Slashdot Mirror
2 Planets Can Share the Same Orbit, In 3 Different Ways
StartsWithABang writes: One of the most important characteristics of a planet, at least according to the IAU definition, is that it clear its orbit of all other bodies. But if we allowed for a special caveat — the possibility of two similarly-sized objects sharing the same orbit — could we have a stable configuration where that occurred? Surprisingly, not only is the answer yes, but there are three ways to do it: to have one at the L4/L5 Lagrange point of the other, to have a close-orbiting binary planet, or to have orbit-swapping worlds, where they periodically change spots with one another. Unbelievably, our Solar System has a history of all three!
One Orbit
Given that the third mass needs to be negligible for the Lagrange points to work (at least according to Wikipedia), to me it seems like this situation might be more like a strange type moon rather than a planet. What is or isn't a "planet" is just a random definition so there isn't really a right answer.
GENERATION 27: The first time you see this, copy it into your sig on any forum and add 1 to the generation.
How many different ways are there to rehash shit that everybody knew since forever into crappy clickbait articles?
Confucius say, "Find worm in apple - bad. Find half a worm - worse."
Stack overflow.
Slashdot, fix the reply notifications... You won't get away with it...
This. Seriously, I'm getting sick of having Ethan's blog everywhere I go. Guy's good at manipulating social media, but there's nothing on any of his post that isn't just a rehash of things that Slashdot and other tech/science blogs have already linked to years ago.
One of the most important characteristics of a planet...
There's three characteristics, and this is probably the least important. But if you consider all three to be "the most" important, then I suppose it's one of them. That seems like a pretty silly way to express yourself, though. Personally, I'd probably just say "one characteristic".
Also note that we're talking about the IAU definition, which is not necessarily the only definition. Dictionaries still haven't accepted the IAU definition, and may never do so, because the IAU defines a planet as orbiting the sun, while science fiction writers continue merrily talking about planets around other stars, and show no signs of changing.
... please at least check whether the links in the submission are going anywhere...
And don't forget that Pluto crosses Neptunes orbit as well.
Can we please have warnings on links to Forbes? Those interruptions for their (usually stupid) "thought of the day" are really annoying. Perhaps editors should look for alternative sources where possible.
const int one = 65536; (Silvermoon, Texture.cs)
SJW, n: "Someone I don't like, and by the way I'm a fuckwit" - AC
They'll say, "oh, it's okay, there's enough of a size difference between those bodies that they don't count". But the thing is that there's no way that most of the current "8 planets" would have cleared their orbits without help from the giants. It's pretty much accepted science in astronomy that Jupiter, and to a lesser extent Saturn, scattered most of the bodies in our solar system. Mars has a Stern-Levison parameter (rating of the ability of a body to scatter small bodies) two orders of magnitude less than Neptune, and Neptune has multiple Pluto-scale bodies in its orbit. Pluto may be small compared to Neptune, but it's not so small in comparison to Mars, yet Mars has two orders magnitude less ability to scatter them. Mars didn't scatter these things away - Jupiter did. Heck, a number of the models show that the planets didn't even form in their current locations.
There's all this misuse of the Stern-Levison parameter out there to say things that it doesn't. The parameter is based around a probabilistic simulation of the body and a bunch of "small bodies" with a mass distribution and orbital distribution similar to our asteroid belt. But of course, that tells you very little - our asteroid belt only has the size and mass distribution that it does today because of the influence of other planets - and when I say "other planets", I really mean overwhelmingly Jupiter (only a tiny fraction of asteroids are in Mars resonances). Jupiter has stopped these bodies from coalescing into larger bodies and scattered the vast majority of its mass elsewhere. That's not the situation that the solar system was in during formation. There were numerous large "planetissimals" scattered around. The Stern-Levison parameter says absolutely nothing about the ability of a body to scatter large planetissimals. And even concerning scattering asteroids, it doesn't state that the scatters are enough to "clear the orbit", only that their angle changes on a pass by more than a given number of degrees.
Basic point: a standard based around the "8 planets" having cleared their orbit is a lie. The science says that most of them aren't responsible for clearing their own orbits.
And while we're at it: what sort of stupid standard puts Mars and Jupiter in the same group but in a different group than Pluto and Ceres? There was a perfectly reasonable standard under discussion at the IAU conference shortly before they switched what they were voting on: a definition built around hydrostatic equlibrium. A lot of the planetary scientists left thinking that this was the version that was going to be voted on, and being happy with either "no definition" or an "equilibrium definition", saw no need to stick around for the final vote. Hydrostatic equilibrium actually is valid science, and it's very meaningful. A body not in hydrostatic equilibrium is generally made of primordial minerals. It's the sort of place you'd go to research, for example, properties of how the solar system formed. A body in hydrostatic equilibrium has undergone mass conversion of its primordial minerals to new forms. It's undergone massive releases of energy (which may still be present, depending), associated action of fluids, etc, and are the sorts of places you would go to study mineralization processes, internal processes or search for life. They're very different bodies, and there's a very simple dividing line - one that's much easier to calculate/measure than a pseudoscience "cleared the neighborhood" standard.
I hate to bring up our imminent arrest during your crazy time, but we gotta move.
"Nobody ever asks about everyday phenomena" - Feynman complaining about people like you.
And did you exchange a walk on part in the war for a lead role in a cage? - Pink Floyd.
They'll say, "oh, it's okay, there's enough of a size difference between those bodies that they don't count".
No, they'll just point out that while the orbits of the two planets appear to cross when looking at a 2D top-down view of the solar system, in 3D space they come nowhere near each other. The closest point in their orbits is 2 AU apart. Unless you want to say that Neptune's orbital zone its supposed to be clearing is twice the distance between the Earth and the Sun, Pluto is irrelevant.
For someone who seems to care a lot about Pluto you seem to have forgotten how absurdly tilted its orbit is.
I used to get high on life, but I developed a tolerance. Now I need something stronger.