How many planets exist in our solar system??

mabsj2 · #1 06-05-2008, 08:19 PM

some years back, i heard that Astronomers world over decided to remove Pluto from the list of planets because of its small size and other un unique features.

but when i read the news and some websites they all talk of 9 planets and others 10.
they claim the 10th is a planet named planet x which i understand is still hypothetical.

so are all these allegations true. are there really 10 planets or there are only 8??

really cofused!!

tbentley · #2 06-05-2008, 10:54 PM

Gotta toe the official line. At least until the line moves......

Ian Robinson · #3 06-05-2008, 11:03 PM

My money is on 10 at least , all depends on how you define an object as a planet.

ngcles · #4 06-05-2008, 11:14 PM

Hi Mabsj2,

Rightly or wrongly and without wanting to court a(nother) long and tedious debate on the merits of the issue, in August 2006 the International Astronomical Union (the international body that governs astronomers) finally and formally defined what constitutes a planet.

The up-shot of that decision is that there are 8 planets orbiting the Sun -- the 6 classical planets plus Uranus and Neptune. The wordng of the definition they came up with, on the face of it, excludes Pluto. For abundant clarity, the IAU passed a _specific clause_ as part of the definition that disincluded Pluto from the Sun's family of planets.

Pluto is now designated a "dwarf planet", as is I believe Eris -- 2003 UB 313 (a Kuiper belt object) and 1Ceres (the largest asteroid).

That is "the law" as it was decreed.

Personally, I don't believe we will find any further major planets orbiting the Sun. It is probable that many, many more Kuiper Belt objects will be found in the next 10-20 years. Some will probably approach or even exceed Pluto in size.

Just because Pluto is no longer designated a major planet, does _not_ mean it isn't (a) interesting or (b) scientifically important, it very much is! It just isn't called a planet anymore.

Best,

Les D
Contributing Editor
AS&T

OneOfOne (Trevor) · #5 07-05-2008, 01:00 PM

I personally agree with the demotion of Pluto, but that is my opinion. So that leaves us with 8. As Les said, I doubt we will find any other objects in the future that will fit the bill for inclusion as a planet as they would be so far away they would be unlikely to be in a "planetary" orbit. As for the number of "Plutinos", I would guess this will grow to be much larger than the number of "planets", perhaps dozens...it is just a pity Pluto won't be the biggest

Mickey would turn in his grave

ngcles · #6 07-05-2008, 03:16 PM

Hi OneofOne & All,

OneofOne wrote:

"it is just a pity Pluto won't be the biggest

Mickey would turn in his grave

"

Turning in his grave!! So when did Mickey die? Has anyone told Minnie the bad news yet?

I suppose in the alternative, Walt might be spinning in his cryogenic chamber!

Best,

Les D

mabsj2 · #7 07-05-2008, 05:35 PM

so there are 8 planets.
not really conviced that there will be any new discoveries. but anything can happen now. got to be ready for anything....

OneOfOne (Trevor) · #8 08-05-2008, 07:41 AM

Quote:

Originally Posted by ngcles

Hi OneofOne & All,

OneofOne wrote:

"it is just a pity Pluto won't be the biggest

Mickey would turn in his grave

"

Turning in his grave!! So when did Mickey die? Has anyone told Minnie the bad news yet?

I suppose in the alternative, Walt might be spinning in his cryogenic chamber!

Best,

Les D

It's just he hasn't made any movies lately...so I thought he must have died! I always thought he was such a great actor...up there with the big names like Fred Flintstone!

Robert_T · #9 09-05-2008, 07:56 AM

interesting that everyone seems to have pretty much accepted the ruling ... personally I think it means very little. really what's a planet is what the majority of people think is a planet. it's all just a subjective construct anyway... i grew up with 9 and see no reason to change, but I'm not dogmatic about it either.

mabsj2 · #10 09-05-2008, 08:22 PM

Quote:

Originally Posted by Robert_T

interesting that everyone seems to have pretty much accepted the ruling ... personally I think it means very little. really what's a planet is what the majority of people think is a planet. it's all just a subjective construct anyway... i grew up with 9 and see no reason to change, but I'm not dogmatic about it either.

cool point there.....

