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Roche limit

(Encyclopedia)Roche limit, the closest distance that a celestial body held together only by its own gravity can come to a planet without being pulled apart by the planet's tidal (gravitational) force. This distance...

Scholz's star

(Encyclopedia)Scholz's star, dim binary star system, consisting of a red dwarf and brown dwarf, in the constellation Monoceros, apparent magnitude 18.3. The red dwarf is a tiny star, with less than ten percent the ...

Arrokoth

(Encyclopedia)Arrokoth, trans-Neptunian object in the Kuiper Belt (see comet). First observed by the Hubble Space Telescope in 2014 and later nicknamed Ultima Thule (until its official naming in late 2019), it beca...

Bond, George Phillips

(Encyclopedia)Bond, George Phillips, 1825–65, American astronomer, b. near Boston, grad. Harvard, 1845. He became the assistant of his father, William Cranch Bond, and in 1859 succeeded him as director of the Har...

Star of Bethlehem, in the Gospels

(Encyclopedia)Star of Bethlehem, name given to the luminous celestial object rising in the sky that, as related in the Gospel of Matthew, led the Wise Men of the East to the manger in Bethlehem where Jesus was born...

Eris, in astronomy

(Encyclopedia)Eris, in astronomy, the largest known dwarf planet. Eris, whose highly eccentric elliptical orbit ranges from 38 AU to 97 AU and is inclined more than 44°, is the largest known object of the Kuiper b...

Sedna

(Encyclopedia)Sedna, in astronomy, the most distant known large object in the solar system. With a highly eccentric elliptical orbit that ranges from an estimated 76 AU to 937 AU, Sedna also has an extremely long o...

Olbers, Heinrich Wilhelm Matthäus

(Encyclopedia)Olbers, Heinrich Wilhelm Matthäus hīnˈrĭkh vĭlˈhĕlm mätĕˈo͝os ôlˈbərs [key], 1758–1840, German astronomer and physician. He originated (1797) the first satisfactory method for calculat...

Tombaugh, Clyde William

(Encyclopedia)Tombaugh, Clyde William tŏmˈbô [key], 1906–97, American astronomer, b. Streator, Ill. Although lacking formal training or a college degree, he was hired in 1929 as an assistant by the Lowell Obse...

space probe

(Encyclopedia)space probe, space vehicle carrying sophisticated instrumentation but no crew, designed to explore various aspects of the solar system (see space exploration). Unlike an artificial satellite, which is...

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