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Physics module 5 > Astrophysics and Cosmology > Flashcards

Astrophysics and Cosmology Flashcards

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1
Q

Nuclear fusion

A

The process of two nuclei joining together and releasing energy from a change in binding energy

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2
Q

Galaxy

A

A cluster of millions or billions of stars

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3
Q

Stars

A

Are formed when huge amounts of matter, gas or interstellar dust are pulled together under the force of gravity

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4
Q

Planet

A

Bodies that move in elliptical orbits around stars to form a solar system

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5
Q

Planetary satellites

A

Smaller bodies than planets can orbit them, these bodies are called planetary satellites. An example is the moon

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6
Q

Gravitational collapse

A

The inward movement of material in a star due to the gravitational force caused by its own mass

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7
Q

Radiation pressure

A

Due to the momentum or photons released in fusion reactions

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8
Q

Gas pressure p

A

Is related to temperature and volume using pV =nRT

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9
Q

A main sequence star

A

A star in the main part of its life cycle, where it is fusing hydrogen to form helium in its core

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10
Q

A red giant

A

A star in the later stages of its life that has nearly exhausted the hydrogen in its core and is fusing helium nuclei.

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11
Q

A white dwarf

A

The end product of a low mass star. Very dense with a high surface temperature and low luminosity

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12
Q

Planetary nebula

A

An expanding, glowing shell of ionised hydrogen and helium ejected from a red giant star at the end of its life

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13
Q

Electron degeneracy pressure

A

The pressure that stops the collapse of a low mass star, this prevents a white dwarf from collapsing

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14
Q

Chandrasekhar limit

A

The maximum possible mass for a stable white dwarf star. It is equal to 1.4 times the mass of our sun. White dwarfs above this mass will collapse further to become neutron stars or black holes

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15
Q

Luminosity

A

The total energy emitted per second

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16
Q

Hertzsprung-Russell diagram

A

A luminosity-temperature graph

17
Q

Supernova

A

The huge release of energy

18
Q

Wien’s displacement law

A

λmax *T = constant. It is used to estimate the peak surface temperature of a star from the wavelength at which the stars brightness is maximum

19
Q

Stefans law

A

Relates the luminosity of a star with its absolute temperature
T = 4πr^2σT^4

20
Q

Astronomical unit (AU)

A

The mean distance from the centre of the Earth to the centre of the Sun

21
Q

The parsec

A

A unit of distance that gives a parallax angle of 1 second of arc (1/3600 of a degree)

22
Q

Stellar parallax

A

The apparent shifting of a star viewed against a background of distant stars when viewed from different positions of Earths orbit

23
Q

Doppler effect

A

The change in wavelength caused by the relative motion between the wave source and an observer
Δλ/λ=Δf/f = v/c

24
Q

Red shift

A

The apparent increase in wavelength of electromagnetic radiation caused when the source is moving away from the observer

25
Q

Blue shift

A

The apparent decrease in λ of electromagnetic radiation caused when the source is moving towards the observer

26
Q

Hubbles law

A

The recessional velocity of a galaxy is directly proportional to its distance from Earth

27
Q

Hubble constant

A

The constant of proportionality in v =H.d

28
Q

Cosmic background radiation

A

Microwave radiation received from all over the smh originating from after the Big Bang, when the universe cooled to 3000K. As the universe expanded, this is now just a faint microwave

29
Q

The Big Bang theory

A

The universe started as an infinitely small, dense and hot point then expanded to what it is now. Time and space were both created at the instant of the Big Bang

30
Q

The cosmological principle

A

The universe is:
•isotropic (The same in all directions)
•homogenous (of uniform density)
•subject to the same physical laws everywhere

31
Q

Dark matter

A

Matter that cannot be seen and that does not emit or absorb electromagnetic radiation.
We know of its existence because of the expected mass of galaxies being so small compared to the actual

32
Q

Dark energy

A

A type of energy that permeates the whole universe and opposes the attractive force of gravitation between galaxies via the exertion of negative pressure.
We predicted its existence because of the accelerating expansion of the universe opposing gravity

Physics module 5 (6 decks)

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