Seems to me not. Only the fact that it has a moon and we’re reluctant to admit we made a mistake by calling it a planet in the first place, seems to be the only reason to keep it as a planet.
{{{Seems to me not. Only the fact that it has a moon and we’re reluctant to admit we made a mistake by calling it a planet in the first place, seems to be the only reason to keep it as a planet.}}}—Markxxx
On what basis would you discount Pluto from being considered a planet?
I’m not being confrontational, I’m just interested in seeing it from your point of view.
–Kalél
(The Original EnigmaOne)
Common ¢ for all ages.
Even though it appears as though it may have either been a moon of Neptune or an errant asteroid, it does have the requisites of being called a planet:
[ul][li]it has its own solar orbit, albeit eccentric;[/li][li]it’s of planetary size, smaller than most or all of the others, but larger than the asteroids of the Asteroid Belt between Mars and Jupiter;[/li][li]it has a moon.[/ul][/li]If it were in the asteroid belt, it might be called an asteroid. It would probably be smaller as well, being pummelled by its neighbors.
Ahem. I have a personal interest in this.
Pluto is much smaller than previously supposed and its composition is different than expected. The story of its discovery sounds like good, hard science but it turns out largely to be a fluke. Its orbit is so bizarre that it is sometimes assumed to be an escaped moon of Neptune.
In spite of all that, Pluto is still a planet, if for no other reason than historical precedence. For an excellent web page on the planet with some arguments for full planethood see <ref>http://dosxx.colorado.edu/plutohome.html </ref>
Briefly, if it’s large enough to be round (Pluto is, asteroids aren’t) and has its own orbit around the sun (Pluto does, the large moons of the outer planets don’t), then it’s a planet. I personally think the existence of a moon is another strong point in its favor.
The interesting thing is that Pluto is probably the largest and closest example of a newly defined class of object found in the solar system – distant, small and icy – called plutinos. The question about planethood arises partly because of the discovery of these objects. Some people insist it must be one or the other, planet or plutino, it can’t be both. I say, wotthehell! Whoever heard of a solar system with less than nine planets?
“non sunt multiplicanda entia praeter necessitatem”
The biggest argument for Pluto’s planethood is it’s size. Sure it’s small for a planet, but it has 5 times the mass of **ALL ** known asteroids **COMBINED **. Despite what someone said above, roundness isn’t a good measure, Ceres and several other asteroids are sperical. Nor is the presence of a moon-the asteroid Ida has a moon, Dactyl.
Pluto does have one thing that no other asteroid has, an atmosphere. It’s tenuous, but it’s detecable.
At any rate, a Working Group of the Small Bodiies Names Committee of the Division of Planetary System Sciences of the International Astronomical Union has decided against any change of the status of Pluto and I figure thay know more than we do.
Check out Nasa’s Much Ado about Pluto page for some details.
Jim Petty
An oak tree is just a nut that stood it’s ground
Don’t click here
Oh ,sure ,make Pluto a planet. Next thing you know there’s Mickey bangin on your door,then Bugs,even Daffy,now THERE’S an eccentric.
Hey! Pluto IS a planet. I know because I was born on the 50th aniversary of it’s discovery. It was discovered March 13, 1930, and I was born March 13, 1980. It is the only cool thing about my birth date, so Pluto is very important to me.
At least one person down here cares about you, Pluto :o)
(how’d I make that red face?)
Yeah, but are you being goofy?
your humble TubaDiva
Meditating on “Being and Goofiness.”
According to Bob Berman in his 1995 book Secrets of the Night Sky, Pluto is NOT a planet.
"Except, it isn’t a planet. Sure, most people will keep calling it one, out of habit. But since the discovery in the 1980s that it’s only half the size of the moon, we cannot really put it in the class of the other planets. It’s more like an asteroid, or minor planet, and it even travels in an odd, eccentric, non-planetary-type orbit.
“Nor is it an ‘it’–Pluto is a ‘they’! There are two of them! Pluto is a double object, two icy chunks orbiting each other every six days, the larger piece barely twice the size of the smaller. Perhaps Pluto represents the largest member of a new class of small asteroid-like objects that inhabit the outskirts of the solar system.”
