Astro Glossary

  • Balloon Astronomy

  • Barnard's Star

    A small, cool, and faint red-dwarf star six light-years from Earth. It is named for its discoverer, Edward Emerson Barnard.

  • Beehive Cluster, M44

    A bright cluster of several hundred stars that formed about 700 million years ago.

  • Beta Pictoris

    A young star system surrounded by a giant cloud of gas and dust that may by giving birth to planets.

  • Betelgeuse

    An orange supergiant star 650 light-years away in the constellation Orion. It forms Orion’s shoulder, and is the constellation’s second-brightest star, after Rigel. It is expected to end its life with a titanic explosion known as a supernova.

  • Big Bang

    A theoretical model of the “birth” of the observable universe, which suggests that the universe began as a rapid expansion of space and time from a single point, or singularity.

  • Big Dipper

    The Big Dipper is an “asterism” — a group of stars that forms an easy-to-see pattern, but that’s not a constellation in its own right. It forms the body and tail of the constellation Ursa Major, the big bear. The Big Dipper is found in the northern sky, and the outer stars in its bowl can be used to “point” to Polaris, the North Star.

  • Binary and Multi-Star Systems

    A binary is a pair of stars that orbit each other. A multi-star system consists of three or more stars. The stars in a binary or a multi-star system all formed from a single cloud of gas and dust, so they are true “siblings.”

  • Biology

  • Black Hole

    An object with such powerful gravity that nothing can escape from it, including light. The black hole’s mass is concentrated in a point of almost infinite density called a singularity. At the singularity itself, gravity is almost infinitely strong, so it crushes normal space-time out of existence. As the distance from the singularity increases, its gravitational influence lessens. At a certain distance, which depends on the singularity’s mass, the speed needed to escape from the black hole equals the speed of light. This distance marks the black hole’s “horizon,” which is like its surface. Anything that passes through the horizon is trapped inside the black hole. Black holes come in several varieties, depending on mass.

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