Space Vocabulary

moon — a natural satellite that orbits another object in space: “Earth has one moon.”

galaxy — an enormous system of stars, planets, and other matter held together by gravity: “Our galaxy is called the Milky Way.”

universe — everything that exists, including all galaxies, stars, and planets: “Scientists study how the universe began.”

star / planet — a star is an enormous object that produces energy, including light and heat; a planet is a large celestial body that usually orbits a star and does not produce its own visible light in the same way a star does: “The night sky was full of stars, with one bright planet visible near the horizon.”

spacecraft — a vehicle designed to travel in space: “The spacecraft carried a crew of four.”

astronaut — a person trained to travel and work in space: “She trained for years to become an astronaut.”

launch — to send a spacecraft into space: “The rocket launched early in the morning.”

orbit / rotate — to orbit means to travel in a path around another object, such as a planet around a star; to rotate means to spin around one’s own axis: “The Earth rotates once a day and orbits the sun once a year.”

explore — to travel through or study something unfamiliar in order to learn more about it: “The mission was designed to explore a distant moon.”

discover — to find or learn about something for the first time: “Astronomers discovered a new object at the edge of the solar system.”

telescope — an instrument used to observe distant objects, especially in space: “She used a telescope to look at the rings of a planet.”

satellite / probe — an artificial satellite is a human-made object placed in orbit around another body, often for observation, communication, navigation, or research; a space probe is an uncrewed spacecraft sent to collect information about space or celestial bodies, and it may fly past, orbit, or land on its target, so a probe can itself act as an orbiter. The word satellite can also describe a natural object, such as a moon, when context makes that clear: “An artificial satellite relayed the signal back to Earth, while a probe entered orbit around a distant moon to begin its survey.”

astronomy — the scientific study of stars, planets, and other objects in space: “She’s always been interested in astronomy.”

observatory — a building or facility equipped for observing the sky: “The observatory is open to visitors at night.”

eclipse — an event in which one object in space blocks the light of another: “They watched the eclipse together.”

comet / asteroid — a comet is made largely of ice, dust, and rock, and may develop a glowing coma or tail when heated as it approaches the Sun; an asteroid is an object composed mainly of rock or metal, and the two can be similar in size: “The comet developed a glowing tail as it neared the Sun, while the nearby asteroid showed no such change.”

mission — a planned project with a specific goal, such as exploring a particular location: “The mission lasted nearly a year.”

crew — the group of people working together on a spacecraft or mission: “The crew worked together to complete each task.”

mission control — the team on the ground that communicates with and supports a spacecraft or crew: “Mission control monitored the launch closely.”

spacewalk — when an astronaut leaves a spacecraft to work outside it, usually while still connected to it: “She completed her first spacewalk during the mission.”