Astronomers now claim that Pluto should be a planet

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Long subject. But I wanted to address these two points, among others.

What Philip Metzger (from Univ. of Central Florida) is quibbling about is that he looked at two centuries of research and found just one study, from the early 19th century, that employed the orbit-clearing standard the IAU used to downgrade Pluto. (See https://www.cnn.com/2018/09/10/world/pluto-planet-status-trnd/index.html)

This attitude is no different than the well-known "Peanut Butter argument" used to refute spontaneous generation of life. Namely, if energy, light and heat can spontaneous generate life out of inanimate objects, then you should be able to find life sometimes when you open a jar of peanut butter. Reasonable, right?



The thing is, an object like Pluto that has not cleared its path, is inherently unstable. The last time Pluto was hit by a Kuiper belt object was conjectured to be about one century ago. https://www.skyandtelescope.com/astronomy-news/did-pluto-take-a-punch/.

Sure, we don't see it often. Just like we don't see spontaneous generation of life every time we open a peanut butter jar. But that doesn't mean collision with Kuiper belts doesn't happen. It just happens at a different time scale. That, is the reason why you don't see many scientists talking about "clearing the path" for Pluto, in the last two centuries.

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A picture is worth a thousand words. Here is the situation with Kuiper belt objects and Pluto. (Pluto has the most elliptical orbit in the picture). Pluto's mass is 0.0025 (0.25%) that of the earth. Total mass of Kuiper Belt objects is around 1/25 to 1/10 of the mass of the Earth, or from 4% to 10%. Let's call it 5%, that would be still 20 times larger than the mass of Pluto. In comparison, the mass of Neptune is 17 times the mass of the Earth. What does this tell us? It tells us that (a) Neptune has cleared its path. Kuiper Belt objects and Pluto have insignificant mass as compared to Neptune. (b) Pluto is unstable. Future collisions with Kuiper Belt objects can significantly alter the mass, orbit and the overall identity of Pluto. Now, Pluto takes 248 years to complete a loop on its orbit. So, you probably won't see any collision events for hundreds or thousands of years. But it does happen, as shown above, the last collision could have happened barely one century ago. Unlike the case of Neptune, Pluto's mass is well below the total mass of the Kuiper Belt. Therefore, Pluto is just one member of Kuiper Belt objects. In astronomical time, Pluto's identity (e.g.: mass, orbit, satellites) is unstable.



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The issue of spherical objects near belts is not foreign to astronomers. Saturn's rings offer a good analogy to Kuiper's belt.

How many satellites does the Earth have? If you answer one, then you are short by about 4,000. Yeap, humans have launched about 7,000 satellites, about 2,000 are active today, but about 4,000 of them are floating out there. (There are several estimates out there, here is just one of them: https://www.pixalytics.com/sats-orbiting-the-earth-2018/). Jupiter has 67 moons. Saturn has 62 moons, plus all the objects in its rings.

What's the point? The point is that Pluto have 4 or 5 tiny moons is nothing strange. It's easy to pick up satellites where where Pluto orbits. Kuiper Belt provides plenty of material.

So, the situation of Pluto is not new or unknown. In the case of Saturn, we talk about Saturn's moons, when those moons are far away from Saturn's rings (either at lower or higher orbits). For moon-like objects near Saturn's rings, we don't call them moons: we call them "moonlets." So, borrowing the same idea, Pluto should not be called a planet, but a "dwarf planet."

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The whole point of requiring planets to clear their paths is so that their identities stay stable.

If you say Pluto is stable enough for your liking, then you are resorting to the "peanut butter argument." Two hundred years of human history of astronomy, is barely a blink of eye in astronomical ages.

There is a real issue with the mass of Pluto as compared to the total mass of Kuiper Belt objects. It's the same situation with the moonlets in Saturn's rings. That is at the heart of the debate on whether Pluto is a planet or not. To most astronomers, they would rather view Pluto just as a member of Kuiper Belt objects.

Last edited by eikonabridge on 11 Sep 2018, 2:34 am, edited 1 time in total.

whether or not it is a planet, it SURE WOULD be a neat place to visit!

