Space Physics Flashcards
Define solar system
A system of celestial bodies including:
- a star,
- planets,
- other bodies that orbit the star and
- moons that orbit the planets
What is a celestial body? (2)
- Any naturally occurring object
- outside of the Earth’s atmosphere
What path does a celestial body follow as it travels around another?
Orbit (circular motion)
What is the sun
The star at the centre of our solar system that has a
large enough gravitational field to keep:
- planets,
- dwarf planets,
- asteroids and
- comets
in orbit around it
What is a gravitational field?
The region of space around an object with mass in which another object with mass experiences a non-contact force
What is a planet?
A large, spherical body in space that orbits a star
What conditions are required for a planet to form? (2)
gravity must be strong enough to:
- make it spherical
- Clear its orbital path by putting other objects in its orbit
What planets are in our solar system? (In order from sun)
- mercury
- venus
- earth
- mars
- Jupiter
- Saturn
- Uranus
- Neptune
What is a dwarf planet? (2)
- A small spherical body that orbits a star
- but its orbital path is not clear of other objects
What is a satellite?
A natural or artificial body that orbits a planet
What is a moon?
A natural satellite of a planet
What is an asteroid?
A small body of rock orbiting a star
What is the asteroid belt?
The region of the solar system between orbits of Mars and Jupiter where many asteroids are found
What is a comet?
A small body of ice, rock and dust that follows a highly elliptical orbital path around a star
(orbital path = Oval type shape, close to the sun in parts, far away in others)
What is contained within a comet’s tail?
When is this produced?
- Gas and dust,
- as it passes close to a star and points away from the star
What is a Lightyear (ly)?
The distance light travels in one year
What distance does 1 ly equal?
9.46 x 1015 metres
What is a nebula?
A large cloud of dust and gas in space
How is a protostar formed?
When the core of a nebula collapses under its own gravity
When does nuclear fusion begin in the formation of stars
When the core of a protostar becomes hot and dense enough for fusion to start
What is a main sequence star?
A star that is in equilibrium and remains in this phase for most of its lifetime
What forces act on a star in equilibrium? (2)
- gravity
- thermal expansion / radiation pressure
What type of star is the sun
and
at what stage of life is it?
- a relatively small, main sequence star
- roughly in the middle of its life cycle
When is a red giant formed? (2)
- when a star about the size of the sun runs out of hydrogen
- so larger nuclei form and the star expands
When is a white dwarf formed? (2)
- When the nuclear reactions in a red giant stop
- and it starts to contract due to its own gravity
When is a black dwarf formed?
When a white dwarf cools until it no longer emits radiation
When is a red super giant formed? (2)
- When a star much larger than the sun runs out of hydrogen
- so larger nuclei form and the star expands
What is a supernova?
When does a supernova occur?
What happens after a supernova?
(4)
- When a red supergiant expands until it explodes,
- throwing hot gas into space from their outer layers
- the star shines for a relatively short time - brightness of 10 bn suns
- the remaining core may collapse more, some may become neutron stars, larger ones become black holes
What is left after a supernova?
What does this depend on?
- A neutron star or a black hole
- depending on mass of the star at the start of its life (black hole = higher mass)
Where do all naturally occurring elements come from?
Fusion reactions in stars
Where do lighter elements (up to iron) form?
How?
- main sequence stars
- when hydrogen runs out, so helium nuclei start to fuse etc.
How do heavier elements (heavier than iron) form?
When a supernova explodes, throwing the elements into the universe
What is a galaxy?
a collection of stars (held by
gravitational forces)
Which galaxy do we live in?
The Milky Way
How do astronomers investigate the composition of a planet’s atmosphere?
By observing light passing through or from a planets atmosphere - spectra
What is red shift?
What is this used as evidence for?
- When light from other galaxies is shifted to the red end of the spectrum
- This can be explained as the universe expanding - backing up the Big Bang theory
What does a red shift tell us?
