Dictionary

planet: A celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, not massive enough to cause thermonuclear fusion, and has cleared its neighboring region.

planetesimals: Solid objects thought to exist in protoplanetary disks and in debris disks.

Salyut Series: A series of space stations sent by the Soviet Union to orbit between 1971 and 1991. They were designed for long periods of human habitation.

Skylab: The first U.S. space station.

solar system: Consists of the various non-stellar objects orbiting a star such as planets, moons, asteroids, meteoroids, comets and cosmic dust; the sun together with its planetary system.

solar wind: A stream of charged particles which are ejected from the upper atmosphere of the sun that consists mostly of high-energy electrons and protons.

space shuttle external tank: Also referred to as ET; the component of the space shuttle launch vehicle that contains the liquid hydrogen fuel and liquid oxygen oxidizer. During lift-off and landing, this fuels and oxidizes under pressure to the three space shuttle main engines.

space shuttle orbiter: The orbital vehicle of a space shuttle. It has a reusable winged space plane, which is a mixture of rocket, spacecraft and aircraft.

space shuttle solid rocket booster: Also referred to as the SRB; the rocket that provides 83 percent of liftoff thrust for a space shuttle.

space shuttle: The spacecraft currently used by the U.S. government for its human spaceflight missions.

SPACEHAB Inc.: An aerospace company headquartered in Webster, Texas, that provides commercial space products and services to NASA.

spaceplane: A rocket plane designed to pass the edge of space that combines some of the features of an aircraft and some of a spacecraft.

stellar remnant: An object that is small for its mass, such as a white dwarf, neutron star or black hole.