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Should Pluto be a Planet or be a Dwarf Planet


DommyDevil18
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Which reminds me, my history is poor, help me out here - at the time of Pluto discovery was it not recognised that it was not sufficient to be the cause of the pertubations? Did they (he) continue the search ? Were those pertubations real or mathematical quirks/mistakes ?

If they were real have they been accounted for since or is Planet 10* still out there ?

IIRC when it was discovered it was noted to be dimmer than expected, suggesting that it was either smaller or very dark. Size estimates were progressively revised downwards, and it became realised that it wasn't the Planet X people were looking for.

The perturbations have now been accounted for by a more accurate measurement of the mass of Neptune, found by the Voyager mission.

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One thing I meant to add, I don't think there is anything wrong with describing Pluto as a planet in casual usage. It's a planet, sub-category dwarf in much the same way that Jupiter is a gas giant and the Earth a rocky planet.

The current IAU definition has I feel a critical flaw. A body more massive than Mercury, even more massive than the Earth, would be called a "dwarf planet" if it orbited far enough from its star. That is I feel an absurdity.

As long as such a body remains hypothetical, the IAU definition can be got away with. But sooner or later we'll find a real Super-Mercury or Super-Earth dwarf planet orbiting another star, and then I think our definitions will warrant revision.

Simply defining a "planet" as being something orbiting a star, large enough to be gravitationally rounded, and not large enough to fuse deuterium does mean that our solar system has not eight or nine planets, but probably close to a hundred. However, I don't see that as a problem. It's a considerable change in our understanding, but that's happened before; we used to call the Sun and Moon planets and the Earth not one. With the more inclusive defintion of "planet" we would recognise that most planets are pretty small Ceres or Pluto-like objects, and that large terrestrials and gas giants though easy to spot are rare.

Indeed, if we must draw a distinction, then absent any prior prejudices it would not be between planets and dwarf planets, but between gas giants and solid planets. Earth and Mars are a lot more like Ceres than they are like Jupiter. (Realistically though we're not going to make either Earth or Jupiter not a "planet" of course.)

I don't quite agree, but you do make some good points. Looking at it another way, on average dwarf planets are much smaller and less massive than planets, even if there is some potential for overlap. It's not ideal but it's more a problem with the term 'dwarf', rather than the classification scheme itself. Perhaps 'planetoid' would have been better, but it's a bit late now.

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I still feel it has a colourful and chequered past when it had 6 Planets then 11 back to 6 then 7 then 8 then 9 now back to 8 if it had more we would be asking ourselves so what is a Planet and what is not a Planet. But imagine that Mercury Venus Earth Mars Ceres Jupiter Saturn Uranus Neptune Pluto Eris Haumea Sedna and Makemake that will be 14. I would feel like that Astronomers are very undecisive.

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Percival Lowell has a lot to answer for.  About a hundred years ago he had much, if not most, of the educated world believing that martians were building irrigation canals on Mars. He argued that they were republicans because only republicans could organize global projects on that scale. He also argued that there was a Planet X. There was no more a planet X than there were republican canal builders on Mars. It was all drivel, quite honestly. A rock was discovered in orbit about where the imaginary planet X was supposed to be. Thinking it was planet X we called it a planet and called it Pluto. Enough is enough. Lowell needs to take a rest.

The great E E Barnard would have none of his canals and we shoulld have none of his Planet X, say I, but does money have to talk? Lowell had money. Pluto isn't planet X. It's a rock.

Olly

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It makes sense IMHO for it to be excluded, though I may not gain any popularity for saying so,  but there is no point attaching sentimental historical values to something for the sake of what is in the best interest for science. If the reclassification had not been made, there would be a bigger grey area of other bodies that could arguably also qualify as a planet.

One of my thoughts exactly :) Imagine if like I already said the Solar System had Mercury Venus Earth Mars Ceres Jupiter Saturn Uranus Neptune and Pluto all as Planets what would that make other round objects orbiting the Sun. Would that make the Moon a Planet also? If it were then their would be 184 Planets in the Solar System if all the moons became planets as well added with the three more forgotten in Pallas Juno and Vesta overall 187 Planets imagine trying to remember that. Please correct my maths if I am wrong but that is not a bad attempt for someone with minute dyslexia.

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I've found a definitive answer. Pluto is not a planet. My source - the box of glow in the dark planets I got from the Glasgow Science Museum for a make your own solar system kit (suitable three year old and above). Now don't tell me there is a more definitive source than that!

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I've found a definitive answer. Pluto is not a planet. My source - the box of glow in the dark planets I got from the Glasgow Science Museum for a make your own solar system kit (suitable three year old and above). Now don't tell me there is a more definitive source than that!

Ah, go on, make your own Pluto and stick it in there, I dare you :grin:  :grin:

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It honestly bothers me not a jot.  It's just a label.  What we call Pluto changes nothing of its nature, its physics nor its interest.  Names and labels say more about the people who use them than the things they're applied to.  So call it what you like.  I still can't find the damn thing in a telescope :)

James

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I've found a definitive answer. Pluto is not a planet. My source - the box of glow in the dark planets I got from the Glasgow Science Museum for a make your own solar system kit (suitable three year old and above). Now don't tell me there is a more definitive source than that!

Somewhere out there is a warehouse filled to the brim with glow-in-the-dark pluto models.

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It makes sense IMHO for it to be excluded, though I may not gain any popularity for saying so,  but there is no point attaching sentimental historical values to something for the sake of what is in the best interest for science. If the reclassification had not been made, there would be a bigger grey area of other bodies that could arguably also qualify as a planet.

I was the same I was not the most popular for having this belief. 

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