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The Milky Way is the galaxy that includes the Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the...

A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby obscuring the view of the Sun from a small part of Earth, totally or partially...

An apsis (from Ancient Greek ἁψίς (hapsís) 'arch, vault'; pl. apsides /ˈæpsɪˌdiːz/ AP-sih-deez) is the farthest or nearest point in the orbit of a planetary...

The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to...

A lunar eclipse is an astronomical event that occurs when the Moon moves into the Earth's shadow, causing the Moon to be darkened. Such an alignment occurs...

The European Space Agency (ESA) is a 22-member intergovernmental body devoted to space exploration. With its headquarters in Paris and a staff of around...

A neutron star is the collapsed core of a massive supergiant star. It results from the supernova explosion of a massive star—combined with gravitational...

A binary star or binary star system is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night...

Alpha Centauri (α Centauri, α Cen, or Alpha Cen) is a triple star system in the southern constellation of Centaurus. It consists of three stars: Rigil...

Apparent magnitude (m) is a measure of the brightness of a star or other astronomical object. An object's apparent magnitude depends on its intrinsic luminosity...

Cassini–Huygens (/kəˈsiːni ˈhɔɪɡənz/ kə-SEE-nee HOY-gənz), commonly called Cassini, was a space-research mission by NASA, the European Space Agency (ESA)...

An atmosphere (from Ancient Greek ἀτμός (atmós) 'vapour, steam' and σφαῖρα (sphaîra) 'sphere') is a layer of gasses that envelop an astronomical object...

A spacecraft is a vehicle that is designed to fly and operate in outer space. Spacecraft are used for a variety of purposes, including communications,...

The expansion of the universe is the increase in distance between gravitationally unbound parts of the observable universe with time. It is an intrinsic...

New Horizons is an interplanetary space probe launched as a part of NASA's New Frontiers program. Engineered by the Johns Hopkins University Applied Physics...

A natural satellite is, in the most common usage, an astronomical body that orbits a planet, dwarf planet, or small Solar System body (or sometimes another...

Space Shuttle Columbia (OV-102) was a Space Shuttle orbiter manufactured by Rockwell International and operated by NASA. Named after the first American...

Brown dwarfs are substellar objects that have more mass than the biggest gas giant planets, but less than the least massive main-sequence stars. Their...

Right ascension (abbreviated RA; symbol α) is the angular distance of a particular point measured eastward along the celestial equator from the Sun at...

In celestial mechanics, an orbit (also known as orbital revolution) is the curved trajectory of an object such as the trajectory of a planet around a star...