What Is Sedna?
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Sedna is a distant solar system body discovered in 2003, with one of the longest orbits ever observed at 10,500 years. It travels between 76 and nearly 1,000 AU from the Sun. Sedna may be the first observed inner Oort Cloud object. It's a dwarf planet candidate but not yet officially classified.
Sedna is one of the strangest objects in our solar system. Discovered in 2003, it orbits the Sun on an extraordinarily elongated path that takes 10,500 years to complete. At its farthest, Sedna is nearly 1,000 AU from the Sun, in the cold outer reaches where temperatures approach absolute zero. Sedna may be the first observed object from the inner Oort Cloud, a previously unseen region.
How was Sedna discovered?
Through a sky survey at Palomar Observatory. According to NASA, Sedna was discovered in November 2003 by Mike Brown, Chad Trujillo, and David Rabinowitz using the Palomar Observatory's Samuel Oschin telescope. The discovery was announced in March 2004. The object was found in one of the coldest known regions of our solar system. Sedna was named after the Inuit goddess Sedna, who created the sea creatures of the Arctic and lives at the bottom of the icy ocean, a fitting reference to its extreme distance from the Sun.
What's its orbit like?
Extremely elongated. Sedna travels in a highly elongated orbit, ranging from about 76 AU at perihelion (closest approach) to nearly 1,000 AU at aphelion (farthest distance). For comparison, Pluto's orbit ranges from 30 to 49 AU. Sedna takes about 10,500 Earth years to complete one orbit, longer than human civilization has existed. It's currently approaching its closest point to the Sun, which it will reach around 2076. After that, it will spend the next several thousand years moving back out into the extreme outer solar system.
Why is Sedna special?
It may be the first inner Oort Cloud object observed. Sedna's orbit never enters the Kuiper Belt (which extends to about 50 AU). Even at closest approach, Sedna is far beyond the Kuiper Belt. This led its discoverers to suggest that Sedna belongs to the inner Oort Cloud, a region only theorized previously. If true, Sedna offers the first chance to study an Oort Cloud object up close. It may also help explain how the Oort Cloud formed.
Is Sedna a dwarf planet?
Probably, but not yet officially. Sedna is large enough to be round under its own gravity (estimates put it at 600 to 1,000 km in diameter), meeting one criterion for dwarf planet status. The IAU has not yet officially classified it, in part because Sedna is so distant that confirming its size and shape is difficult. Many astronomers treat Sedna as a probable dwarf planet pending formal classification. The number of dwarf planet candidates in the outer solar system may eventually be in the hundreds.
Sedna is a distant solar system body discovered in 2003 with an extraordinary 10,500-year orbit ranging from 76 to nearly 1,000 AU from the Sun. It may be the first inner Oort Cloud object ever observed. Sedna is a probable dwarf planet pending formal classification. It's currently approaching its closest point to the Sun, expected around 2076, after which it will move outward again for millennia.
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