Outbackmanyep · #11 17-05-2008, 08:29 AM

Hi Les and all,
I kind of find it disheartening that they demoted it after Clyde Tombaugh died, but im sure he would have been really pissed if they did it when he was alive!
Poor Clyde!

But the fact remains that Pluto is indeed a dwarf planet, its orbit pretty much gives it away!

If you looked back on history, i bet that a lot of people found it hard to adopt Copernican theory, especially the churches! But in this day and age it may not be so dramatic, but when science changes the goal posts it really is for the benefit of understanding, so Pluto being demoted is a step forward i believe, and i think it has been done in a fair way! Our understanding has grown, so we need to re-define our knowledge to help it grow further.

Cheers!

mabsj2 · #12 18-05-2008, 02:01 AM

Quote:

Originally Posted by Outbackmanyep

Hi Les and all,
I kind of find it disheartening that they demoted it after Clyde Tombaugh died, but im sure he would have been really pissed if they did it when he was alive!
Poor Clyde!

But the fact remains that Pluto is indeed a dwarf planet, its orbit pretty much gives it away!

If you looked back on history, i bet that a lot of people found it hard to adopt Copernican theory, especially the churches! But in this day and age it may not be so dramatic, but when science changes the goal posts it really is for the benefit of understanding, so Pluto being demoted is a step forward i believe, and i think it has been done in a fair way! Our understanding has grown, so we need to re-define our knowledge to help it grow further.

Cheers!

That's true..

proudy · #13 23-05-2008, 01:07 PM

Hi ya Outbackmanyep!

I miss Pluto as a planet, although I knew it was tiny, I didn't realise until recently that Pluto and Charon orbit around a common centre of gravity so which is the planet and which is the moon? This info swayed me to accept Pluto as a dwarf planet.

Some say the solar system consists of the Sun, Jupiter and Saturn and the rest is rubble - seems reasonable!

N

Ian Robinson · #14 23-05-2008, 01:36 PM

Titan has an atmosphere , and it's big too (> 5100km diam and is bigger than Mercury) , so although it orbits Saturn , I think it should be classed as a captured planet.

The larger Jovian moons maybe too (especially the ones with atmospheres and oceans).

It would likely be called a planet if it was in it's own orbit about the sun.

renormalised (Carl) · #15 04-06-2008, 11:28 AM

If you ask the guys on Jupiter (if there were to be peeps there), they would consider Earth as being nothing more than a bit of flotsom... "You call THAT a planet??!!!". Laughter would ring through the room

Boton · #16 06-06-2008, 10:57 PM

It is very serious when can't even come to a conclusion of what is a planet?

But it doesn't matter, they will change their minds again as something new is just around the corner, and this "new" information will help a lot to better understand blah blah blah.

How many planets then?
Based on what/who?

The older I get, more confused I become

Thank you if you can bring some light into this subject.

mojo (Terry) · #17 06-06-2008, 11:13 PM

Strange to call a planet a dwarf planet and consider it not to be a planet.

astroron (Ron) · #18 06-06-2008, 11:35 PM

Personally, I don't believe we will find any further major planets orbiting the Sun. It is probable that many, many more Kuiper Belt objects will be found in the next 10-20 years. Some will probably approach or even exceed Pluto in size.
As quoted from Les D
He is probably on a good wicket

But I have a bet with a very knowledgeable friend that we will find a companion to the Sun in the very near future

I am not alone

http://www.binaryresearchinstitute.org/index.shtml
Ron

astroron (Ron) · #19 06-06-2008, 11:39 PM

Quote:

Originally Posted by mojo

Strange to call a planet a dwarf planet and consider it not to be a planet.

To True Terry,

but it is not a Classical Planet

Everything must be put in it's place

We must have order

Ron

cahullian · #20 07-06-2008, 05:38 PM

I voted 8 planets. Pluto is too small to be classed as a planet. It doesn't matter what we class it as, it still has the same job to do today as it did at the formation of the Solar System. In a Billion years time long after Mankind has had it's day in the sun and we are gone the way of the Dodo. The next intelegent species (ones that are smart enough not to turn a beautiful blue planet into another Venus) may call it a planet again : )

Gazz