What is Hubble’s law?
A galaxy’s recessional velocity is directly proportional to its distance from the Earth.
v = H d
What is the Big Bang Theory?
The universe began with a huge explosion from a singularity that was infinitely small and infinitely hot.
What is Cosmological Microwave Background Radiation (CMBR)?
Red-shifted high-energy radiation everywhere that was lost energy as the universe expanded and cooled. This provides evidence for the Big Bang.
How does the relative abundance of H and He provide evidence for the Big Bang?
During the early stages of the Big Bang, nuclear fusion converted hydrogen nuclei into helium nuclei. The universe cooled too much and it stopped. Approx. 1/4 of all existing hydrogen nuclei were fused into helium, resulting in a relative abundance ratio of H:He of 3:1.
Today, 73% hydrogen, 25% helium and 2% everything else.
What is a quasar?
A supermassive black hole surrounded by a disc of matter which, as it falls into the black hole, causes jets of radiation to be emitted from the poles. They are the most distant measurable objects in the known universe.
What are exoplanets?
Planets that are not within our solar system.
What are the two methods for detecting exoplanets?
Radial velocity method, transit method
What is the radial velocity method for detecting exoplanets?
Periodic Doppler shift in light received (from star) due to star and planet orbiting common centre of mass
What is the transit method for detecting exoplanets?
If a planet crosses in front of a star, the intensity of the light output of the star dips slightly. If it dips regularly, it could be a sign of an exoplanet orbiting it.
The size and orbital period can be determined from the amount the intensity falls by and the duration of the dip.
What limits the transit method?
It only works if the line of sight to the star is in the plane of the planet’s orbit, which is more likely for planets with small orbits. This is because most orbits are inclined.
Explain what is meant by cosmological microwave background radiation and how its existence supports the Big Bang Theory.
It is the radiation coming from all parts of the universe (isotropic). When the universe cooled sufficiently for matter and radiation to ‘decouple’, protons and electrons combined to form neutral atoms. This radiation has been red-shifted into the microwave region as the universe has expanded.
Explain how the relative abundance of hydrogen and helium supports the Big Bang theory.
Fusion occurred, resulting is the production of helium from fusing hydrogen. Fusion stopped as the universe then expanded and cooled, resulting in a relative abundance of hydrogen and helium in the ration 3:1.
Compare the use of a CCD with the use of the naked eye to observe binary stars (only need one of the ones listed but try to know them all)
- CCD has better resolution due to having smaller pixels so the stars could be more easily seen as separate
- CCDs have higher quantum efficiency and can be exposed for a long time so dimmer/more distant stars can be observed
- CCDs can detect a wider range of wavelengths, enabling the observation of more binary pairs
What are the Balmer lines?
Hydrogen absorption lines, found in the spectra of O, B, and A stars.
What is the condition for the Balmer lines to be present?
The electron must start from n=2.
Why are the Balmer lines not present if the star is too hot?
Hydrogen atoms within excited to higher levels than n=2, so hydrogen Balmer lines are not present (has to start from n=2).
Why are the Balmer lines not present if the star is too cold?
The hydrogen atoms won’t be excited at all, and they need to be at n=2.
What is the property of quasars that led to their discovery?
High power radio emitter
What is the formula for brightness ratio?
2.51^(m2 - m1)
What is the defining property of a black hole?
A black hole is an object with an escape velocity greater than the speed of light.
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Metric Prefixes9
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Particles31
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Particle physics flashcards (not the big grid of facts)42
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optical fibres11
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Nuclear and radioactivity48
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Thermal19
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Gravitational fields31
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Electric fields15
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Capacitors11
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Astrophysics89
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Mechanics and materials3
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Waves1
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Magnetic fields62
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telescopes40
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classification of stars28
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cosmology20
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lifecycle of low mass star7
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lifecycle of medium mass star3
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lifecycle of a stupidly ginormous star3
