Yr 13 - Astrophysics & Cosmology (5.5.1 & 5.5.2) Flashcards
Planet
A large mass
- No fusion
- Orbits a star
- Has cleared its orbit of most objects
Galaxy
Huge collection of gas, dust and billions of stars including their planetary systems.
Star
Luminous ball of held together by its own gravity.
Planetary Satellites
Naturally or man-made bodies that orbit planets
Comet
Small irregular balls of dust, ice and rock.
- Highly elliptical orbits
Terrestrial Planet
Planet with a hard surface (Rock or Metal).
Nuclear fusion
The process of 2 nuclei joining together & releasing energy from a change in binding energy.
Binding Energy
Energy required to separate particles.
Universe
All of space & time and their contents.
Gravitational Collapse
Inward movement of material in a star due to the gravitational force caused by its mass.
- Occurs in mature stars when internal gas and radiation pressure can no longer support its mass.
Radiation Pressure
Pressure due to the momentum of photons released in fusion reactions.
- Acts outward in direction of energy flow
Gas Pressure
Average linear momentum of gas particles.
Main Sequence Star
Any star that fits the L - T relationship (L ∝ 1 / T )
Red Giant
Star in later stage of its life that has nearly exhausted the hydrogen in its core
- Larger than normal star due to surface layers cooling and expanding.
Planetary Nebula
Expanding, glowing shell of ionised hydrogen and helium ejected from a red giant star at the end of its life.
Electron degeneracy pressure
Pressure that stops the gravitational collapse of a low-mass star.
- Pressure that prevents a white dwarf star from collapsing.
A quick way to think about this is by imagining a tube of tennis balls, in which each tennis ball represents an electron. The tennis balls can only sit one on top of each other in the tube; there is not enough space in the tube for two tennis balls to be at the same level. If you try and push a tennis ball down onto another tennis ball, there is a resistive force that pushes back upwards. This is (somewhat) similar to the how the electron degeneracy pressure works.
Chandrasekhar limit
Maximum possible mass for a stable white dwarf star (1.4 solar masses).
- White dwarfs with greater masses collapse further to become neutron stars or black holes.
Chand - ra - se - kar
Red super giant
Star that has exhausted all the hydrogen in its core and has a mass much greater than the sun.
Supernova
Huge explosion produced when the core of a red super giant collapses.
Neutron star
Remains of the core of a red super giant after it has undergone a supernova explosion.
- Incredibly dense and composed of mostly neutrons.
Black Hole
Core of a massive star that has collapsed almost to a point.
- Very dense and small.
- Gravitational field so strong that light cannot escape.
-Escape Velocity greater than speed of light.
Escape Velocity
Minimum Velocity an object must have to escape a gravitational field.
What does a Hertzsprung-Russell (HR) Diagram show & describe what it looks like & where certain stars will be.
Graph showing the relationship of a stars Luminosity & Temperature.
- Stretched S shape from top left to bottom right
- White Dwarf bottom left
- Red giant just NE of SOL
- Supergiants top right
- SOL midway through S shape
- S shape is main sequence
- Cold to hot on x axis
Luminosity
Total energy emitted by a star per second.
Protostar / Stellar Nebula
Hot dense sphere of dust & gas that could become a star.
- Not all protostars start nuclear fusion
Explain what happens when a star has a mass less than the Chandrasekhar limit
- Moves off Main Sequence
- Becomes Red Giant
- Planetary Nebula
- White Dwarf
Explain what happens when a star has a mass more than the Chandrasekhar limit
- Moves of Main Sequence
- Becomes Red Super Giant
- Supernova
- Black Hole or Neutron Star
Lifecycle for Large Star
- Stellar Nebula
- Massive Star
- Super Red Giant
- Supernova
- Black Hole OR Neutron Star
Lifecycle for average/small star
- Stellar Nebula
- Protostar (nebula comes together into tight mass of hydrogen, gas and dust)
-Average Star (protons begin nuclear fusion due to high pressure and temp) - Red Giant
- Planetary Nebula
- White Dwarf
Nebula
collection of hydrogen dust and gas
- Comes together due to gravity
- Forms stars
Solar System
Collective name for star & all objects orbiting it.
what causes the outward & inward force on a star?
Fusion reactions - Outward
Gravity - Inward
