5.5

Question 1

Nuclear fusion

Answer 1

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

Question 2

What are comets?

Answer 2

Large rocky icy balls that travel in highly elliptical orbits around the Sun

Question 3

Gravitational collapse

Answer 3

The inward movement of material in a star due to the gravitational force caused by its own mass. Star formation is due to the collapse of gas and dust

Question 4

Why does gravitational collapse occur in mature stars?

Answer 4

When the internal gas and radiation pressure can no longer support the star’s own mass it under goes collapse

Question 5

Radiation pressure

Answer 5

Due to the momentum of photons released in fusion reactions and acts outwards (in the direction of energy flow)

Question 6

Main sequence star

Answer 6

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

Question 7

Red giant

Answer 7

Star in the later stages if its life that has nearly exhausted the hydrogen in its core and is now fusing helium nuclei.
Bigger than normal star as the outer layers have cooled and expanded

Question 8

White dwarf

Answer 8

End product of a low mass star, when the outer layers have dispersed into space.
Very dense, high surface temp, low luminosity

Question 9

Planetary nebula

Answer 9

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

Question 10

Electron degeneracy pressure

Answer 10

Pressure that stops the gravitational collapse of a low mass star.
The pressure that stops a white dwarf collapsing

Question 11

Chandrasekhar limit

Answer 11

The maximum possible mass for a stable white dwarf star, is equal to 1.4 x mass of our Sun.
Higher mass white dwarfs will further collapse to neutron stars/black holes

Question 12

Red super giant

Answer 12

Star that has exhausted all the hydrogen in its core and has a mass much higher than the Sun

Question 13

Supernova

Answer 13

Huge explosion produced when the core of a red super giant collpases

Question 14

Neutron star

Answer 14

The remains of the core of a red super giant after it has undergone a supernova explosion, incredibly dense and composed mainly off neutrons

Question 15

Black hole

Answer 15

Core of a massive star that has collapsed almost to a point
Very very dense and very small
Infinite gravitational field strength
Escape velocity > speed of light

Question 16

Hertzsprung-Russel diagram

Answer 16

White dwarf: bottom left
Main sequence: diagonal line through middle (y=-x)
Nebula: bottom right
Protostar: above nebula 
Red giant: middle right
Red super giant: top right

Question 17

Luminosity

Answer 17

Total energy a star emits per second

Question 18

Continuous spectrum

Answer 18

Spectrum appears do contain all wavelengths over a comparatively wide range

Question 19

Energy levels

Answer 19

Inside an atom they are the specific energies that electrons can have when occupying specific orbits. Electrons can only occupy these discrete energy levels and cannot exist at other energy values between them

Question 20

Emission line spectrum

Answer 20

Individual elements have a spectrum of frequencies of electromagnetic radiation emitted due to electron transitions from a higher energy level to a lower one.
Bright lines against a dark background

Question 21

Absorption line spectrum

Answer 21

Pattern of dark lines in a continuous spectrum from a light source caused by light passing through an absorbing medium such as a gas.
Dark lines are wavelengths that are absorbed

Question 22

Transmission diffraction grating

Answer 22

Glass surface having a large number of very fine parallel grooves or slits, used to produce optical spectra by diffraction

Question 23

Maxima

Answer 23

Regions of brightness which will be seen when the path difference between overlapping waves is a whole number of wave lengths

Question 24

Wien’s displacement law

Answer 24

Max wavelength is inversely proportional to T

Used to estimate the peak surface temperature of a star from the wavelength at which the stars brightness is maximum

Question 25

Stefan’s law

Answer 25

L = 4πr²σT⁴

Question 26

Astronomical unit

Answer 26

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

Question 27

Parsec

Answer 27

Unit of distance that gives a parallax angle of 1 arc second (1/3600 of a degree)
Approx. 3.1*10¹⁶

Question 28

Stellar parallax

Answer 28

Apparent shifting in position of a star viewed against a background of distant stars when viewed from different positions of the Earth in its orbit of the sun

Question 29

Light year

Answer 29

Distance travelled by light in one year

Approx 9.5 x 10¹⁵

Question 30

Doppler effect

Answer 30

Change in wavelength caused by the relative motion between wave source and an observer
Δλ / λ = v/c

Question 31

Red shift

Answer 31

Apparent increase in wavelength of electromagnetic radiation caused when the source is moving away relative to the observer

Question 32

Hubble’s law

Answer 32

Recessional velocity of a galaxy is directly proportional to its distance from the earth

Question 33

Hubble’s constant

Answer 33

Constant of proportionality for Hubble’s Law

Question 34

What temperature does the wavelength of CMBR correspond to?

Answer 34

2.7 K, the same as the average temperature of the universe

Question 35

Cosmological principle

Answer 35

The universe is isotropic and homogeneous as long as a large enough volume is considered

Question 36

Dark matter

Answer 36

Cannot be seen, does not emit or absorb EM radiation

Undetectable directly but its effect on the gravity of galaxies can be indirectly used to detect its presence

Question 37

Dark energy

Answer 37

Type of energy that permeates the whole universe and opposes the gravitation between galaxies via the exertion of negative pressure
Detected by rate of expansion of universe