When the time comes for Plutonian tourism, here's guessing that the travel brochures will advertise trips to the planet Pluto.

and if I was a gazillionaire i'd be first in line.

Actually in 1997 a time traveler from the future by the name of Basil Pike calling into the Art Bell show made a reference to "the planet Pluto".

That was so we turn of the 20/21s century dummies knew that he meant "the heavenly body named 'Pluto'", and not the dog named "Pluto", or the Roman god named "Pluto", or misheard him and thought that he was talking about Popeye's nemesis named "Bluto".

Gravity squashing it to a spherical shape..

I think that everyone can agree to that as part of the definition of a planet. Pluto has that.

Dominating its own part of the solar system (ie dominating solid matter in its orbit) would seem to be part of the definition. But Pluto crosses Neptune's orbit. And doesn't really dominate its part of the solar system.

Some would suggest that size and mass is part of the definition. Trouble with that is that Pluto is smaller than several moons of other planets (including the earths own moon). Promoting our moon to the status of a planet is not out of line in my book. You could view the Earth-moon system as a "binary planet system" (like there are binary star systems)because the Earth's moon is far bigger relative to the size of the Earth than is any other moon in the solar system (with one possible exception: Pluto and its satellite Charon if you count Pluto as a planet).. However if you did that (promote our moon to planet status) you would have to promote like a dozen other moons to planet status. (Triton,Titan, Ganymede, Europa, Io, etc. because of their large size). In fact Titan is almost as wide as planet Mercury, and Ganymede is slightly bigger than Mercury though its less massive than Mercury . That would bump the number of planets up to twenty or more. Too many for grade school kids to memorize.

Can't have that.

either promote Pluto to "plutonian king of the plutonian plutonoids," or back to a planet outright along with its binary partner Charon.

Hear, hear!

I've heard that there is rumors of another planet possibly being somewhere within the Oort Cloud possibly a super-sized earth, but this is hard to define as yet, it's only speculation so, I'll simply say, that Pluto is an astronomical body with great interest in future exploration once we create warp capable technology in the next 1000-1500 years, unless we wipe ourselves out as Carl Sagan had postulated would could occur with many galactic civilizations.

granted, the first direct images from new horizons were eye-openers, but I do so wish they could have zoomed in more to get a better look at its surface features finer than 1 mile resolution. what at maximum zoom look like cracks on the surface may well be zigzag canyons hundreds of feet tall, like a giant maze.

Pluto is definitely a more geologically interesting place than expected.

The moon is geologically dead. Earth is dynamic. And Mars is intermediate. And that seems to correlate with size (moon is the smallest body, Mars is intermediate, and Earth the largest).

But Pluto is smaller than the moon but is more geologically alive than Mars, and second only to Earth. It has tall mountains and Canyons and weird stuff, and even a valentine heart on its shoulder.

However Pluto (a) has been smacked by recent collisions, and (b) is made of "ices" ( methane, ammonia, and water in frozen solid condition), instead of made of rock ( rocks are just objects made of stuff that exists in solid form close to the sun -room temperature- while ices are stuff that liquifies close to the sun but exists in frozen solid form out at the edge of the solar system). So it could be argued that for that reason (composition, and the resulting behavior) Pluto is a different kind of animal than a "planet". Except the trouble with that composition based classification is that then you would then have to subdivide the other "planets" into two very different kinds of animals: terrestrial planets and gas giants.

While I find your post interesting, I’m sure very few people who still want their beloved nine-planet list back, or have adopted an “equidistant” stance, are going to be swayed by being exposed yet again to the same scientific arguments. Most people care a lot more about social things, like honoring the memory of someone born or who worked in their city or state, than about science. If you have to torture the science for those purposes, tortured be it.

A double entendre in one!

I suppose it's all semantics at this point. Maybe we should just call them "Those big ball things what are in the sky or something". Works for me. I like simplification.

Changing from a handy word like "planet" to "T.B.B.T.W.A.I.T.S's" would be a complication, and not a simplification.