Universe Glossary Flashcards
Define nebulae
Large clouds of gas and dust in space, which either form the raw material for new stars, or are produced when a star explodes.
Define star
A celestial body of hot gases (mainly hydrogen) that radiates energy derived from thermonuclear reactions in its interior.
Define solar system
The collection of planets, moons, asteroids, comets, gas, dust and other objects orbiting a star.
Define galaxy
Large (billion+) groups of stars gravitationally bound to and orbiting each other.
Define black hole
An object so massive that nothing, not even light, can escape its gravitational attraction. Usually left behind after very large stars go supernova.
Define big bang theory
The theory says that the universe started expanding roughly 14 billion years ago from an extremely dense and incredibly hot initial state.
Define satellite
A satellite is a moon, planet or machine that orbits a planet or star.
Define telescope
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.
Define universe
The totality of space and time, along with all the matter and energy in it.
Define doppler effect
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.
Define supernova
An exploding star, caused when a very large star runs out of ‘fuel’ and collapses.
Define electromagnetic spectrum
The range of wavelengths or frequencies over which electromagnetic radiation extends.
Define light year
Distance travelled by light in one year, used to measure distance in space.
Define space probes
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.
Define gravity
The universal force of attraction acting between all matter (proportional to mass of the objects, inversely proportional to distance between the objects).
Define scientific law
Statements based on repeated experiments or observations, that describe or predict a range of natural phenomena.
Define scientific theory
A carefully thought-out explanation for observations of the natural world that has been constructed using the scientific method
Define protostar
Aprotostaris a very youngstarthat is still gathering mass from its parentmolecular cloud.
Define red giant
A star that has exhausted the supply of hydrogen in its core and has begunthermonuclear fusionof hydrogen in a shell surrounding the core.
Define planetary nebula
An expanding, glowing shell of hot gas (plasma) that is cast off towards the end of a low-massstar’s life.
Define white dwarf
Astellar core remnantcomposed mostly ofelectron-degenerate matter.
Define neutron star
Thecollapsedcoreof a massivesupergiant star.
Define accretion disc
A rotating disc of matter formed by accretion around a massive body (such as a black hole) under the influence of gravitation.
Define event horizon
A boundary inspacetimethrough which matter and light can pass only inward towards the mass of the black hole.
Define singularity
A condition in which gravity is so intense that spacetime itself breaks down catastrophically.
Define moons
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.
Define comets
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.
Define asteroids
A small rocky body orbiting the sun
Define meteor
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.
Define meteorite
A piece of rock or metal that has fallen to the earth’s surface from outer space as a meteor.
Define reflection
The change in direction of a wave as it bounce off the surface of a substance.
Define refraction
The change in direction of a wave due to a change in its speed when it passes from one medium to another
Define spaghettification
The process by which (in some theories) an object would be stretched and ripped apart by gravitational forces on falling into a black hole.
Define stellar winds
A continuous flow of charged particles from a star.
