Astrobiology Glossary B – Space

Term Definition
Bacteria One of three domains of life, along with the Archaea and the Eucarya. The bacterial domain includes all prokaryotic organisms not classified as archaea.
Barred Spiral Galaxy A galaxy with a ‘bar’ of stars and interstellar matter, such as dust and gas, slicing across its center. The Milky Way is thought to be a barred spiral galaxy.
Baseline The distance between two or more telescopes that are working together as a single instrument to observe celestial objects. The wider the baseline, the greater the resolving power.
BATSE (Burst and Transient Source Experiment) A high-energy astrophysics ‘experiment’ used to investigate gamma-ray bursts (GRBs). BATSE consisted of eight detectors that were mounted on the corners of NASA’s Earth-orbiting Compton Gamma-Ray Observatory, whose mission ended in 2000.
BeppoSAX A space-based X-ray observatory built and operated by the Italian Space Agency and the Netherlands Agency for Aerospace Programs. BeppoSAX has been instrumental in identifying and locating gamma-ray bursts.
Big Bang The cosmic explosion that marked the origin of the universe
Big Bang A broadly accepted theory for the origin and evolution of our universe. The theory says that the observable universe started roughly 15 billion years ago from an extremely dense and incredibly hot initial state.
Binary Star System A system of two stars orbiting around a common center of mass that are bound together by their mutual gravitational attraction.
Biome A major regional or global biotic community, such as a grassland or desert, characterized chiefly by the dominant forms of plant life and the prevailing climate.
Black Hole A region of space containing a huge amount of mass compacted into an extremely small volume. A black hole’s gravitational influence is so strong that nothing, not even light, can escape its grasp. Swirling disks of material – called accretion disks – may surround black holes, and jets of matter may arise from their vicinity.
Blue Star A massive, hot star that appears blue in color. Spica in the constellation Virgo is an example of a blue star.
Blueshift The shortening of a light wave from an object moving toward an observer. For example, when a star is traveling toward Earth, its light appears bluer.
Bolide Large, brilliant meteors that enter the Earth’s atmosphere. Friction between a fast-moving meteor and Earth’s air molecules generates tremendous heat, which causes the meteor to heat up, glow, and perhaps disintegrate. In some cases, the meteor literally explodes, leaving a visible cloud that dissipates slowly.
Brash Ice Accumulations of floating ice made up of fragments not more than 2 meters across; the wreckage of other forms of ice
Brown Dwarf An object too small to be an ordinary star because it cannot produce enough energy by fusion in its core to compensate for the radiative energy it loses from its surface. A brown dwarf has a mass less than 0.08 times that of the Sun.
Bulge The spherical structure at the center of a spiral galaxy that is made up primarily of old stars, gas, and dust. The Milky Way’s bulge is roughly 15,000 light-years across.

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