Astronomy A-Z

Astronomy A-Zimage preview

If you’re interested in sky watching, but have trouble remembering all of the jargon, here’s a quick and easy rundown of some common astronomy terms.

Aphelion: The point during orbit when a planet or other body is farthest from the Sun.

Binary: Two stars that revolve around a common center of gravity.

Circumpolar Star: A star that always stays above the horizon.

Dwarf Planet: A celestial body orbiting the Sun that is massive enough to be rounded by its own gravity, but has not cleared the neighborhood around its orbit, and is not a satellite. Pluto was demoted to a Dwarf Planet in 2006.

Extragalactic: Outside of or beyond our own galaxy.

Fireball: An extremely bright meteor, up to several times brighter than the full Moon, sometimes accompanied by a sonic boom.

Galaxy: A large grouping of stars, found in a variety of shapes and sizes. Our galaxy, the Milky Way, is spiral-shaped and contains billions of stars.

Hydrogen: An element consisting of one electron and one proton. Hydrogen is the lightest of the elements and is the building block of the universe. Stars form from massive clouds of hydrogen gas.

Inferior Planet: A planet that orbits between the Earth and the Sun. Mercury and Venus are the only two inferior planets.

Jupiter: The fifth, and largest planet, in our solar system, Jupiter is more than 1,000 times larger than the Earth and is made primarily of hydrogen and helium gas.

Kuiper Belt: A large ring of icy objects near the orbit of Neptune.

Light Year: The distance light travels in a year, approximately 5.8 trillion miles.

Magnitude: The measure of a star or other object’s brightness in the sky.

Nebula: An illuminated cloud of dust and gas made from the raw material of stars.

Occultation: When one celestial body conceals another from view. An Eclipse is an Occultation.

Perihelion: The point during orbit when a planet or other body is closest to the Sun.

Quasar: Any of several extremely bright objects located in remote areas of the universe.

Radiant: The point in the sky where meteors seem to originate.

Satellite: Any natural or artificial object that orbits around a planet.

Terrestrial Planet: A planet, like Earth, composed primarily of rock and iron.

Umbra: The area of total darkness during an eclipse.

Variable Star: A star that fluctuates in brightness.

White Dwarf: A very small, white star formed when a larger star exhausts its fuel supply and collapses.

X-ray Star: A star that radiates a large proportion of x-rays.

Yellow Dwarf: An ordinary, stable star. The Sun is a Yellow Dwarf.

Zenith: The point directly overhead when looking up.

This article was published by the staff at Farmers' Almanac. Interested in becoming a guest author? Contact us to let us know!

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