An Etymological Dictionary of Astronomy and Astrophysics
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The region of the → solar system located between → Mars and → Jupiter where over a million objects bigger than 1 km across orbit the Sun. Another region populated by minor bodies lies beyond the orbit of → Neptune, the → Kuiper belt.

→ asteroid; → belt.

A strip of leather or cloth worn around the waist. Something that resembles this type of band, e.g. → Gould's Belt, → Belt of Venus.

O.E. belt, from P.Gmc. *baltjaz, from L. balteus "girdle;" → Orion.

Kamarband "belt," from kamar "waist" (Mid.Pers. kamar "waist; belt, girdle," Av. kamarâ- "belt") + band "a band, tie, belt."

→ Orion's Belt.

→ belt; → Orion.

A pink to brownish border above the horizon separating the Earth's dark shadow on the sky from the sky above it. The Belt of Venus appears during a cloudless twilight just before sunrise or after sunset. It is due to scattered red sunlight in the atmosphere. Also called anti-twilight arc.

→ belt, → Venus.

A band of hot, young stars (O and B types) and molecular clouds that stretches around the sky. It is tilted by about 20 degrees with respect to the Galactic plane, and has a diameter of about 3000 light-years.

Named after the American astronomer Benjamin A. Gould (1824-1896), who discovered it in 1879 by studying the distribution of the nearest luminous stars in space; → belt.

A region of the → Solar System extending roughly from the orbit of → Neptune, or 30 → astronomical units (AU), to 50 AU from the Sun that contains many small icy bodies. The Kuiper belt is now considered to be the source of the → short-period comets.

Named after Gerard Peter Kuiper (1905-1973), a Dutch-born American astronomer, who predicted the belt in 1951. He is also considered the father of modern planetary science for his contributions to the study of our solar system; → belt.

A → Solar System object belonging to the → Kuiper belt. The largest known objects of this type are → Pluto and its moon → Charon, → Quaoar, → Sedna, and → Orcus. See also → trans-Neptunian object.

→ Kuiper belt; → object.

The area between → Mars and → Jupiter where most of the → asteroids in our → solar system are found.

→ main; → belt.

Three prominent stars in the central regions of the constellation → Orion that align to form the "belt" of the mythological Hunter. They are → Alnitak (ζ Ori), → Alnilam (ε Ori), and → Mintaka (δ Ori). The easternmost star Alnitak is separated from the middle one, Alnilam, by 1°.36, and the westernmost Mintaka has an angular distance of 1°.23 from Alnilam. Their distance is between 800 and 1,300 → light-years from Earth. They probably formed inside the same → molecular cloud less than 10 million years ago.

→ Orion; → belt.

A ring-shaped region in the → magnetosphere of a planet in which charged particles are trapped by the planet's magnetic field. The radiation belts surrounding Earth are known as the → Van Allen belts.

→ radiation; → belt.

The ring-shaped regions of charged particles surrounding the Earth from 1 to 6 Earth radii into space. The charged particles are trapped in by the Earth's magnetic field. The inner belt is between 1.2 and 4.5 Earth radii and contains high-energy electrons and protons which originate mainly from interactions between cosmic rays and the upper atmosphere. The outer belt, located between 4.5 and 6.0 Earth radii, contains lower-energy charged particles mainly coming from the solar wind.

Named after James Van Allen (1914-2006), who discovered the belts in 1958 based on measurements made by Explorer 1, the USA's first successful artificial satellite; → belt.

→ zodiac.

→ zodiacal; → belt.