Universe Glossary

Question 1

Define nebulae

Answer 1

Large clouds of gas and dust in space, which either form the raw material for new stars, or are produced when a star explodes.

Question 2

Define star

Answer 2

A celestial body of hot gases (mainly hydrogen) that radiates energy derived from thermonuclear reactions in its interior.

Question 3

Define solar system

Answer 3

The collection of planets, moons, asteroids, comets, gas, dust and other objects orbiting a star.

Question 4

Define galaxy

Answer 4

Large (billion+) groups of stars gravitationally bound to and orbiting each other.

Question 5

Define black hole

Answer 5

An object so massive that nothing, not even light, can escape its gravitational attraction. Usually left behind after very large stars go supernova.

Question 6

Define big bang theory

Answer 6

The theory says that the universe started expanding roughly 14 billion years ago from an extremely dense and incredibly hot initial state.

Question 7

Define satellite

Answer 7

A satellite is a moon, planet or machine that orbits a planet or star.

Question 8

Define telescope

Answer 8

A device for looking at objects a long distance away. They can be in space or on the ground, use reflection or refraction, and there is a different type of telescope for every part of the electromagnetic spectrum.

Question 9

Define universe

Answer 9

The totality of space and time, along with all the matter and energy in it.

Question 10

Define doppler effect

Answer 10

An increase (or decrease) in the frequency of sound, light, or other waves as the source and observer move towards (or away from) each other.

Question 11

Define supernova

Answer 11

An exploding star, caused when a very large star runs out of ‘fuel’ and collapses.

Question 12

Define electromagnetic spectrum

Answer 12

The range of wavelengths or frequencies over which electromagnetic radiation extends.

Question 13

Define light year

Answer 13

Distance travelled by light in one year, used to measure distance in space.

Question 14

Define space probes

Answer 14

A probe is a spacecraft that travels through space to collect scientific data. Probes do not have astronauts. Probes send data back to Earth for scientists to study.

Question 15

Define gravity

Answer 15

The universal force of attraction acting between all matter (proportional to mass of the objects, inversely proportional to distance between the objects).

Question 16

Define scientific law

Answer 16

Statements based on repeated experiments or observations, that describe or predict a range of natural phenomena.

Question 17

Define scientific theory

Answer 17

A carefully thought-out explanation for observations of the natural world that has been constructed using the scientific method

Question 18

Define protostar

Answer 18

Aprotostaris a very youngstarthat is still gathering mass from its parentmolecular cloud.

Question 19

Define red giant

Answer 19

A star that has exhausted the supply of hydrogen in its core and has begunthermonuclear fusionof hydrogen in a shell surrounding the core.

Question 20

Define planetary nebula

Answer 20

An expanding, glowing shell of hot gas (plasma) that is cast off towards the end of a low-massstar’s life.

Question 21

Define white dwarf

Answer 21

Astellar core remnantcomposed mostly ofelectron-degenerate matter.

Question 22

Define neutron star

Answer 22

Thecollapsedcoreof a massivesupergiant star.

Question 23

Define accretion disc

Answer 23

A rotating disc of matter formed by accretion around a massive body (such as a black hole) under the influence of gravitation.

Question 24

Define event horizon

Answer 24

A boundary inspacetimethrough which matter and light can pass only inward towards the mass of the black hole.

Question 25

Define singularity

Answer 25

A condition in which gravity is so intense that spacetime itself breaks down catastrophically.

Question 26

Define moons

Answer 26

A moon is any natural body orbiting a planet. Earth has one, and some planets have over 20. Only Mercury and Venus don’t have any at all.

Question 27

Define comets

Answer 27

These are balls of snow, ice and rock. They spend a lot of time a long way from the sun because they do not orbit the sun in a circle.

Question 28

Define asteroids

Answer 28

A small rocky body orbiting the sun

Question 29

Define meteor

Answer 29

A small body of matter from outer space that enters the earth’s atmosphere, becoming incandescent as a result of friction and appearing as a streak of light.

Question 30

Define meteorite

Answer 30

A piece of rock or metal that has fallen to the earth’s surface from outer space as a meteor.

Question 31

Define reflection

Answer 31

The change in direction of a wave as it bounce off the surface of a substance.

Question 32

Define refraction

Answer 32

The change in direction of a wave due to a change in its speed when it passes from one medium to another

Question 33

Define spaghettification

Answer 33

The process by which (in some theories) an object would be stretched and ripped apart by gravitational forces on falling into a black hole.

Question 34

Define stellar winds

Answer 34

A continuous flow of charged particles from a star.