On September 23, 1846, French scientists discovered Neptune, the outermost planet in our solar system. Neptune is one of only two planets in the solar system (along with Uranus) only visible through a telescope.
Neptune is the only planet discovered by mathematical prediction. Long before its discovery, astronomers hypothesized the existence of Neptune because Uranus seemed to be affected by an unknown source of gravity. Several mathematicians successfully calculated the approximate position of the planet, which helped astronomers know where to look.
Since its discovery, scientists have learned much about Neptune. In 1989, NASA’s Voyager 2 spacecraft provided images of the planet, which appears bright blue due to the methane in its upper atmosphere. Neptunian rings and moons were also identified.
Term Part of Speech Definition Encyclopedic Entry approximate Adjective
generally or near an exact figure.
person who studies space and the universe beyond Earth's atmosphere.
layers of gases surrounding a planet or other celestial body.
Encyclopedic Entry: atmosphere calculate Verb
to reach a conclusion by mathematical or logical methods.
physical force by which objects attract, or pull toward, each other.
to form a statement or suggestion that explains certain questions about certain facts.
person who studies the theory and application of quantities, groupings, shapes, and their relationships.
chemical compound that is the basic ingredient of natural gas.
natural satellite of a planet.
Encyclopedic Entry: moon planet Noun
large, spherical celestial body that regularly rotates around a star.
Encyclopedic Entry: planet solar system Noun
the sun and the planets, asteroids, comets, and other bodies that orbit around it.
scientific instrument that uses mirrors to view distant objects.