So-called 10th planet is larger than Pluto

www.foxnews.com...

I wish scientists would come up with a definition for a planet considering all the turmoil this has caused. I can, however, understand how it could be something of ambiguity.

What do you guys think should be some guidelines for the definitive answer to question of what is a planet?

I like the idea of a planet having:
1. an atmosphere
2. some sort of surface activity
3. maybe the idea of smaller masses orbitting it (moon)

[edit on 1-2-2006 by Cephas]

[edit on 1-2-2006 by Cephas]

IMO I would look at other factors to determine if something is a planet or not. I think having an atmosphere is not a good requirement seeing how our own mercury has none. Surface activity is irrelevent (just my opinion) and moons... I think we can't go by that either. Mercury and Venus have no moons.

What does constitute a planet?

I think first off that it must be orbiting a sun and be in its own orbit. To clarify, I think that anything orbiting within a belt of asteroids cannot be included as a planet. This includes the Kuiper Belt and this larger than Pluto "Xena". So I am also saying that I don't think Pluto should be classified as a planet since it is also in the Kuiper belt.

I think a second factor should be gravity. I think that the gravity of the orbiting mass should be great enough to pull the object into itself thus creating a spherical shape.

Here is another article on this "Xena" from discovery news
dsc.discovery.com...

BTW, I don't like the name Xena; who comes up with these names?

Originally posted by Archerette
...the name Xena; who comes up with these names?

to answer my own question, The IAU names 'em. IAU = International Astronomical Union, made up of astronomers worldwide, est. 1919.

From what I understand, they get the names for new celestial bodies from long-standing traditions and/or the names are founded in history, like mythology. That would explain the name Xena, but the news articles I read are not pointing to any real historical myth, but to the much more recent television show "Xena the Princess Warrior". That's just wrong. Yet another example of media misleading readers.

Originally posted by Archerette
IMO I would look at other factors to determine if something is a planet or not. I think having an atmosphere is not a good requirement seeing how our own mercury has none.

Mercury actually has a very thin atmosphere consisting of atoms blasted off its surface by the solar wind. Because Mercury is so hot, these atoms quickly escape into space. Thus in contrast to the Earth and Venus whose atmospheres are stable, Mercury's atmosphere is constantly being replenished.

Taken from here.

'Xena' is simply a nickname, the planet hasn't been officially named yet. I think I read that the discovers thought there ought to be a planet of that name, so started using it in the hope it'd lead to official acceptance....

At least it's easier to pronounce that Quaoar!

Here are some of the qualities I think a "planet" should have; this is based from a conversation I had at school just today, actually.

1) atmosphere - this would ensure a certain minimum gravity; even our smallest planets - Mercury and Pluto - have atmospheres.
2) be over a certain minimum size (not sure what that size would be, though)
3) orbit the sun in a regular pattern, even if a strange pattern like Pluto. This also disqualifies large objects like Ganymede or Titan that are bigger than some planets, but do not orbit the sun directly, being moons.
4) should be a (roughly) spherical object, disqualifying most asteroids, for example.

I don't think a planet should necessarily have to have a moon. Mercury and Venus are universally considered planets, and they have no moons.

The Ganymede moon is far bigger than Pluto, and if it was pulled out of Jupiter's orbit and placed where Pluto is, it would be considered a planet too.

If orbit is your deciding factor, it all depends on how strong a star's gravity is, and how strong the gravity of any gas giants. For example what would be a planet somewhere, would be a moon somewhere else.. and vice versa.

Well it wasn't until 1998 that Pluto was declared a planet officially, 30 years after it was discovered to have a moon by Astronomer James Christy in 1968. SO what makes a planet? It all depends on your definition.

From the article anyway, it looks like the big contention is, in addition to the size of the object, whether or not it is part of a larger system:

When the largest asteroids, Ceres, Vesta and Pallas, were discovered in the early 19th century, they were counted as planets until it became clear that they were part of a much larger belt of large rocks and planetoids ringing the Sun between Mars' and Jupiter's orbits.

Likewise, Pluto and Quaoar are part of the Kuiper Belt, an even larger ring of small objects orbiting the Sun beyond Neptune.

Ceres, Vesta, and Pallas are all good names for a planet. Quaor, etc are poor names. The vast majority of planets are named after greco-roman gods, from classical mythology. Anything with actual real religious connotations, like the gods of native american and inuit tribes, should be avoided, unless anyone wants a 'Planet Jesus" anytime soon.

Wasn’t their once thought a planet that orbited two stars or was in two solar systems?(like a figure eight, it went into one solar system and did a semi-circle then went into the other and did another semi-circle)Maybe I dreamt that I don’t know but I could have sworn that i remembered something of that nature?

[edit on 17-2-2006 by spaceman16]

Pluto isn't a planet........but it clearly is not a chunk of ice either as it is spherical with moons atmosphere and seasons etc etc

A planet has to exist in its own sphere of influence without similar objects nearby. therefore pluto fails as there are many kuiper belt objects.

