BS: How many planets are there?

Subject: BS: How many planets are there?
From: Paul Burke
Date: 16 Aug 06 - 10:48 AM

Astronomers are thinking of redefining planets, as a result of newly discovered objects in the solar system. They reckon that this will increase the number of planets to 12, will Ceres, Charon and the new UB313 (Xena) being added.

But by their own criteria, they should also include the Moon. It's round, and it orbits a star. No, I hear you cry, it orbits the Earth. But the Earth orbits the Sun, and look at it as though you were in a spaceship above the Earth/Moon orbit.

The Moon's orbit round the Earth NEVER goes backwards relative to the Earth's orbit round the Sun. The average orbital speed of the Earth is about 1.6 million miles a day. The Moon's average orbital speed around the Earth is about 55 thousand miles a day- so even when orbiting "backwards" relative to Earth it has only reduced in Sun orbital speed by about 3.5%.

So from your spaceship, the two planets seem to be going at roughly the same speed together, with the Moon wiggling along an orbit that takes it sometimes ahead of the Earth, sometimes behind, sometimes inside its orbit and sometimes outside. It's a twin planet system. What's more, the Moon is larger than Pluto.

So fair's fair; if astronomers want to keep Pluto, they've got to promote the Moon.

Subject: RE: BS: How many planets are there?
From: Paco Rabanne
Date: 16 Aug 06 - 11:05 AM

No. The moon orbits the Earth, pluto orbits the sun hence it's a planet.

Subject: RE: BS: How many planets are there?
From: Ebbie
Date: 16 Aug 06 - 11:05 AM

But Pluto's standing is controversial too, right?

Subject: RE: BS: How many planets are there?
From: MMario
Date: 16 Aug 06 - 11:08 AM

well - the are basically redifening "planet" - and then making different classifications of "planets".

Subject: RE: BS: How many planets are there?
From: Bunnahabhain
Date: 16 Aug 06 - 11:17 AM

Well, we know of several hundered planets, almost all of them larger than Earth. Most of them just happen to obit other stars...

Subject: RE: BS: How many planets are there?
From: DMcG
Date: 16 Aug 06 - 11:39 AM

Although 'retired' is right, it is not as clear as you might think, since Charon was previously regarded as a moon of pluto, and looks likely to become a new planet (or more accurately a pluton). So the distinction between "moons" and "planets" is not always straightforward.

Subject: RE: BS: How many planets are there?
From: DMcG
Date: 16 Aug 06 - 11:42 AM

It's just struck me - what, if any, impact does this have for astrologers?

(Short answers only, please!)

Subject: RE: BS: How many planets are there?
From: Paul Burke
Date: 16 Aug 06 - 11:44 AM

Bunnahabhain , Solar system we're talking about here. Daresay there are 10 to the 64 planets out there beyond.

retired: the moon orbits the sun too. That's what I was pointing out.

Subject: RE: BS: How many planets are there?
From: Paul Burke
Date: 16 Aug 06 - 11:47 AM

Since astrologers haven't even updated their star signs to include Neptune and Pluto, and haven't corrected for the precession of the equinoxes, I don't think they'll care too much. Maybe adding the new objects will improve their predictions.

Subject: RE: BS: How many planets are there?
From: Stilly River Sage
Date: 16 Aug 06 - 11:50 AM

They did a very nice discussion of the planet designation question on National Public Radio's Morning Edition today. The Hayden Planetarium doens't list Pluto as a moon, for example, but he said there are probably over 40 bodies of some sort or other that should be elevated to planet status if Pluto is to be considered a planet in scientific circles.

Think of all of those obsolete solar system models. :)

SRS

Subject: RE: BS: How many planets are there?
From: Hand-Pulled Boy
Date: 16 Aug 06 - 11:55 AM

With no moon I'm going to have to re-write my bestist song!

Subject: RE: BS: How many planets are there?
From: harpmolly
Date: 16 Aug 06 - 12:00 PM

Whoa, this is going to knock mnemonics on its ass. ;)

"My Very Educated Mother Just Served Us Napoleons"?

OR (should the decision swing the other way)

My Very Educated Mother Just Served Us Nine Plump, Crispy, Chewy X...(I got nothin'!)

Molly

(P.S. Sorry guys, I've gotta come down on the side of the Moon orbiting the Earth. Technically, yes, it also orbits the Sun (in a "mouse in your pocket" kind of way), but its primary orbit is around the Earth. If we're going to add any significant planetary moons as planets in their own right, I think the list is going to get pretty darned long. ;))

Subject: RE: BS: How many planets are there?
From: DMcG
Date: 16 Aug 06 - 12:05 PM

Your mnemonic had Ceres in the wrong place, I think. It needs to be

My Very Educated Mother, Clara, Just Served us Nine Chicken Pies. X.

(That business with Pluto and Charon swapping places is going to be a real trouble-maker)

Subject: RE: BS: How many planets are there?
From: DMcG
Date: 16 Aug 06 - 12:08 PM

Lets make it Celia rather than Clara, then we have 'Ce' and 'Ch' to remind us which is which! (and notice that 'MY' matches MercurY and MotheR matches MaRs)

Subject: RE: BS: How many planets are there?
From: Bill D
Date: 16 Aug 06 - 12:43 PM

The astronomers were having a nice, learned discussion on what to do about nomenclature...then they let slip to the public that they were considering downgrading Pluto....Oh, HORRORS! Outcries from kids & Disney fans poured in.."Pluto is my FAVORITE..don't mess with its status!"

