Earth and Neptune is 30x further than the Earth.
Give the Location and Main Characteristic of Dwarf Planets
-The dwarf planets are found beyond the orbit of Neptune.
-The gravitational field of a dwarf planet is not strong enough to clear the neighbourhood, so there may be other objects in its orbit around the Sun.
Describe what is Meant by a Moon
A moon is a natural satellite in orbit around a planet.
Describe what is Meant by an Asteroid, Comet and Meteorite
-Asteroids are large pieces of rock often found in the asteroid belt. They orbit the Sun in highly elliptical orbits, which may take years to complete.
-Comets are similar to asteroids are made of rocky material, dust and ice. As a comet approaches the Sun, it begins to
vaporise. It then produces a distinctive tail.
-Meteoroids are small pieces of rock which may fall to Earth
Describe what is Meant by a Galaxy
-A galaxy is a massive group of stars.
-For example, the Milky Way contains hundreds of billions of stars, grouped together in a spiral shape.
-There are hundreds of billions of different galaxies in the Universe.
Describe how a Star is Formed
-Stars are formed from a large cloud of gas and dust called a nebula.
-The force of gravity causes the nebula to collapse inwards.
As the nebula collapses it becomes denser, and rotates more rapidly.
-Collisions between particles cause kinetic energy to be transferred as thermal energy so the temperature increases. The core of the nebula then forms a hot, dense protostar.
-When the protostar’s core becomes hot enough and dense enough, nuclear fusion reactions begin. This releases huge amounts of energy keeping the core hot- a star is formed.
Describe the Forces Acting on a Star
-One force is gravity acting inwards.
-The other is the expansion force due to fusion energy acting outwards.
-When these are balanced the star is in equilibrium.
Describe the Lifecycle of a Star the Same Size as the Sun
-In the main sequence, a star carries out nuclear fusion. The inward force of gravity is balanced by the outward forces due to fusion energy. The star is in equilibrium.
-At some point, the hydrogen starts to run out. Now the outward forces due to fusion energy are less than the inward force of gravity. The star collapses inwards.
-As the star collapses, the temperature of the star increases. Now the star fuses together helium nuclei to form heavier elements. The star now expands to form a red giant. At some point, the star cannot fuse helium and starts to shrink.
-The star now forms a small body called a white dwarf. Because nuclear fusion has stopped, this gradually cools down. Eventually, the star cools completely to form a black dwarf.
Describe the Lifecycle of a Star Much Larger than the Sun
-In the main sequence, a star carries out nuclear fusion. The inward force of gravity is balanced by the outward forces due to fusion energy. The star is in equilibrium.
-At some point, the hydrogen starts to run out. Now the outward forces due to fusion energy are less than the inward force of gravity. The star collapses inwards.
-As the star collapses, the temperature of the star increases. Now the star fuses together helium nuclei to form heavier elements up to iron. The star now expands to form a red super giant.
-When the red supergiant stops carrying out nuclear fusion, the star collapses rapidly and it explodes into a supernova. In a supernova the temperatures are so high that elements heavier than iron can be produced.
-The heavy elements produced in a supernova are distributed throughout the universe as a result of
the supernova explosion. This leaves behind a neutron star or black hole.
Describe the Features of a Neutron Star and a Black Hole
-A neutron star consists of neutrons densely packed together.
-A black hole has such a large force of gravity that not even light can escape.
Describe the Difference Between Natural Satellites and Artificial Satellites
-Artificial satellites (for example those for satellite TV) are man-made and are placed in orbit by humans.
-This is not the case for natural satellites such as moons.
What is Meant by a Geostationary Satellite
-Satellites which orbit the Earth once every 24 hours are called geostationary satellites.
-These always point to the same part of the Earth.
What is Meant by a Polar Satellite
-A polar satellite is a satellite whose orbit is perpendicular or at right angles to the equator, passing over the north and south poles as it orbits the earth.
-Polar satellites revolve around the Earth in a north-south direction around the Earth as opposed to east-west like the geostationary satellites.
-They are low altitude and their period of revolution is around 100 minutes.
Explain why a Body in Orbit has a Constant Speed but Changing Velocity
-The force of gravity causes the satellite to accelerate towards the Earth.
-The acceleration causes a change in direction.
-Velocity changes because direction changes.
Describe how Gravity Keeps Bodies in Orbit
-If an object is travelling in a circle it is constantly changing direction, which means it is constantly accelerating. For an object to accelerate, there must be a force acting on it. This force is directed towards the centre of the circle.
-This force would cause the object to just fall towards whatever it is orbiting, but as the object is already moving, it just causes it to change its direction.
-The object keeps accelerating towards what it is orbiting but the instantaneous velocity (which is at a right angle to the acceleration) keeps it travelling in a circle.
-The force that makes this happen is provided by the gravitational force between the planet and the Sun (or the planet and its satellites).
Explain why the Radius of a Satellite Decreases when its Speed Increases
-When a satellite increases in speed, it requires a greater force of gravity to prevent the satellite flying off into space.
-By moving closer to the Earth (decreasing the radius), this increases the force of gravity and keeps the satellite in a stable orbit.
State the Calculation for the Speed of a Satellite
Speed = Circumference / Time for Orbit
Explain what is Meant by Red Shift
Red-shift is explained as:
-Galaxy A is moving away from us. The wavelength of light appears to have increased.
Explain how Red Shift Support the Theory of the Big Bang
-The furthest galaxies show the biggest red shift.
-This means that the furthest galaxies are moving fastest so the Universe is expanding.
-Extrapolating backwards this suggests that the Universe started from an initial point
Explain the Cause of the Dark Lines on the Spectra
-The Sun contains a large number of different elements (which are formed in the Sun due to nuclear fusion).
-These elements absorb light of specific wavelengths, causing the dark lines in the Sun’s spectrum. The lines represent wavelengths that have been absorbed.
-When light is absorbed, it causes electrons to move from one energy level to an energy level with a higher energy
Explain how the Spectrum Shift of a Dark Line Suggests the Universe Started from an Initial Point
-The line shifts towards the red end of the spectrum.
-The wavelength appears to increase.
-This suggests the galaxy is moving away from an initial point.
Give an Advantage and Disadvantage of Using a Balloon to Represent the Expanding Universe
Advantage:
-As the balloon expands the dots get further apart, representing the galaxies moving apart
Disadvantage:
-There is a limit to how far the balloon can expand
Explain what is Meant by the ‘Big Bang’
-The Big Bang theory states that the Universe began from a very small region that was extremely hot and dense.
-This small region ‘exploded’ sending matter outwards.
How do Scientists Explain the Observation that the Universe’s Expansion is Speeding Up
-Scientists have observed that the expansion of the Universe is speeding up.
-They think that this may be due to dark matter and dark energy.
-Dark matter is the name given to an unknown substance which holds galaxies together but does not emit electromagnetic radiation.
