Acronym in astronomy: KBO for Kuiper belt object

In astronomy, KBO stands for Kuiper belt object. A KBO is an icy object beyond the orbit of Neptune. The KBOs form a disc-shaped ring—named Kuiper belt—billions of kilometers away from the sun [1]. The Kuiper belt is named after the Dutch-born astronomer Gerard Peter Kuiper (1905-1973), who proposed the existence of such a belt in 1951 [2]. The discovery in 1992 of object 1992 QB₁, moving beyond the orbit of Neptune [3], marks the beginning of ongoing discoveries and studies of KBOs.

Along with objects of the Oort Cloud, KBOs are trans-Neptunian objects  (TNOs). Some of them resemble Pluto and became to be called Plutinos, rivaling Pluto in mass, size and other properties [4]: In 2003, Brown, Trujillo and Rabinowitz photographed a KBO that they later revealed as the ninth largest solar system body with a mass 27 percent larger than that of Pluto. This objects, officialy designated 2003 UB313, was first named Xena after a fictional warrior princess [5], but was named Eris (Greek goddess of strife, discord, contention and rivalry [6]) in 2006 by the International Astronomical Union (IAU), following the convention of  naming TNOs after creation deities.

Occasionally, the term Edgeworth-Kuiper belt is used instead of simply Kuiper belt to also honor Kenneth Essex Edgeworth (1880-1972), who wrote an early  paper on the evolution of the planetary system and reasoned (speculated) that a reservoir of objects must exist beyond the planets, which, on their trajectory,  enter the inner solar system and appear as comets [7]. Synonymously for KBO, EKBO is used as an acronym for Edgeworth-Kuiper belt object.

If on schedule, NASA's New Horizon spacecraft, which started its journey in January 2006, will visit the Edgeworth-Kuiper belt in 2015, after flying by dwarf planet Pluto [1].

Keywords: astronomy, planetary science, solar system, celestial bodies, terminology.

References and more to explore
[1]  NASA > Solar System Exploration > Kuiper Belt & Oort Cloud: Overview: solarsystem.nasa.gov/planets/profile.cfm?Object=KBOs.
[2] The New Netherland Institute > Kuiper, Gerard Peter (1905-1973): www.nnp.org/nni/Publications/Dutch-American/kuiper.html. 
[3] David Jewitt and Jane Luu: Discovery of the candidate Kuiper belt object 1992 QB₁. Nature April 22, 1993, 362, pp. 730-732. doi: 10.1038/362730a0.
[4] Neil deGrasse Tyson: The Pluto Files. W. W. Norton & Company, New York and London, 2009; page 89 to 93.
[5] Andy Lloyd: Xena (Eris) and other Extraordinary EKBOs [www.darkstar1.co.uk/xena.html].
[6] Theoi Greek Mythology > Eris: www.theoi.com/Daimon/Eris.html.
[7] Andrew Hollis: Kenneth Essex Edgeworth - A biographical note. J. Brit. Astron. Assoc. 1996, 106 (6), p. 354 [www.britastro.org/jbaa/archive/edgewort.htm].