Astronomy Resource Guide: Concepts and Terms

Totality of matter and energy in existence. The study of the origin of the universe, or cosmos, is known as cosmogony, and that of its...

Grouping of millions or billions of stars, held together by gravity. There are billions of galaxies in the universe. There are...

The sun and the surrounding planets, natural satellites , dwarf planets, asteroids, meteoroids, and comets that are bound by its gravity. The...

In astronomy, the explosive event that marked the origin of the universe as we know it. At the time of the Big Bang, the entire...

Star at the centre of our Solar System. It is about 5 billion years old, with a predicted lifetime of 10 billion years; its...

Natural satellite of a planet (see satellite, natural) or dwarf planet, in particular, the single natural satellite of the earth. The...

Luminous globe of gas, mainly hydrogen and helium, which produces its own heat and light by nuclear reactions. Although stars shine...

Any of a class of rotating oblate spheroid bodies of substantial size that orbit the Sun or other stars and shine only by the light reflected from their primaries.

Planetoid, or minor planet, small body orbiting the sun. More than 10,000 asteroids have orbits sufficiently well known to have been cataloged...

[Gr.,=longhaired], a small celestial body consisting mostly of dust and gases that moves in an elongated elliptical or nearly parabolic orbit...

Appearance of a small particle flying through space that interacts with the earth's upper atmosphere. While still outside the atmosphere, the...

Increase in the number of meteors observed in a particular part of the sky. The trails of the meteors of a meteor shower all appear to be...

In astronomy, celestial object of such extremely intense gravity that it attracts everything near it and in some instances prevents everything...

Material that is believed to make up (along with dark energy) more than 90% of the mass of the universe but is not readily visible because it...

Faint star that suddenly erupts in brightness by 10,000 times or more, remains bright for a few days, and then fades...

A massive star in the latter stages of stellar evolution that suddenly contracts and then explodes, increasing its energy output as much as a...

In astronomy, a type of star that is abnormally faint for its white-hot temperature (see mass-luminosity relation). Typically, a white dwarf...

In astronomy, celestial body that is larger than a planet but does not have sufficient mass to convert hydrogen into helium via nuclear fusion...

Pair of stars moving in orbit around their common centre of mass. Observations show that most stars are binary, or even multiple...

One of the 88 areas into which the sky is divided for the purposes of identifying and naming celestial objects. The first...

[Gr.,=failing], in astronomy, partial or total obscuring of one celestial body by the shadow of another. Best known are the lunar eclipses...

Any alteration in the relative apparent positions of objects produced by a shift in the position of the observer. In astronomy the term is used...

In astronomy, path in space described by a body revolving about a second body where the motion of the orbiting bodies is dominated by their...

Force of attraction that arises between objects by virtue of their masses. The larger the mass of an object the more strongly it...

Area of science that aims at a comprehensive theory of the structure and evolution of the entire physical universe. Modern Cosmological...

Or astrobiology, search for extraterrestrial life within the solar system and throughout the universe. Philosophical speculation that there...

Body of scientific knowledge as it relates to space exploration; it is sometimes also called astronautics. Space science draws on the...

The investigation of physical conditions in space and on stars, planets, and other celestial bodies through the use of artificial satellites...

Study of the relative position of the planets and stars in the belief that they influence...

Branch of science traditionally defined as the study of matter, energy, and the relation between them; it was called natural philosophy...