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Sedna, Eris and Buffy

The image above is an artist's impression of Sedna.
"Sedna" is the official name of, "2003 VB12". Its been hypothesized that Sedna has a small moon in orbit around it.
At least 50% of Sedna's surface is formed from different ices, a mixture of methane, methanol and nitrogen.
Its diameter is at most 1800km, much smaller than Pluto.
At perihelion (closest point to Sun in its orbit) in 70 years it will be just 76AU (76 times the distance from the Earth to the Sun) from the Sun. That's twice as far as Pluto. (At aphelion, furthest from the Sun, its 900AU.)
It takes this small red planetoid around 10,500 years to orbit the Sun.
Its so distant that if you stood on its surface, you could block out the entire Sun with the head of a pin held at arm's length.
Sedna is believed to be a member of the Oort cloud (see "Oort Cloud" topic page).
Sedna was officially discovered in march 2004.
It was discovered by, Mike Brown (Caltech), Chad Trujillo (Gemini Observatory), and, David Rabinowitz (Yale University).
"Sedna" is named after the Inuit goddess who rules over the seas.

Formally nicknamed, "Xena", Eris is the official name of the planetoid, "2003 UB313" which was discovered by the same team who discovered Sedna. The official discovery was made on january 5th 2005, from plates taken in october 2003.
Eris (pronounced ee-ris) was the Greek goddess of discord and strife.
Mike Brown, who discovered Eris, suggested the name, "Eris" to the International Astronomical Union, because the Goddess created all sorts of problems by causing people to quarrel among themselves.
At the wedding of the parents of the Greek hero Achilles, all the gods were invited except her, and angered by her exclusion she spitefully caused a quarrel that led to the Trojan War.
The name seems quite apt considering all the trouble the dwarf planet has caused for Pluto!
The astronomers behind the discovery decided upon "Xena" for several reasons. All of the names of the other planets are named after male deities (the team wanted a female name). They first decided upon "Persephone" but there's already an asteroid by that name. Also, the astronomer Percival Lowell predicted that a large planet laid beyond the orbit of Pluto. He nicknamed this hypothetical planet, "Planet X", which is why the team chose upon the name beginning with an "X".
Of course this "Xena" in question is named after "Xena Warrior Princess" from the television programme of the same name.
Eris has been found to have a companion moon in orbit around it which had been nicknamed, "Gabrielle", after Xena Warrior Princess's companion in the tv show.
It has now been given the name, "Dysnomia", who in Greek mythology is the daughter of Eris, and the spirit of lawlessness.
Eris is the most distant object ever detected to be in orbit around the Sun.
It is almost 10 billion miles from the Sun. That's more than three times more distant than Pluto.
Eris is much bigger in diameter than Pluto, its diameter is somewhere in the region of 2400km.
Eris is covered with solid frozen methane. Its surface appears to be white. It reflects 86% of the sunlight that falls upon it. Thats more than any other body in the solar system other than Saturn's moon, Enceladus.

2004 XR190 or, "Buffy", orbits beyond Neptune in a circular orbit at a distance of 58AU and its orbit is highly tilted at a massive 47 degrees.

There's also been some other Kuiper Belt Objects discovered which too have been given unofficial nicknames. They are, "2003 EL61" with the nickname, Santa (which has a moon nicknamed Rudolph).
2003 EL61 is a large, dense, rugby-ball-shaped hunk of rock with a fast rotation rate.
Professor Mike Brown has calculated that the object could be due a close encounter with the planet Neptune.
If so, Neptune's gravity could catapult it into the inner Solar System as a short-period comet.
"2005 FY9" nicknamed Easterbunny.

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