Sedna

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Introduction1

Encyclopedia

90377 Sedna is a large minor planet in the outer reaches of the Solar System that was, as of 2015, at a distance of about 86 astronomical units (1.29×1010 km; 8.0×109 mi) from the Sun, about three times as far as Neptune. Spectroscopy has revealed that Sedna’s surface composition is largely a mixture of water, methane, and nitrogen ices with tholins. Its surface is one of the reddest among Solar System objects. It is most likely a dwarf planet. Among the eight largest trans-Neptunian objects, Sedna is the only one not known to have a moon.

For most of its orbit, it is even farther from the Sun than at present, with its aphelion estimated at 937 AU (31 times Neptune’s distance), making it one of the most distant-known objects in the Solar System other than long-period comets.

Sedna has an exceptionally long and elongated orbit, taking approximately 11,400 years to complete and a distant point of closest approach to the Sun at 76 AU. These facts have led to much speculation about its origin. The Minor Planet Center currently places Sedna in the scattered disc, a group of objects sent into highly elongated orbits by the gravitational influence of Neptune. This classification has been contested because Sedna never comes close enough to Neptune to have been scattered by it, leading some astronomers to informally refer to it as the first known member of the inner Oort cloud. Others speculate that it might have been tugged into its current orbit by a passing star, perhaps one within the Sun’s birth cluster (an open cluster), or even that it was captured from another star system. Another hypothesis suggests that its orbit may be evidence for a large planet beyond the orbit of Neptune.

Astronomer Michael E. Brown, co-discoverer of Sedna and the dwarf planets Eris, Haumea, and Makemake, thinks that it is the most scientifically important trans-Neptunian object found to date, because understanding its unusual orbit is likely to yield valuable information about the origin and early evolution of the Solar System. — Wikipedia

Encyclopædia Britannica

Search

WolframAlpha

Library

WorldCat, Library of Congress, UPenn Online Books, Open Library

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Participation

Education

Planets and Dwarf Planets (Ask an Astronomer, Cornell University)

Organization

International Astronomical Union (IAU)
Minor Planet Center (International Astronomical Union)

News

Phys.org, NPR Archives

Book

ISBNdb

Government

Document

USA.gov

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  • Still searching for Planet 9
    on March 14, 2022 at 4:50 pm

    The solar system has eight planets. In 2006, astronomers reclassified Pluto as a dwarf planet, the same class that contains Eris, Sedna, Quaoar, Ceres and perhaps many more solar system small bodies. These are defined approximately as bodies that orbit the sun but that are not massive enough (unlike regular planets) to gravitationally dominate their environments by clearing away material. Astronomers wonder, though, whether there might not really be a ninth planet previously undiscovered but […]

  • 2029 will be the perfect year to launch a mission...
    on January 5, 2022 at 11:13 am

    Object 90377 Sedna—a distant trans-Neptunian object known best for its highly elliptical, 11,390-year long orbit—is currently on its way toward perihelion (its closest approach to the sun) in 2076. After that, Sedna will swing out into deep space again and won't be back for millennia, making this flyby a once-in-a-lifetime (or, once in ~113 lifetimes) opportunity to study an object from the far reaches of our solar system. There are no missions to Sedna in the works just yet, but […]

  • Astronomers confirm orbit of most distant object...
    on February 10, 2021 at 7:00 pm

    A team of astronomers, including associate professor Chad Trujillo of Northern Arizona University's Department of Astronomy and Planetary Science, have confirmed a planetoid that is almost four times farther from the Sun than Pluto, making it the most distant object ever observed in our solar system. The planetoid, which has been nicknamed "Farfarout," was first detected in 2018, and the team has now collected enough observations to pin down its orbit. The Minor Planet Center has now given it […]

  • NASA's Webb to examine objects in the graveyard...
    on October 29, 2020 at 1:04 pm

    Beyond the orbit of Neptune, a diverse collection of thousands of dwarf planets and other relatively small objects dwells in a region called the Kuiper Belt. These often-pristine leftovers from our solar system's days of planet formation are called Kuiper Belt objects, or trans-Neptunian objects. NASA's upcoming James Webb Space Telescope will examine an assortment of these icy bodies in a series of programs called Guaranteed Time Observations shortly after its launch in 2021. The goal is to […]

  • The collective power of the solar system's dark,...
    on July 7, 2020 at 3:01 pm

    The outermost reaches of our solar system are a strange place—filled with dark and icy bodies with nicknames like Sedna, Biden and The Goblin, each of which span several hundred miles across.

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Related

Here are links to pages about closely related subjects.

Knowledge Realm

Physical

“Fundamentals”
Law (Constant) Relativity
Force Gravity, Electromagnetism (Light, Color)
Matter (Microscope) Molecule, Atom (Periodic Table), Particle

“Space”
Universe (Astronomical Instrument)
Galaxy Milky Way, Andromeda
Planetary System Star, Brown Dwarf, Planet, Moon

Our Neighborhood
Solar System Sun
Terrestrial Planet Mercury, Venus, Earth (Moon), Mars
Asteroid Belt Ceres, Vesta
Jovian Planet Jupiter, Saturn, Uranus, Neptune
Trans-Neptunian Object
Kuiper Belt Pluto, Haumea, Makemake
Scattered Disc Eris, Sedna, Planet X
Oort Cloud Etc. Scholz’s Star
Small Body Comet, Centaur, Asteroid

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Notes

1.   The resources on this page are are organized by a classification scheme developed exclusively for Cosma.