A lot of the recent debate is actually centered on just how to define astronomical bodies 'out there', and not upset 'fans'. arrrgghhh! (They 'may' go to listing the whole class of roughly spherical bodies outside Neptune's orbit as "Plutonoids", just to give it a 'feel'. I'm sure Mickey & Minnie will be pleased.

Subject: RE: BS: How many planets are there?
From: Nigel Parsons
Date: 16 Aug 06 - 12:49 PM

Before we get too deeply into the mnemonics for the relative positions counting from the Sun, remember these mnemonics were wrong for a large part of the lives of many of us. If you're under 40, Pluto has been nearer the Sun than Neptune has for over half your lifetime!
At times Pluto is closer to the Sun than Neptune (as it was from January 1979 thru February 11 1999).

Just to throw in some dissent
CHEERS
Nigel

(reference from Pluto)


Pluto picture

Subject: RE: BS: How many planets are there?
From: Les from Hull
Date: 16 Aug 06 - 01:05 PM

What about Mongo?

Subject: RE: BS: How many planets are there?
From: Paul Burke
Date: 17 Aug 06 - 03:51 AM

And Colin Matthews has only just added Pluto to Holst's Planets.

Subject: RE: BS: How many planets are there?
From: A Wandering Minstrel
Date: 17 Aug 06 - 08:17 AM

Here's a reasoned argument:

Fool: The reason why there are 7 stars is a very pretty reason.
King Lear: Because there are not 8?
Fool: Truly, thou wouldst make a good fool!

Subject: RE: BS: How many planets are there?
From: Alba
Date: 17 Aug 06 - 08:35 AM

Well I think it is very nice that they have named one of the new Planets after the famous Warrior Princess, Xena.
Jude:)

Subject: RE: BS: How many planets are there?
From: MMario
Date: 17 Aug 06 - 08:39 AM

whatever happenned to Sedna?

Subject: RE: BS: How many planets are there?
From: Alba
Date: 17 Aug 06 - 09:13 AM

I thought I had read or heard that Sedna is not officially classified as a planet MMario:(

Subject: RE: BS: How many planets are there?
From: Scoville
Date: 17 Aug 06 - 10:18 AM

Saw a bit on the news last night that made the argument that it doesn't really matter how many planets there currently are as long as kids learn how it's all researched. (Which will never be taught, but I can dream, can't I?)

Subject: RE: BS: How many planets are there?
From: Clinton Hammond
Date: 17 Aug 06 - 11:55 AM

"what, if any, impact does this have for astrologers?"

It's not like astrology could get any more useless.....

Subject: RE: BS: How many planets are there?
From: Wolfgang
Date: 17 Aug 06 - 12:20 PM

But by their own criteria, they should also include the Moon (Paul Burke)

Wrong. By their own (not yet adopted) criteria, the Moon remains a moon and Charon would be upgraded to a planet. Why? The position of the common center of gravity of a "planet" and a "moon" defines according to the new criteria whether the "moon" is a moon or is upgraded to a planet sharing roughly the same orbit with the original "planet". When the common center of gravity (around which both orbit) is within the larger of the two bodies then the smaller one is a moon, if the common center of gravity is some place between the two bodies orbiting a star then both are planets.

One may call that definition arbitrary but the classification of the Moon as a moon is consistent with the new criteria.

Wolfgang

Subject: RE: BS: How many planets are there?
From: JohnInKansas
Date: 17 Aug 06 - 02:40 PM

The article in my local rag indicated that one fellow who was a leader in insisting that a new and more consistent definition is needed now says he doesn't like what they've come up with.

His objection may have something to do with the need for him to now prepare all the statistics and submit the new objects he's reported discovering, and he say's he has "about 53 of them" that will have to be cussed, discussed, and debated to decide whether each of them should be called a planet under the new definitions.

If he doesn't get a bunch of grad students (a euphemism for slave laborers) to help, the paperwork is definitely gonna cut into his coffee breaks.

John

Subject: RE: BS: How many planets are there?
From: MMario
Date: 17 Aug 06 - 02:58 PM

That there are a number of moonlike objects (nix and hydra) ALSO orbiting the center of gravity of the Pluto/Charon pair lends credence to declaring Charon a planet and the pair the first official binary planet pair. Since the center of gravity is NOT within Pluto or Charon it is hard to describe the moonds as "orbiting" either - but they CAN be decribed as orbiting the PAIR of planets.

Subject: RE: BS: How many planets are there?
From: catspaw49
Date: 17 Aug 06 - 02:58 PM

Rethinking astronomical bodies? Okay, I'll just sit here and think about Charlize Theron.

As far as the planets go, and just on a real personal basis, I couldn't possibly give a shit less. That's just me of course......Y'all are free to go on with this stimulating and invigorating conversation. I am all atwitter over what will happen next!

Spaw

Subject: RE: BS: How many planets are there?
From: Raedwulf
Date: 17 Aug 06 - 03:06 PM

Wolfgang has put hammer & nail together quite accurately.

On the subject of Sedna, Quaoar, & various others, at the moment they are all "pending further investigation". To quote, "More objects are likely to be announced as planets in the future. The IAU has a "watchlist" of at least a dozen other potential candidates that could become planets once more is known about their sizes and orbits.

These include the distant objects Sedna, Orcus, Quaoar and 2003 EL61 and the asteroids Vesta, Pallas and Hygiea."

Full BBC story here

Subject: RE: BS: How many planets are there?
From: Don Firth
Date: 17 Aug 06 - 03:14 PM

Good, Wolfgang. That's my understanding also.

Don Firth