19.Stars

Question 1

Absorption Line Spectrum

Answer 1

A spectrum consisting of dark lines at specific frequencies that have been absorbed by the gases present. Elements can only absorb certain energies, and therefore frequencies, of photons.

Question 2

Astronomical Unit

Answer 2

The mean distance of the earth to the sun.

Question 3

Big Bang Theory

Answer 3

The theory that the universe originated as a small, dense and hot region that expanded and cooled forming the structures in the universe we see today.

Question 4

Chandrasekhar Limit

Answer 4

The maximum mass that a white dwarf star can have
whilst remaining stable.

Question 5

Comets

Answer 5

Concentrated clusters of ice and dust that travel through space. When near the sun, they begin to melt and so leave a trail as they move.

Question 6

Continuous Spectrum

Answer 6

A spectrum that covers a full range of frequencies without
any gaps. The electromagnetic spectrum is an example of a continuous spectrum.

Question 7

Cosmological Principle

Answer 7

A principle stating that the universe is isotropic (same in
all directions to all observers) and homogenous (matter is distributed evenly).

Question 8

Dark Energy

Answer 8

An energy that is responsible for the acceleration in the expansion of the universe which cannot be explained by any observable energy.

Question 9

Doppler Effect

Answer 9

The apparent change in the wavelength of a wave as the source moves relative to an observer. For a source moving away the wavelength increases, for a source moving towards the observer the wavelength decreases.

Question 10

Electron Degeneracy Pressure

Answer 10

The outwards force, resisting the inwards force of gravity, produced as a result of multiple electrons not being able to exist in identical states in an energy level.

Question 11

Emission Line Spectrum

Answer 11

A series of bright lines at specific frequencies that
have been emitted by the gases present. Elements can only release photons of certain energies, and therefore frequencies.

Question 12

Galaxies

Answer 12

Collections of billions of stars, planets, gases and dust, held together by gravitational attraction.

Question 13

Hertzsprung-Russell Diagram

Answer 13

A visual representation of the lifecycle of a star. It is a plot of luminosity against temperature.

Question 14

Hubble’s Law

Answer 14

The speed of a galaxy moving away from ours is proportional to its distance away from us. The constant of proportionality is Hubble’s constant

Question 15

Light-Year

Answer 15

The distance travelled through space by a photon in a year.

Question 16

Nebula

Answer 16

A cloud of dust and gas in space.

Question 17

Neutron Star

Answer 17

An incredibly dense star that is formed when the core of a large
star collapses. Protons and electrons are forced together under gravity to form
neutrons.

Question 18

Parsec

Answer 18

The distance at which the angle of parallax is 1 arcsecond.

Question 19

Planet

Answer 19

A body that orbits around a star, in our case, the Sun.

Question 20

Planetary Satellites

Answer 20

Bodies that orbit a planet. The gravitational force of the
planet’s mass provides the centripetal force of rotation.

Question 21

Red-Giant

Answer 21

A stage in the life cycle of a star less than 3 solar masses, in which the hydrogen has run out and the temperature of the star increases. Helium nuclei fuse to form heavier elements.

Question 22

Solar Systems

Answer 22

A collection of planets that orbit a common star.

Question 23

Stefan’s Law

Answer 23

A law stating that the power output (luminosity) of a star is directly proportional to its surface area and its absolute temperature to the 4th power.

Question 24

Stellar Parallax

Answer 24

The change in position of an object depending on the viewing
angle. It can be used to estimate the distance of a star, based on how much it moves relative to the background of stars in the time it takes for the earth to move half an orbit.

Question 25

Supernova

Answer 25

When a star greater than 1.4 solar masses dies, the core collapses rapidly inward and becomes rigid. The outer layers then fall inward and rebound
off of the core in a shockwave, causing heavy elements to be fused and distributed into space in an explosion.

Question 26

Universe

Answer 26

The name given to all space and matter.

Question 27

White Dwarf

Answer 27

A dense star, similar mass to the sun, similar size to the earth. A
final stage of a low mass star’s life with low luminosity.

Question 28

Wien’s Displacement Law

Answer 28

A law stating that the peak wavelength of emitted
radiation is inversely proportional to its absolute temperature.