Horizon 9pm Tonight

[Weather-history]

Horizon's program tonight is about whether Pluto will lose its planet status

http://news.bbc.co.uk/1/hi/sci/tech/5099292.stm

I wrote to Patrick Moore about this a few years back and he said he doesn't believe Pluto is a planet but one of the larger members of the Kuiper belt.

[shuggee]

What a fascinating read. The boys and girls on the Programme 'QI' will have a field day with all that information and speculation of definitions. Did you know there is more than one moon of earth for instance?!

[agowerguy83]

I think Pluto should continue to be classed as a planet for historic reasons, but there should be a minimum requirement for any planetary objects found since Pluto, like recent objects, Sedna and "Xena".

[Dazza]

An interesting read, what a blow to history that would be!

[Weather-history]

I think Pluto should continue to be classed as a planet for historic reasons, but there should be a minimum requirement for any planetary objects found since Pluto, like recent objects, Sedna and "Xena".

Ganymede is the largest natural sattelite in the solar system, it has a diameter of about 5300 kms and is larger than Mercury and Pluto

Titan has a diameter of 5150kms and is also larger than Mercury and Pluto and even has its own dense atmosphere and yet its not even classed as a planet.

This is where the trouble really arises

[Angel15]

Ganymede is the largest natural sattelite in the solar system, it has a diameter of about 5300 kms and is larger than Mercury and Pluto

Titan has a diameter of 5150kms and is also larger than Mercury and Pluto and even has its own dense atmosphere and yet its not even classed as a planet.

This is where the trouble really arises

Do you think it possible, Mr Data, that there is micro-organism type life forms on any other planet?

[kold weather]

This is gonig to be very intresting and it'll be intresting to see the outcome of it as well. The problem is if you class Pluto as a Planet, then you've also got to class several large Aseroids and also several moons.

As Mr.Data said Ganymede and Titan both would be prime contenders to be upgraded to planetry status, considering that not that much smaller then Mars. Even our moon would probably have a fair shout because of its large size, because its bigger then Pluto by over 1000km.

[Weather-history]

This is gonig to be very intresting and it'll be intresting to see the outcome of it as well. The problem is if you class Pluto as a Planet, then you've also got to class several large Aseroids and also several moons.

As Mr.Data said Ganymede and Titan both would be prime contenders to be upgraded to planetry status, considering that not that much smaller then Mars. Even our moon would probably have a fair shout because of its large size, because its bigger then Pluto by over 1000km.

Put it this way, I find it hard to put Titan and Phobos under the category of "moons" when Titan is larger than Pluto and Mercury whilst Phobos is a mere 22km in diameter.

There is another problem, I call them "joke moons" like Phobos. In reality, Phobos and Deimos are captured asteroids.

[stella]

I bet they don't mention the words "Nix" 0r "Hydra".

[SnowBear]

I think the rule "is the object spherical", ie does it form a spherical shape under its own gravity, is an important point. And also does it have its own unique orbit around the sun.

So, if its spherical, with its own orbit around the sun, would be a planet, regardless of size or distance from the sun, and a moon would be a spherical object orbiting a planet, again, regardless of size or distance.

Sounds like they are trying to make it too complicated in some ways.

[summer blizzard]

Personally, i think that one of the criteria should be, does the planet have an atmosphere, while i do not think any of Jupitors moons should be classed as planets, i think that Titan should be classed as the twin planet of Saturn.

[Angel15]

Personally, i think that one of the criteria should be, does the planet have an atmosphere, while i do not think any of Jupitors moons should be classed as planets, i think that Titan should be classed as the twin planet of Saturn.

I think that is a good criteria - and a sensible one

[Methuselah]

But, where does the 'atmosphere' criterion leave Mercury?? And what will Venus, Earth and Mars become, when Solar expansion drives-off their atmospheres??

Not that there'll be anyone around by then...

[Cloudburst]

tbh i think pluto should be classed as a planet for its asthetic properties but scienfically it is not a planet, just a case of luck really

[stella]

Yeah I saw that show, too. Good stuff, really.

It's not true, Cruithne and other corkscrew asteroids are not moons of the Earth, even though it does have major effects on the orbits round the Sun that these objects follow.

[Bottesford]

Personally, i think that one of the criteria should be, does the planet have an atmosphere, while i do not think any of Jupitors moons should be classed as planets, i think that Titan should be classed as the twin planet of Saturn.