The space between the Earth and distant galaxies is expanding
What is the relationship between amount of red shift and speed of galaxies? (2)
- The more the light from a distant galaxy is red-shifted,
- the faster the galaxy is moving away from earth
How did red shift lead to the development of the Big Bang Theory?
- the further away a galaxy is, the more its light is red-shifted
- which suggests the Universe is and has been expanding since creation
What is the Big Bang Theory used to describe?
The early stages of the Universe
When did the Big Bang occur?
14 billion years ago
What is CMBR (Cosmic Microwave Background Radiation)?
The remains of the heat energy released from the Big Bang which is now spread thinly across the whole Universe
How does CMBR provide evidence for the Big Bang theory?
Microwave radiation has been found from all directions in space
What is gravity needed for?
To maintain a stable orbit of planets around a star and satellites around a planet
What is an artificial satellite?
A man-made object that orbits a planet e.g. telecom satellites
What is meant by the stable orbit of a satellite? (2)
- When the speed of a satellite is slow enough to stop it flying into space
- but fast enough to stop it falling towards the planet
What is the problem when a satellite is traveling too quickly? (2)
- Gravitational attraction between planet and satellite too weak
- satellite flies into space
What is the problem when a satellite is traveling too slowly? (2)
- Gravitational attraction between planet and satellite too strong
- satellite falls toward planet
What is a geostationary satellite?
How long does it take to orbit the Earth?
- A satellite that orbits the Earth at the same rate as the Earth rotates
- 24 hours
What is the position of a geostationary satellite relative to the Earth’s surface?
It remains above the same place on the Earth’s surface
What is circular motion?
When an object follows a circular path, usually at a constant speed
What happens to velocity in circular motion?
It is changing, even if the speed is constant due to direction changes
What happens to acceleration in circular motion?
Is is accelerating because it’s direction (and velocity) is changing
What is a centripetal force?
In what direction does it act?
- The resultant force that causes the acceleration of an object traveling in a circle
- towards the centre of a circle
What does gravitational attraction provide for solar systems?
A centripetal force which keeps satellites in orbit around planets and planets in orbit around stars
How does the force of gravity between two objects vary with distance?
The closer the objects are, the stronger the force of gravity between them
(or vice-versa)
What is the effect of the magnitude of gravitational force on velocity? (3)
- Greater force of gravity
- greater acceleration
- therefore greater velocity
What is the effect of orbit size on the speed of a satellite?
Objects in small orbits travel faster than objects in large orbits
What is polar orbit?
Orbit over a planet’s poles
How long does a satellite in geostationary orbit take to complete one orbit?
24 hours
At which height above the Earth does a satellite need to be at for geostationary orbit?
Around 36 000 km above sea level
What is the relationship between orbital speed of a satellite and its height above a planet?
- further from planet’s surface
- slower it travels
What is the relationship between orbital speed of a planet and its distance from the sun?
- further from the sun
- slower it travels
Outline the stages in the life cycle of a small star - in order (6)
- nebula
- protostar
- main sequence star
- red giant
- white dwarf
- black dwarf
What observation allows astronomers to state that space is expanding?
Red shift
Outline the Big Bang Theory - in order (4)
- expansion & cooling of the universe
- neutrons & protons form
- further expansion and cooling allowed nuclei to form
- temperature drops & hydrogen atoms form from neutrons and protons combining
Why is travel to exoplanets not possible using modern technology
The journey is too slow - longer than a human life
What are exoplanets
Planets outside of our solar system
Why do black holes appear to absorb light? (2)
- there is a strong gravitational field in a black hole that nothing can escape from ,
- including electromagnetic radiation such as light
Outline the stages in the life cycle of a large star - in order (6)
- nebula
- protostar
- main sequence star
- red supergiant
- supernova
- neutron star / black hole
In what type of orbit are:
- telecom satellites
- weather satellites
- earth observation satellites
- geostationary
- polar
- polar
What temp is CMBR?
~ -270ºC
