sedna
Proper noun A trans-Neptunian object, classified as a dwarf planet candidate, composed primarily of rock and ice. It was discovered in 2003 and is notable for its extremely distant and elongated orbit around the Sun.
"Sedna" is used as a proper noun to refer specifically to this celestial body. It is always capitalized.
- Astronomers were amazed by the discovery of Sedna due to its vast distance from the Sun.
- The orbit of Sedna takes approximately 11,400 Earth years to complete.
- Sedna is one of the most distant known objects in our solar system.
- In astronomical context: The name "Sedna" is formally designated as (90377) Sedna. It is often discussed in relation to the Oort cloud, a theoretical shell of icy objects at the solar system's edge.
- The peculiar orbit of (90377) Sedna provides clues about the early history of the solar system.
- Sednoid (noun): A class of trans-Neptunian objects with similar orbital characteristics to Sedna (extremely distant, with a high perihelion).
- Astronomers are searching for more sednoids to understand their origin.
- (90377) Sedna: The formal astronomical designation.
- Distant planetoid: A descriptive term highlighting its classification and location.
- Trans-Neptunian object (TNO): A broader category of objects orbiting the Sun beyond Neptune, which includes Sedna.
While the provided reference context describes Sedna as "a planetoid... about three-quarters the size of Pluto," current astronomical classification is more precise. Key characteristics include: 1. Orbital Characteristics: It has one of the most distant and elongated orbits known, with its closest approach to the Sun (perihelion) still being far beyond Neptune. 2. Physical Composition: It is an icy body, likely covered with a mixture of water, methane, and nitrogen ices over a rocky core. 3. Discovery Significance: Its discovery challenged existing models of the solar system's structure and hinted at the existence of the inner Oort cloud.
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a planetoid of rock and ice about three-quarters the size of Pluto discovered in 2003; the most distant object known to orbit around the sun
