Gee, where did the time go? Those 2 years just flew by.
But be that as it may, (and I doubt if it ever was) …
I think Pluto should be reclassified as a genuine planet. (The New Mexico legislature has designated it with planetary status in honor of Clyde Tombaugh, Pluto’s discoverer and a longtime New Mexico resident).
My “planetary” defintion is
• the lower limit of planetary radius is 1,000 kilometers (Pluto is 1,195 kilometers) and
• maximum average orbital distance from the Sun as 40 astronomicl units.
(Pluto’s is 39.5)
Okay, I’ll admit that is sort of “forcing” Pluto to belong with the other other 8 planets.
However, it does get rid of those “problems” such as Ceres (close enough but not big enough) and Eris (big enough but not close enough).
So, we still have 9 planets just as before.
(Okay, this posting wasn’t written with 100% seriousness, but don’t you think Pluto needs to have its planetary status reclaimed?)
Sorry to disagree with you, wolf_meister, but I think the change was spot-on.
I can see how your definition would work - but it’s also obviously being backed in to deliver a specific result - i.e. restore Pluto to planetary status, while still excluding the other Kupier belt objects that have been discovered, or will be discovered.
IMNSHO, Pluto only was granted planetary status at first because it’s mass was grossly over-estimated based on someone’s mistaken pencil and paper calculations of observed variations in Neptune’s orbit. Now that we know the mass of Pluto, and know that the Kupier belt objects exist, I think it makes a lot more sense to stick with the minor planet definition that was hammered out two years ago.
My two cents and worth only about half what you paid for it.
Although I guess I’ve come to terms with Pluto being demoted, if we’re going to make it a planet again, rather than contriving some set of rules whereby Pluto gets to be a planet but Ceres doesn’t, make Ceres a planet too. (What the heck, it used to be a planet.)
One concern I saw expressed at the time about the idea of designating Pluto, Eris, et al. as full planets is that we’d wind up with dozens and dozens of planets (Mercurcy, Venus, Earth, Mars, Ceres, Pallas, Vesta, Jupiter, Saturn, Uranus, Neptune, Pluto, Eris, Makemake, Quaoar, Sedna, Orcus, Ixion, Varuna…)
To which I say, bring 'em on! I think it would be shiny to live in a Solar System with 40 or 50 planets.
Personally I would have been fine with more planets. To me, objects with a strong enough gravitational pull to spherify themselves are either planets or moons.
I’ll admit I was trying to force the issue in Pluto’s favor.
Still, I think my idea of distance may have some merit. If an object were discovered that had a one light year oribtal radius about the Sun, (if I remember my Kepler’s Law correctly), it would take a “mere” 15,900,000 years to orbit the Sun. For one thing, could we be sure that everything in its nearly 16,000,000 year trip, was swept out of the way? If so, can we be sure that something will never wander into what was once a clear path and thereby revoking that object’s planetary status?
I know that a planetary object at that huge distance has an almost zero chance of ever being discovered, but doesn’t it seem a bit strange to think of something with an orbital period of almost 16,000,000 years to be part of the Solar System?
I like MEBruckner’s and Sage Rat’s redefining of planetary status. Of course the mnemonic for remembering the order would be very difficult and no doubt subject to constant revision.
Well, we need a challenge. Heck, I memorized the names of the planets in their order from the Sun when I was a wee lad, and I’d probably have to remember any mnemonic for them backwards: “Mary Very Earnestly Made…let’s see, ‘J’ for Jupiter, so it was something that starts with ‘J’…”
Eris, Makemake, Quaoar, Sedna, Orcus, Ixion, and Varuna, on the other hand, still sound exotic. (Well, except for “Makemake”. I keep wanting to stick an adjective in front of that one. “Grilled” or “blackened” or maybe “lemon pepper”.) (15760) 1992 QB1 also needs some work, but even it has a certain charm: “Captain’s Log, Stardate 3.14159: We’ve been dispatched to Planet QB1 to investigate possible deposits of plotdrivium ore…”
I don’t have a big problem with Pluto not being a planet (it’s not what we thought it was when it got named as such), but this ‘dwarf planet’ business is just dumb, and the IAU vote on it was highly irregular, to put it kindly.
That said, I’m with those that would let nearly anything round enough to be called a planet, and just do away with this notion that there’s a set number of them. Kids can get excited about dinosaurs without having to memorize every single species ever found.
Someone smart should just come up with an “H-R diagram for stuff that’s smaller than stars.”
Star: a celestial object that puts out more energy than it receives because of nuclear reactions.
Planet: a celestial object that pulls itself into a sphere because of gravitational self-attraction, but does not generate more energy than it receives. (This excludes both stars and objects that are not spherical or that self-spherify because of, say surface tension.)
Moon: an object in orbit around a planet. Moons can be artificial, planets, non-planets, even stars (not sure if that’s possible with a really big planet and a really small star).
The issue I have with the whole “clearing the orbit” part of the current planet definition is, how do you tell for remote objects? Why leave some objects in limbo because you can’t see parts of their orbits? To me, an object’s planeticity ought to be judgeable no matter where it is. And none of this “it’s only a planet if it’s in our solar system” either.
So this leads to a solar system with 157 “planets”, many of which are also moons. We’ll just have to deal with it.
Precisely. Using my example of an extremely remote planet, one light year from the Sun and taking 15,900,000 years for each orbit, could we really tell if it has swept out everything in its path and would it remain completely swept out forever?
Let’s suppose a 10,000 km diameter object is detected at 75 astronomical units. The size certainly would qualify it for planetary status but would we really be able to determine just how clear that orbital path would be? I agree that the “clearing the orbit” condition for planethood is very unclear and subjective. The International Astronomical Union should seriously reconsider redefining its definition of “planet”.
Me, too. I remember being taught by my 3rd grade teacher: “Mercury, Venus, the Earth, & Mars…these are the planets that dwell near a star. Jupiter, Saturn, Uranus, too, Neptune, & Pluto, I know them…do you?”
Jupiter hasn’t either - there are clusters of asteroids sitting in some of the Lagrange points of Jupiter’s orbit. I believe these are called Trojan asteroids. Somehow that doesn’t disallow big Jove as a planet.
