Sedna

Article By:

Stansberry, John Steward Observatory, The University of Arizona, Tucson, Arizona.

Last reviewed:February 2019

DOI:https://doi.org/10.1036/1097-8542.612400

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• Sedna, published January 2006:Download PDF Get Adobe Acrobat Reader

A distant object located in the inner Oort Cloud and likely a dwarf planet. Little is known about Sedna except where it is in the sky, how bright it appears, its color, its orbit, and an approximate size (about 1000 km, or 620 mi in diameter). For now, in picturing what the world is actually like, it is necessary to rely in part on the imagination (Fig. 1). With an apparent visual magnitude of about 21, Sedna is not particularly faint by the standards of objects thought to be closely related to it, located in the solar system's Kuiper Belt. Nevertheless, it is still so faint that detailed study is extremely difficult. Like many Kuiper Belt objects, Sedna is red in color, likely due to surface hydrocarbons being long exposed to solar radiation. Sedna is actually one of the reddest objects in the solar system, approaching Mars in hue. See also: Kuiper Belt; Magnitude (astronomy); Mars; Organic chemistry; Planet; Radiation; Solar system

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