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planetary system

(Encyclopedia)planetary system, a star and all the celestial bodies bound to it by gravity, especially planets and their natural satellites. Until the last decade of the 20th cent., the only planetary system known ...

Hubble's law

(Encyclopedia)Hubble's law, in astronomy, statement that the distances between galaxies (see galaxy) or clusters of galaxies are continuously increasing and that therefore the universe is expanding. Hubble's law ...

space probe

(Encyclopedia)space probe, space vehicle carrying sophisticated instrumentation but no crew, designed to explore various aspects of the solar system (see space exploration). Unlike an artificial satellite, which is...

neutrino

(Encyclopedia)neutrino no͞otrēˈnō [key] [Ital.,=little neutral (particle)], elementary particle with no electric charge and a very small mass emitted during the decay of certain other particles. The neutrino wa...

Newton, Sir Isaac

(Encyclopedia)Newton, Sir Isaac, 1642–1727, English mathematician and natural philosopher (physicist), who is considered by many the greatest scientist that ever lived. Newton was his university's representa...

nucleosynthesis

(Encyclopedia)nucleosynthesis or nucleogenesis, in astronomy, production of all the chemical elements from the simplest element, hydrogen, by thermonuclear reactions within stars, supernovas, and in the big bang at...

Aztec

(Encyclopedia)Aztec ăzˈtĕkˌ [key], Indian people dominating central Mexico at the time of the Spanish conquest. Their language belonged to the Nahuatlan subfamily of Uto-Aztecan languages. They arrived in the V...

supernova

(Encyclopedia)supernova, a massive star in the latter stages of stellar evolution that suddenly contracts and then explodes, increasing its energy output as much as a billionfold. Supernovas are the principal distr...

orbit

(Encyclopedia)CE5 Important points in a planet's orbit as seen from the earth orbit, in astronomy, path in space described by a body revolving about a second body where the motion of the orbiting bodies is domi...

Aristotle

(Encyclopedia)Aristotle ărˌĭstŏtˈəl [key], 384–322 b.c., Greek philosopher, b. Stagira. He is sometimes called the Stagirite. After the decline of Rome, Aristotle's work was lost in the West. However, in ...