Perhaps, but it’s way, way, to big to be an asteroid. It’s five times as massive as all the known asteroids put together. It’s 14.6 times as massive as Ceres, the most massive real asteroid. In fact Pluto’s moon, Charon is 2.4 times as massive as Ceres. It’s just not an asteroid.
There is also no chemical evidence that Pluto is a traditional asteroid. It is similar to Triton, Chiron and the Kuiper belt objects, and is therefore cometary. But even then, it’s way, way too big. Other than Pluto, Triton and Charon, all of questionable Kuiper Belt Object origin, the next largest KBO is 1996 TO66, which is MAYBE, AT MOST 740 KM in diameter. Not even as big as the asteroid Ceres. Much less Charon or Pluto.
The question of Pluto’s status remains up in the air, but few people are considering calling it an asteroid anymore. The whole study of trans-Neptunian objects is in it’s infancy and the status of Pluto may change, but it will become a menber of the Kuiper Belt Objects of some new class, not an asteroid.
Jim Petty
An oak tree is just a nut that stood it’s ground
Don’t click here
My question is why the moon is not a planet. The moon is outside the gravitational dominance of Earth and therefore not a satellite of Earth.
There is no safety for honest men but by believing all possible evil of evil men.
–Edmund Burke
Hrm? What do you mean by that? I would say that the gravitation of the Earth plays a pretty dramatic role in the path of the Moon…
The Earth and Moon are a system, in which the Earth is by far the dominant body. To me that suggests that the Moon is a moon (or natural satellite) rather than a planet.
I firmly believe in the natural right of self-determination.
Peace.
Perhaps, but if you back an astronomer into a corner, he’s probably going to state that the Moon is not a satellite of the Earth. For the following reason, posted for at least the 10th time between here and old the AOL board–
There is no doubt that the Moon goes around the Earth, but does it orbit it?
The formula for universal gravitation is- f=m1m2g/d^2
where m1 and m2are the masses of the respective bodies in grams, d is the distance in meters and g is the gravitational constant.
To calculate the Tug-of-War (TOW) value for a planet and its satellites you divide the pull of the planet on its satellite by the pull of the sun on the satellite. This gives you the following (where s stands for the Sun and p for the planet-TOW=mpds^2/(msdp^2)
Where mp stands for the mass of the planet, ms the mass of the sun, ds the distance from the satellite to the sun and dp, the distance of the satellite to the planet. This is a scalar value that gives the ratio. Note that the gravitation constant and the mass of the satellite do not matter .
So what are the Tug-of-War values for the satellites?
Satellite primary TOW
Moon Earth 0.46
Phobos Mars 206.94
Deimos Mars 31.69
Metis Jupiter 35302.72
Adrastea Jupiter 34757.51
Amalthea Jupiter 17655.13
Thebe Jupiter 11736.05
Io Jupiter 3247.90
Europa Jupiter 1284.64
Ganymede Jupiter 505.20
Callisto Jupiter 163.13
Leda Jupiter 4.70
Himalia Jupiter 4.39
Lysithea Jupiter 4.21
Elara Jupiter 4.20
Ananke Jupiter 1.29
Carme Jupiter 1.13
Pasiphae Jupiter 1.05
Sinope Jupiter 1.03
Pan Saturn 32478.29
Atlas Saturn 30622.78
Prometheus Saturn 30183.75
Pandora Saturn 28921.85
Epimetheus Saturn 25576.96
Janus Saturn 25576.96
Mimas Saturn 16856.87
Enceladus Saturn 10295.53
Tethys Saturn 6701.30
Telesto Saturn 6701.30
Calypso Saturn 6701.30
Dione Saturn 4103.18
Helene Saturn 4103.18
Rhea Saturn 2099.82
Titan Saturn 390.54
Hyperion Saturn 265.88
Iapetus Saturn 45.99
Phoebe Saturn 3.48
Cordelia Uranus 143810.30
Ophelia Uranus 123294.16
Bianca Uranus 103282.32
Cressida Uranus 93529.07
Desdemona Uranus 90583.46
Juliet Uranus 87774.84
Portia Uranus 82535.76
Rosalind Uranus 73372.60
Belinda Uranus 63915.69
Puck Uranus 48610.84
Miranda Uranus 21273.71
Ariel Uranus 9855.15
Umbriel Uranus 5081.21
Titania Uranus 1891.29
Oberon Uranus 1057.77
Caliban Uranus 9.99
Sycorax Uranus 5.62
Naiad Neptune 451356.02
Thalassa Neptune 415969.71
Despina Neptune 370211.56
Galatea Neptune 270531.81
Larissa Neptune 189905.82
Proteus Neptune 74685.74
Triton Neptune 8251.73
Nereid Neptune 34.22
Charon Pluto 557.93
Thus the Moon us unique in that it is the only satellite that is pulled by the sun more than by the its primary. It doesn’t really orbit the Earth by a strict definition.