So Mercury is no longer a planet then! Pluto would actually *just* count as one as it has a very thin atmosphere.

Titan-Saturn a twin planet?! Saturn must be many thousands of times larger so hardly a double planet. Pluto & Charon could be classified as a double planet as Charon is half the size of Pluto (and so there centre of gravity is actually above Pluto's surface- I think)

I say keep Pluto a planet and let anything else larger than it found in the Kuiper belt to be planets too. Fairly vague from a scientific stance but would make sense to most.

Annoyingly I missed Horizon tonight only remembering at ten past ten! Luckily I think my brother has recorded it to his PC.

As to the person mentioning if there's any life on other planets- I think we will find some eventually. It's likely to be simple organisms with likely candidates being Mars, Europa, Enceladus or possibly Titan.

[Scribbler]

We still refer to many things that earlier generations ‘discovered’ that don't really exist, such as the Seas of the Moon and the canals of Mars. Surely therefore, Pluto, regardless of its real status, must be preserved as a planet.

Perhaps we should retitle our basic nine planet solar system as something like “Ancient Planets” and use “Modern Planets” for the newer and recently added members of our system.

Leave Pluto as an “Ancient Planet” and include all the Kuiper Belt objects etc, as “Modern Planets”.

[Weather-history]

Perhaps we should retitle our basic nine planet solar system as something like “Ancient Planets” and use “Modern Planets” for the newer and recently added members of our system.

Leave Pluto as an “Ancient Planet” and include all the Kuiper Belt objects etc, as “Modern Planets”.

One problem

The planets: Mercury to Saturn were known to the ancients. they could be described as ancient planets

Uranus, Neptune and Pluto are "modern" planets, Pluto was discovered in 1930.

Calling Pluto, an "ancient" planet is a misnomer because its existence has only been known in the last 76 years.

[agowerguy83]

A planet to me, is a fairly round object that orbits the sun directly (not orbiting another planet which is orbiting a star, unless its a double planet), and a certain size, I would include Pluto and 2003 HB313?

As it said in the programme last night if the new definition of a planet excludes Pluto some may well ignore the revised definition.

Maybe we should have the Inner Planets, the Gas Giants and the Keiper Belt Planets

[shuggee]

It's not true, Cruithne and other corkscrew asteroids are not moons of the Earth, even though it does have major effects on the orbits round the Sun that these objects follow.

There are at least three natural satellites other than the moon which orbit earth - not the sun. Am I right in saying any body which orbits a planet is a satellite of that planet?

[Weather-history]

I have a problem with some of the so called "moons"

Take Phobos, 22km in diameter that is a "moon" of Mars. If you put Phobos into orbit around the Sun, what would it be classified as? An asteroid

Take Titan, 5150km in diameter and send that into orbit around the Sun, what would it be classified as? A planet

Thats a bit of a difference.

The reality is Phobos and indeed Deimos, the other "moon" of Mars are in reality captured asteroids.

[Scribbler]

One problem

The planets: Mercury to Saturn were known to the ancients. they could be described as ancient planets

Uranus, Neptune and Pluto are "modern" planets, Pluto was discovered in 1930.

Calling Pluto, an "ancient" planet is a misnomer because its existence has only been known in the last 76 years.

I just knew that you'd pick up on the word 'ancient'!

What I'm trying to imply is that at some point we could define existing named/known/approved planets as 'ancient' (forget the Greek/Roman use of the word 'ancient') and objects found since up-to-date (computerised?) searches were used as 'Modern'.

Just trying to help!

[Angel15]

I think it should be left as it is now - with respect, I think it is a lot of hoo har.

[Somerset Squall]

I think it should be left as it is now - with respect, I think it is a lot of hoo har.

Yes, it has been regarded as a planet for so long now, I think it should be left has having "planet" status for historical reasons.

[Summer of 95]

Mercury has no atmosphere (IIRC) and is still classed as a planet. I will always think of Pluto as a planet because it's what I've been brought up thinking, although I see the scientist's points of view (especially WRT its orbit, for 20 years it wasn't the outermost of the nine).

Regarding moons, there are loads of these "captured asteroids", many of the smaller moons of Jupiter and Saturn for instance. There's also a theory that Neptune's moon Triton is a captured Kuiper Belt object.