Astronomy (from Greek: ἀστρονομία, literally meaning the science that studies the laws of the stars) is a natural science that studies celestial objects and phenomena. It uses mathematics, physics, and chemistry to explain their origin and evolution. Objects of interest include planets, moons, stars, nebulae, galaxies, and comets. Relevant phenomena include supernova explosions, gamma ray bursts, quasars, blazars, pulsars, and cosmic microwave background radiation. More generally, astronomy studies everything that originates beyond Earth's atmosphere.
An astronaut (or cosmonaut) is a person trained by a human spaceflight program to command, pilot, or serve as a crew member of a spacecraft.
Although generally reserved for professional space travelers, the terms are sometimes applied to anyone who travels into space, including scientists, politicians, journalists, and tourists.
An astronaut (or cosmonaut) is a person trained by a human spaceflight program to command, pilot, or serve as a crew member of a spacecraft.
Although generally reserved for professional space travelers, the terms are sometimes applied to anyone who travels into space, including scientists, politicians, journalists, and tourists.
The Solar System is the gravitationally bound system of the Sun and the objects that orbit it, either directly or indirectly. Of the objects that orbit the Sun directly, the largest are the eight planets, with the remainder being smaller objects, the dwarf planets, and small Solar System bodies. Of the objects that orbit the Sun indirectly—the natural satellites—two are larger than the smallest planet, Mercury.
Spaceflight (or space flight) applies astronautics to fly spacecraft into or through outer space, either with or without humans on board. Most spaceflight is uncrewed and conducted mainly with spacecraft such as satellites in orbit around Earth and includes space probes for flights beyond Earth orbit. Such spaceflight operates either by telerobotic or autonomous control.
Spaceflight (or space flight) applies astronautics to fly spacecraft into or through outer space, either with or without humans on board. Most spaceflight is uncrewed and conducted mainly with spacecraft such as satellites in orbit around Earth and includes space probes for flights beyond Earth orbit. Such spaceflight operates either by telerobotic or autonomous control.
A planet is an astronomical body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and – according to the International Astronomical Union but not all planetary scientists – has cleared its neighboring region of planetesimals.