astronomy The area of science that deals with celestial objects, space and the physical universe. People who work in this field are called astronomers.
colleague Someone who works with another; a co-worker or team member.
descendant A blood relative of a person who lived during a previous time.
Jupiter (in astronomy) The solar system’s largest planet, it has the shortest day length (10 hours). A gas giant, its low density indicates that this planet is composed of light elements, such as hydrogen and helium. This planet also releases more heat than it receives from the sun as gravity compresses its mass (and slowly shrinks the planet).
moon The natural satellite of any planet.
Neptune The furthest planet from the sun in our solar system. It is the fourth largest planet in the solar system.
new moon The phase of the moon that appears fully dark, when viewed from Earth. At this time, the moon will sit between the earth and sun. So the lunar face lit by the sun is turned away from us.
planet A celestial object that orbits a star, is big enough for gravity to have squashed it into a roundish ball and has cleared other objects out of the way in its orbital neighborhood. To accomplish the third feat, the object must be big enough to have pulled neighboring objects into the planet itself or to have slung them around the planet and off into outer space. Astronomers of the International Astronomical Union (IAU) created this three-part scientific definition of a planet in August 2006 to determine Pluto’s status. Based on that definition, IAU ruled that Pluto did not qualify. The solar system now includes eight planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
satellite A moon orbiting a planet or a vehicle or other manufactured object that orbits some celestial body in space.
solar system The eight major planets and their moons in orbit around our sun, together with smaller bodies in the form of dwarf planets, asteroids, meteoroids and comets.
tweet Message consisting of 140 or fewer characters that is available to people with an online Twitter account.
Twitter An online social network that allows users to post messages containing no more than 280 characters (until November 2017, the limit had been just 140 characters).