planet question?

Question

ok my first main question is about the new planet definition, recently the 2006 definition of a planet stated that it was a celestial body that:
is in orbit around the Sun,
has sufficient mass so that it assumes a hydrostatic equilibrium (nearly round) shape, and
has "cleared the neighborhood" around its orbit.
b/c of this and other reasons pluto is no longer considered a planet. I was wondering though why isn't neptune no longer considered a planet due to the fact that pluto's orbit intersects with neptunes stating that neptune has not 'cleared the neighborhood' around its orbit therefore not qualifying all three statements of a planet.

also on an aside note because Pluto's orbit intersects with Neptune's technically Pluto was the 8th planet in the solar system from 1979 to 1999 and Neptune was the ninth, did I just fall asleep in class and missed this? b/c I don't remember teachers telling me this....was that common teaching? or did they just leave that out as to not confuse us.

Answer 1

Neptune still is a planet. It was Pluto that was downgraded. you certainly must have fallen asleep, I taught it in my physics classes and you seem confused about Neptune even now. By your interpretation Earth wouldn't be a planet since objects pass through our orbit (comets and some asteroids) all the time.
I think the key concept to having cleared the neighborhood is being GRAVITATIONALLY DOMINANT. Obviously Neptune is NOT that when it comes to its effect on Pluto. Nor is the Earth that when it comes to its effect on comets and asteroids. You can deduce the rest.

Answer 2

Pluto is smaller than Neptune so it loses in 'clearing the neighborhood' (which of course is not absolute or none of the planets would qualify). Also, Pluto's orbit is highly inclined to the plane of all the other orbits as well as being so elliptical that it does cross (in the sense of getting closer to the Sun) Neptune's sometimes, but is still on average much farther away from the Sun than Neptune.

I am happy that Pluto was demoted because it's been an anomaly since it was discovered. It belongs with the other Kuiper Belt objects - some of which are bigger than Pluto - in the useful and more descriptive category of 'minor planet.'

Removing Pluto also restores the symmetry of the solar system to its previous four small inner rocky planets and four large outer gaseous planets all orbiting in the same plane in the same direction, sharing an obvious common origin.

Answer 3

You're right about the orbits crossing. Most textbooks don't bother to mention it. I took "Geology of the Planets" while in college, and that is when I officially was taught the crossover of Pluto and Neptune.

Pluto isn't actually an obstruction of Neptune's orbit. Neptune has an atmosphere and 9 moons. It's a gas planet similar to Uranus. The planet was hypothesized by scientists (notably Le Verrier) since Uranus was obviously being affected by another celestial body, changing what would ordinarily be a "perfect" orbit.

http://news.nationalgeographic.com/news/2006/08/060824-pluto-planet.html This site explains it the best: Neptune sweeps up any debris in its way, while Pluto does not. It has to DOMINATE its orbit. Pluto is considered a "dwarf planet" now, which means it is pretty large, but that it isn't large enough to attract other things to orbit it and it has not "cleaned up" its orbit like the other planets have.

http://starchild.gsfc.nasa.gov/docs/StarChild/solar_system_level1/neptune.html
http://solarsystem.nasa.gov/planets/profile.cfm?Object=Neptune&Display=Overview

Answer 4

As far as I know, Neptune is still a planet, according to NASA. The debate is not really at all over Neptune being a planet or not, it's about Pluto being a planet, dwarf planet, or other...Neptune is definitely the eighth planet and Pluto may/may not be the ninth planet...Depends on the debate over Pluto/Xena/ETC!!! You're probably right they left that out because teachers like to keep things simple for their students. Me of all people should know...lol

Answer 5

1. Primarily because Neptune is larger than Pluto. It would be considered the dominant planetary body in that area.

2. Pluto's orbit has been established for many, many years - since the time shortly after it's discovery. It was a fairly big deal (I remember the announcement on NBC News), stating the "order of the planets is going to shift tomorrow..."

Because of Pluto's highly eliptical - and being so far outside the planetary plane - it's okay with me to demote it to a "dwarf planet" status.

Answer 6

Pluto's orbit does NOT intersect with Neptune's. It is inclined at a steep angle and never crosses. Sometimes it is closer to the Sun than Neptune, but it does not cross Neptune's orbit to get there.

"Clearing the neighborhood" is a relative statement. No planet has completely cleared its orbit of debris. But Earth has cleared its orbit of Earth-like bodies, Neptune has cleared its orbit of Neptune-like bodies, but Pluto has not cleared its orbit of Pluto-like bodies.

Answer 7

good question.
researching.............What the HELL does neighborhood mean?
http://en.wikipedia.org/wiki/Cleared_the_neighbourhood
"The IAU's definition does not attach specific numbers or equations to this term"

"Stern, currently leading the NASA New Horizons mission to Pluto, objects to the reclassification of Pluto on the basis that—like Pluto—Earth, Mars, Jupiter and Neptune have not cleared their orbital neighbourhoods either. Earth co-orbits with 10,000 near-Earth asteroids, and Jupiter has 100,000 Trojan asteroids in its orbital path. "If Neptune had cleared its zone, Pluto wouldn't be there," he now says"


I thought "cleared the neighborhood" was the ONLY reason pluto was downgraded

Answer 8

all the books show that their orbits cross, that is common knowledge for people who read.