Pluto Could Lose Planet Status

PhysOrg.com ^ | 21 June 2006 | Staff

[PatrickHenry]

At its conference this August, the International Astronomical Union (IAU) will make a decision that could see Pluto lose its status as a planet.

For the first time, the organisation will be officially defining the word "planet", and it is causing much debate in the world of astronomy.

There is only one thing that everyone seems to agree on: there are no longer nine planets in the Solar System.

The debate has been brought to a head by the discovery of a potential 10th planet, temporarily named 2003 UB313 in January 2005. This new candidate planet is bigger than Pluto.

The question now facing the IAU is whether to make this new discovery a planet.

Pluto is an unusual planet as it is made predominantly of ice and is smaller even than the Earth's Moon.

There is a group of astronomers that are arguing for an eight-planet SolarSystem, with neither Pluto or 2003 UB313 making the grade as a planet; but a number of astronomers are arguing for a more specific definition of a planet.

One of these; Kuiper Belt researcher Dr Marc Buie, of the Lowell Observatory in Arizona, has come up with a clear planetary definition he would like to see the IAU adopt.

I believe the definition of planet should be as simple as possible, so I've come up with two criteria," he said.

"One is that it can't be big enough to burn its own matter - that's what a star does. On the small end, I think the boundary between a planet and not a planet should be, is the gravity of the object stronger than the strength of the material of the object? That's a fancy way of saying is it round?"

This definition could lead to our Solar System having as many as 20 planets, including Pluto, 2003 UB313, and many objects that were previously classified as moons or asteroids.

One possible resolution to the debate is for new categories of planet to be introduced. Mercury, Venus, the Earth and Mars would be "rocky planets". The gas-giants Jupiter, Saturn, Uranus and Neptune would be a second category.

Whatever the outcome of this debate there is only one thing that we can be certain of; by September 2006 there will no longer be just nine planets in our Solar System.

[UnbelievingScumOnTheOtherSide]

I define a planet as anything Pluto or bigger that directly orbits a star.

Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
Pluto
"Uebee"

[Tanniker Smith]

Okay, you tell her that she's being demoted.

[aMorePerfectUnion]

Plutism - plain and simple! Those bloody Plutists!!!

We need special planetary districts to guarantee representation of minority planets.

[pleikumud]

How about Goofy? (Kerry comes to mind.)

[DannyTN]

Both definitions seem vague to me.

Re: star vs planet
if we think it's big enough to burn it's on matter, but isn't doing so? What if it's doing so but only on a very limited basis and doesn't look like a star?

Re: small end of planet
How round is round? We have mountains, does that mean our gravity isn't stronger than our material? Does an asteroid of fine particles that assumes a round shape qualify as a planet?

I think on the small end they should set a specific mass. On the large end, it should not be burning it's own material and it should be orbiting something.

What do we call a planet that's not orbiting a star? Is it still a planet?

[MortMan]

(5 things you can't have too much of: sex, money, firewood, guns and ammunition.)

I like your tagline, but you forgot horsepower.

Obviously, you've never tried to drive a 2WD truck up a steep hill on bald tires in the middle of winter... There IS such a thing as too much horsepower!!! ;-P

[Sacajaweau]

The only thing I learned that sticks in my head is: Stars twinkle, planets do not.

[Sloth]

Interesting. Both Titan and Ganymede are larger than the planet Mercury...

[DannyTN]

That's not too much horsepower, that's a baldness problem.

I was thinking balls could get added to that list, but then some guys have more balls than brains, and that's not good.

[Sacajaweau]

I have an VERY old USA atlas. There are several planets named and shown in their orbits besides what we learned in school.

[Sacajaweau]

Yeh....For streaking!!

[ABG(anybody but Gore)]

I can see the headline in the NY Times: Pluto Stripped of Planetary Status; Women and Minorities Most Affected

[dc27]

Reminds me of a time I towed my friend's ski boat with my 2WD truck. His 4WD was in the shop. All was good going down his steep driveway, which wasn't paved. It was just covered with crushed rock. Had to let all the air out of the tires and put bags of concrete in the bed to get up the driveway. It wasn't pretty, resembled a tractor pull. He wasn't too happy about all the rocks bouncing off his gel coat.

[cynicalman]

I was dated a women, in college, who thought there were only 7 planets in the entire universe. 35 years later my friend, who sent me up with this blind date, still refers to her as "7 planet women". Maybe she was just ahead of her time.

[cynicalman]

i was = I once

[cynicalman]

sent = set god I have to drink my cup of coffee before posting

[Maurice Tift]

Pluto not a planet!!! This is terrible!

Just yesterday, someone asked me if Goofy was really a dog?

[<1/1,000,000th%]

The 10th planet is nicknamed Xena until it is officially named.

Unfortunately, 2003 EL61 doesn't have a name yet.

[Gorjus]

I define a planet as anything Pluto or bigger that directly orbits a star.

Actually, if you look at the orbit, "our" moon actually orbits the sun, not Earth. The moon's orbit is always concave toward the sun. Sometimes (once each month) the curvature of the moon's orbit becomes more than the average curvature of the Earth-moon system, and the moon moves a bit further from the sun, but the moon's orbit never curves away from the sun, nor does it ever 'back up'. The same thing can be said of the Earth itself. In effect, we have a double-planet system.

Calling Luna a planet also meets the quoted definition of a planet, where the gravity overcomes the strength of material (round). Of course, there are a lot of 'moons' of Saturn and Jupiter that are round. In those cases the moons' orbits do curve away from the sun.

Maybe you need to expand your definition and say that it's a bigger than Pluto and is the largest object within a million miles.

[william clark]

Isn't that where the Cyber-Men come from?