Jim Petty
An oak tree is just a nut that stood it’s ground
Don’t click here
Sorry about the formatting back there, I guess I should have done this…
<BLOCKQUOTE><font size=“1” face=“Verdana, Arial”>code:</font><HR><pre>
Satellite primary TOW
Moon Earth 0.46
Phobos Mars 206.94
Deimos Mars 31.69
Metis Jupiter 35302.72
Adrastea Jupiter 34757.51
Amalthea Jupiter 17655.13
Thebe Jupiter 11736.05
Io Jupiter 3247.90
Europa Jupiter 1284.64
Ganymede Jupiter 505.20
Callisto Jupiter 163.13
Leda Jupiter 4.70
Himalia Jupiter 4.39
Lysithea Jupiter 4.21
Elara Jupiter 4.20
Ananke Jupiter 1.29
Carme Jupiter 1.13
Pasiphae Jupiter 1.05
Sinope Jupiter 1.03
Pan Saturn 32478.29
Atlas Saturn 30622.78
Prometheus Saturn 30183.75
Pandora Saturn 28921.85
Epimetheus Saturn 25576.96
Janus Saturn 25576.96
Mimas Saturn 16856.87
Enceladus Saturn 10295.53
Tethys Saturn 6701.30
Telesto Saturn 6701.30
Calypso Saturn 6701.30
Dione Saturn 4103.18
Helene Saturn 4103.18
Rhea Saturn 2099.82
Titan Saturn 390.54
Hyperion Saturn 265.88
Iapetus Saturn 45.99
Phoebe Saturn 3.48
Cordelia Uranus 143810.30
Ophelia Uranus 123294.16
Bianca Uranus 103282.32
Cressida Uranus 93529.07
Desdemona Uranus 90583.46
Juliet Uranus 87774.84
Portia Uranus 82535.76
Rosalind Uranus 73372.60
Belinda Uranus 63915.69
Puck Uranus 48610.84
Miranda Uranus 21273.71
Ariel Uranus 9855.15
Umbriel Uranus 5081.21
Titania Uranus 1891.29
Oberon Uranus 1057.77
Caliban Uranus 9.99
Sycorax Uranus 5.62
Naiad Neptune 451356.02
Thalassa Neptune 415969.71
Despina Neptune 370211.56
Galatea Neptune 270531.81
Larissa Neptune 189905.82
Proteus Neptune 74685.74
Triton Neptune 8251.73
Nereid Neptune 34.22
Charon Pluto 557.93
------------------
**Jim Petty
*An oak tree is just a nut that stood it's ground***
[Don't click here](http://hometown.aol.com/jimpetty/page/index.htm)Re the status of the Moon
Jimpy, point taken. Somehow I managed to miss all of the previous posts about that. Well, I skim, so I guess it’s bound to happen sometimes.
It seems that the normal definitions of orbit and satellite are a bit too vague to present their own conclusion to this.
For example, from EB:
*satellite
natural or artificial object that revolves around a larger astronomical
object, usually a planet.*
By this def, the Moon would be a satellite, unless the definition of “around” is limited, but that seems pretty dicey. I am not aware of a more technical definition of a satellite, but I’d be curious to here of such a definition if it existed.
It still doesn’t seem natural to me to call the Moon a planet in any case. Mebbe the minor partner in a binary planetary system, or some mumbo jumbo to that effect…
If humans had evolved on Mars, they’d probably consider Earth/Moon a double planet – the Moon is visible to the naked eye from Mars.
John W. Kennedy
“Compact is becoming contract; man only earns and pays.”
– Charles Williams