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View Full Version : Sedna - the 10th planet or not?


Darius Wey
03-22-2004, 06:57 AM
In case you've been 'out of this world', scientists discovered a supposed 10th planetary body about a week ago, which they've called Sedna.

It's three times further from Earth than Pluto is.

The question I'm asking is - do you think Sedna is a planet, or just some asteroid floating around?

c38b2
03-22-2004, 12:55 PM
Jupiter is a planet. Saturn is a planet. Sedna is not a planet. I don't think Pluto is either but because it has been considered a planet for so long it's only fair that it retains it's planetary status.

Talldog
03-22-2004, 01:25 PM
Isn't there a minimum size to be designated a planet? Calculations so far suggest that Sedna is, at most, 1,000 miles in diameter. That's half the diameter of Pluto.

rhmorrison
03-22-2004, 01:48 PM
Based on the dictionary definitions of a Planet SEDNA could be either one that is why astronomers are going to meet to nail down the definition of a planet and decide whether Senda is the 10th planet or a permantly orbiting asteroid.

IMHO it is a planet albeit a very small one...

plan·et ( P ) Pronunciation Key (plnt)
n.
A nonluminous celestial body larger than an asteroid or comet, illuminated by light from a star, such as the sun, around which it revolves. In the solar system there are nine known planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto. One of the seven celestial bodies, Mercury, Venus, the moon, the sun, Mars, Jupiter, and Saturn, visible to the naked eye and thought by ancient astronomers to revolve in the heavens about a fixed Earth and among fixed stars. One of the seven revolving astrological celestial bodies that in conjunction with the stars are believed to influence human affairs and personalities.--------------------------------------------------------------------------------
Middle English, from Old French planete, from Late Latin planta, from Greek plants, variant of plans, plant-, from plansthai, to wander. See pel-2 in Indo-European Roots.


planet

\Plan"et\, n. [OE. planete, F. plan[`e]te, L. planeta, fr. Gr. ?, and ? a planet; prop. wandering, fr. ? to wander, fr. ? a wandering.]

1. (Astron.) A celestial body which revolves about the sun in an orbit of a moderate degree of eccentricity. It is distinguished from a comet by the absence of a coma, and by having a less eccentric orbit. See Solar system.

Note: The term planet was first used to distinguish those stars which have an apparent motion through the constellations from the fixed stars, which retain their relative places unchanged. The inferior planets are Mercury and Venus, which are nearer to the sun than is the earth; the superior planets are Mars, the asteroids, Jupiter, Saturn, Uranus, and Neptune, which are farther from the sun than is the earth. Primary planets are those which revolve about the sun; secondary planets, or moons, are those which revolve around the primary planets as satellites, and at the same time revolve with them about the sun.

Robb Bates
03-22-2004, 03:38 PM
I figure, if it has enough mass to create enough gravity to make itself round, as opposed to some irregular lumpy shape, and has a nice semi round orbit, why not call it a planet.

There is also some kind of equation that you can use to figure out where planets "should" be. All the existing planets, except pluto, but including the asteroid belt (which could have been a planet at one time) work with this equation. I wonder if Sedna does.

Robb

Jeff Rutledge
03-22-2004, 05:44 PM
I'm not a scientist by any stretch, but to me a planet maintains an orbit around the sun, just as a moon orbits a planet. I'm probably over simplifying it, but that's what qualifies to me.

Robb Bates
03-22-2004, 05:56 PM
Yes, but comets orbit the sun, as does the asteroid belt. But they're not planets. I think it's all about the size of the thing and definitely some politics going on. "What? ten planets? no way, there have always been nine!"

Robb

Jeff Rutledge
03-22-2004, 06:07 PM
Good points. Like I said, I figured I was over simplifying it. :D

Pat Logsdon
03-22-2004, 06:24 PM
I think the main determining factor will probably be whether it's classified as a "Kuiper Belt Object". This is a ring of icy objects that orbit the sun beyond Neptune.

There are some who think that Pluto is a Kuiper Belt Object, which is why we've had the debates in recent years about whether Pluto is a planet.

In my opinion, it's a planet if it's a) at least Pluto size or larger, and in a fairly stable orbit around the sun, or b) got a satellite. While Pluto has a highly eccentric orbit (it's sometimes inside the orbit of Neptune), it does have a satellite. If Sedna has an orbit like Pluto's, and it does NOT have a satellite, I don't think it should be classified as a planet.

This was also debated a few years ago when Quaoar (http://science.nasa.gov/headlines/y2002/07oct_newworld.htm) was discovered.

Kati Compton
03-22-2004, 07:11 PM
I think it's all about publishers wanting to make new textbooks and schools not wanting to have to buy them... ;)

Dave Potter
03-22-2004, 08:12 PM
I think it's all about publishers wanting to make new textbooks and schools not wanting to have to buy them... ;)


Hmmmm... Good point!

Jason Dunn
03-22-2004, 08:35 PM
The interesting thing to me isn't so much whether or not this is a planet, but once again reinforces my belief that as humans, we have such a limited grasp of the universe...there are so many things beyond our understanding, yet we arrogantly assume that science has every answer we every need. I'm a fan of science and pushing the boundaries of human understanding, but we should always do it with humility. ;-)

Mitch D
03-23-2004, 03:26 AM
I voted that it is a planet but I think there should have been another option. THat option might have read something like "I/We don't have enough data to make such a determination".

I, like many others, am excited to think that another planet was discovered in my lifetime. But I still think that our ability to study the universe is not advanced enough to be certian beyond a reasonable doubt that Sedna is indeed anything more than a large object floating in space.

I personally think it'll be years and years before we can say for certian than just what Sedna is.

But that's just my two cents worth

hollis_f
03-23-2004, 08:26 AM
'Planet' is a human concept. It's symptomatic of our need to categorise everything. It's now getting obvious that there's a continuous range of sizes of bodies orbiting the Sun - from tiny grains of dust to Jupiter. But us humans don't like continuous shades of grey - we like things black or white, so we can pretend we understand things because we know which box to put them in.

Whether Sedna is a planet (or Pluto, or Quaoar, or Ceres, or Mercury, or 2002FH) depends on where us humans draw that artificial line. Then we can give all those bodies their little labels and pretend we understand them.