The "asteroid" Ceres is large enough to be a planet and was for a while. Just unlucky it happens to be in the asteroid belt so it was demoted

as Pluto will be eventually. Triton was probably the 10th planet (imho)

To be honest, you cannot say the Kupier Belt Objects are not planets. I consider anything a planet, however... I have a list.

Anything smaller than our moon should be considered a Minor Planet if they are round/oval and have atleast ONE of the following:
Has a smaller to equal sized moon and is not a moon.
Has its own stable orbit seperate away from larger masses asides Solaris (eg: not an erradict orbit that may send it into the sun)

Anything larger than our Moon, Luna... but smaller than twice the size of Earth, should be considered a Typical Planet and atleast one of the same rules as above.

Anything larger than 2x the size of Earth and smaller than Jupiter should be considered a Major Planet (this includes 'super earths') and atleast one of the same rules as above.

Anything larger than Jupiter should be considered a Super Planet. Regardless of rock, gas, or what ever.


Thats how I classify my planets. So that counts even little Sedna in her giant orbit around Solaris. Anything that is stable, spherical planet in a clean circular or oval orbit, is considered a planet to me.

People who say "The objects in Kupier belt are not planets because they are in the belt."

Look at Sedna, its in a massive oval orbit, kupier belt is in a circular field. Thus Sedna is free moving of the belt. Also, if you clasify planets that are in belts as just large chunks of belt rock... then you would have to say "that planet in this other star system, 2x's the size of jupiter, within an asteroid field... is not a planet! But a solid, giant rock!" Realise, just because its a planet, doesn't mean it doesn't clip through asteroid fields! (Sucks for anyone building a base there though!)

Thats how I categorise planets, and I always will.

Originally posted by Foxe

Anything larger than Jupiter should be considered a Super Planet. Regardless of rock, gas, or what ever.

Aha! I've got you now! What about 'brown dwarves' then? Super Planet or failed star?

Well, you could theorecticly have a pure energy planet, with energy beings and energy birds and little energy babies.... but if you over look that, the question is. Is it orbitting another object? If so then one COULD consider it a planet, but I would stick with Binary Star System... unless the only object its orbit was around, was galactic center.

Hah back to you! Good sir

[edit on 18-3-2006 by Foxe]

Pluto to most is considered a planet but to many it is a comet as it has all the characteristics of a comet. Technically it is just a comet.

Except Comets don't have moons! It is a planet, it was declared a planet in 1998, sorry people, it may take 7 hours at the speed of light to get there, but it is a planet!

Originally posted by DevinS
Except Comets don't have moons! It is a planet, it was declared a planet in 1998, sorry people, it may take 7 hours at the speed of light to get there, but it is a planet!

Ha! I've got you now!

Astronomers Find Moon Orbiting Asteroid

For the first time ever, an Earth-based telescope has captured images of a small moon orbiting an asteroid.

Using the 12-foot (3.6-meter) Canada-France-Hawaii Telescope on Hawaii's Mauna Kea volcano, astronomers have discovered and photographed a satellite circling the asteroid Eugenia.

Some 133 miles (215 kilometers) in diameter, the oblong Eugenia is among the 25 largest bodies in the asteroid belt between Mars and Jupiter. Its moon is just 8 miles (13 kilometers) across, and orbits its spinning parent once every four and a half days at a distance of 745 miles (1,200 kilometers) from Eugenia, its discoverers say.

So if having a moon(s) is the criteria, then would you consider this asteroid a planet then?

Don't forget Ida and Dactyl.



I think the big deal about that article, Beachcoma, was that "For the first time ever, an Earth-based telescope has captured images..."

That being said, I would really like to know what people would even THINK to consider Pluto to be a comet.

Originally posted by cmdrkeenkid
I think the big deal about that article, Beachcoma, was that "For the first time ever, an Earth-based telescope has captured images..."

Yeah

The thing is I forgot what the names of those asteroids were, so I just did a Google on "asteroid orbiting asteroid" and that article came up.

Edit: I wouldn't consider Pluto a comet, but with more and more evidence coming in, I would categorize it as one of the Kuiper Belt Objects.

Now if Pluto were to be knocked off it's orbit and hurtle towards the center of the Solar System, developing a tail in the process, then maube I would start calling it a comet

[edit on 23-3-2006 by Beachcoma]

Originally posted by Beachcoma
The thing is I forgot what the names of those asteroids were, so I just did a Google on "asteroid orbiting asteroid" and that article came up.

Use the Google, Luke. Trust your feelings.

(Couldn't resist )

Now if Pluto were to be knocked off it's orbit and hurtle towards the center of the Solar System, developing a tail in the process, then maube I would start calling it a comet

I don't know about that, even. Technically speaking, Venus has a tail. A fair amount of its atmosphere gets blown off by Solar Wind and CMEs all the time. Some people think that this leads to flu outbreaks, even.

[edit on 3/23/2006 by cmdrkeenkid]