Why is Sedna not considered a planet?

Question

Sedna has cleared out it's own orbital path and is spherical in shape. With all this news about Pluto no longer being a planet, why is Sedna not considered a planet?

Answer 1

Sedna hasn't cleared out its orbital path - it is part of a swarm of objects collectively called the Kuiper Belt (kinda like the asteroid belt except made of icy bodies instead of rocky ones).

Answer 2

Sedna, named unofficially after the Inuit goddess of the sea, is the latest in a string of icy objects approaching the size of Pluto discovered in the outer reaches of the Solar System.

Sedna is believed to be about three-quarters of the size of Pluto, based on measurements of light reflected from its surface detected by telescopes on Earth.


Distant and faint, Sedna is causing a stir
Many astronomers, including Mike Brown of the California Institute of Technology, who led the team that discovered Sedna, admit it is not a true planet, preferring to describe it as a planetoid - somewhere between a planet and an asteroid.

But like other objects found in recent months that inhabit the band of cosmic debris beyond the Inner Solar System, the Kuiper Belt, it is much bigger than a typical asteroid.

Some believe it is only a matter of time before another such body is found which dwarfs Pluto.

Reclassifying Pluto is one way to solve the dilemma. When it was discovered in 1930 it was thought to be much bigger - and thus more planet-like - than it really is.

However, the astronomical community will not take kindly to the idea of downgrading Pluto's status. The last time it was suggested, in 1999, it caused an uproar.

Answer 3

This is the official criteria for being a planet:
A planet is anything in the heavens that's massive enough for its own gravity to keep it roughly round, that orbits a star on its own and is not a satellite, and that has cleared away any loose cosmic rubble from its neighborhood.

There are a couple of possibilities:
1) Pluto is considered a dwarf planet, and Sedna is smaller than Pluto.
2) There is a belief that the Oort Cloud, where Sedna is, will eventually be discovered to be full of small Knuiper Belt-type and sized objects.

A good site about Sedna is:
http://www.gps.caltech.edu/~mbrown/sedna/

Answer 4

Because Astronomers are afraid every dick, tom, and tracy will be allowed as a planet in our solar system. The term planet is arbitrary. We couldn't see very many before recent technology; but not we can discover maybe hundreds of objects that could easily be classified as planets by more traditional terms, therefore making the term quite insignificant. They dealt with the same thing in the early 19th century after the Ceres asteroid/dwarf planet was discovered and originally given the title of planet. Soon after, they discovered many many other ball shaped asteroids between the space of Mars and Jupiter and realized planet discovery would get out of hand; therefore they quickly demoted Ceres. The Kupiter belt has far more objects, many possibly larger than Pluto (as "Xena" is) so they would end up with an unrelenting problem of constant Planet discovery. This would then ask the question, okay, how then do we still recognize the original eight as significant? Actually, if they formalize the term "Dwarf Planet," then in one sense, Sedna would be at least a kind of planet, just not the "regular" kind, (still creating some confusion....) My vote would have been to make it the 10th, wait, 11th, wait, 12th, wait, 13th, wait....planet. But people don't generally care what musicians think about this issue.

Answer 5

Sedna's orbit must be a bit ecentric like Pluto.being in the oort cloud,It's size is small and is not acceptable as a planet.It has been counted as a Dwarf planet in which pluto,celes and Xena are categoried.Due to the lack of size Its gravitational force is also less.ASU(astronomical science Unit) considers that an orbit does not tell that is the planet a Real, actual Planet or not?It considers that some approximate size should be there and its gravity should be nor too less nor too more.

Answer 6

pluto is no longer a planet because it is believed to be just a comet-like ball of ice with an orbit


never heard of sedna shame on me

Answer 7

Sedna does not have enough powerful lobbyists to get the support it needs. The representatives that Sedna has sent have been highly ineffective in gathering any political support for their agenda. Yeah, that's it.

Answer 8

Pluto has an orbital path and a spherical shape, but was removed from planetary status. Same reason I guess.

Answer 9

It is the will of the Gods