from the pay-attention-to-where-you-leave-things dept.
A giant planet may have "escaped" from our solar system, study finds:
Although Pluto lost its status as "Planet Nine" when it was downgraded to dwarf planet, there is ample evidence that our solar system either had or currently has a large planet far beyond Pluto that may one day claim Pluto's former mantle and become the rightful ninth planet. Unusually regular orbital patterns observed in the Kuiper belt hint that some celestial body more massive than Pluto lurks beyond the distant band of icy debris at the edge of the solar system where Pluto, Eris and other dwarf planets live.
The hypothetical existence of a distant Planet Nine or "Planet X" remains contentious, but evidence continues to mount in its favor. Certainly, it would not be the first time a hypothetical planet was found. Neptune was the first planet found through studying orbits of other bodies in the solar system; intriguingly, its location was discovered with predictions derived from pen-and-paper calculations about telescope observations.
Inadvertently, a recent astronomy paper in Nature found a high likelihood that a gas giant, akin to those in the outer solar system, may have been rapidly ejected from its orbit around the sun early in the evolution of a solar system. The existence of a "lost" Planet Nine early in the formation of the solar system's history would go far in explaining a lot of how and why the solar system looks as it does today.
Journal Reference: Liu, B., Raymond, S.N. & Jacobson, S.A. Early Solar System instability triggered by dispersal of the gaseous disk. Nature 604, 643–646 (2022). DOI: https://doi.org/10.1038/s41586-022-04535-1
(Score: 5, Funny) by Rosco P. Coltrane on Tuesday May 31 2022, @03:25AM (2 children)
You mean "planet IX", now that Pluto has been downgraded, right?
(Score: 5, Informative) by Thexalon on Tuesday May 31 2022, @03:36AM (1 child)
No, they mean Planet X, the last source of alludium fosdex, the shaving cream atom, as discovered by Duck Dodgers in the 24th and 1/2 Century!
But more seriously, my understanding is that Planet X stood for "unknown planet", not "Planet 10", and they were looking for it when they found Pluto and slotted it in at #9.
The only thing that stops a bad guy with a compiler is a good guy with a compiler.
(Score: 0) by Anonymous Coward on Tuesday May 31 2022, @04:41AM
it was way cooler as simultaneously planet X and planet(x)
(Score: 1, Funny) by Anonymous Coward on Tuesday May 31 2022, @12:32PM (13 children)
When they finally find it, just name it Pluto. The compromise that makes everybody happy.
(Score: 0) by Anonymous Coward on Tuesday May 31 2022, @01:01PM (12 children)
They rejected all sorts of reasonable definitions for a planet during the IAU debates, so why do you think they would accept this compromise? I suspect that if a certain group doesn't discover it, or can't point to it and say "see, I predicted that!", then they'll just push for a new definition that carves this one out too and keep looking for another one.
(Score: 2) by HiThere on Tuesday May 31 2022, @01:12PM (11 children)
There is no "reasonable definition of a planet". Not unless you want to consider the asteroids planets. Otherwise it's just a group of orbiting stuff with an artificial boundary, which you can put nearly anywhere. But if Pluto is a planet, so should be Eris, Ceres, Vesta ... the list goes on. The original definition "Lights in the sky that people can see moving" worked fine before there were telescopes (though that one included the moon and the sun as planets).
Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.
(Score: 0) by Anonymous Coward on Tuesday May 31 2022, @01:23PM (1 child)
A reasonable definition would not have demoted nearly every planet in the universe. It was effectively a hit job on Pluto that wasn't very well thought out. There are precisely 8 planets in the entire universe that we know of and possibly 9 total.
It's the byproduct of using the wrong words without really thinking about the consequences. Any exoplanet, by definition can't be a planet ever because it doesn't orbit the sun. They orbit a sun, but not the Sun. A mind-blowingly dumb mistake to make.
(Score: 4, Informative) by Anonymous Coward on Tuesday May 31 2022, @03:52PM
It was an absolute hit job and it was carried out in a very dishonest manner [bbc.co.uk]. They had committees working for quite a while on a new definition to be voted on at the next IAU meeting and they came to a consensus. The vote was to be held at the end of the meeting and you had to be present to vote. A lot of people left the meeting comfortable with knowing what the definition that was being voted on, and the night before the vote the definition was hijacked by the orbital dynamicists (led by Mike Brown) to the mess of what it is now, and they pushed that one through with a lot of dynamicists still present at the meeting because their sessions were near the end. They then claim a great victory despite the heavy thumb they put on the scale and that it was only voted on in the affirmative by 237 out of 10,000 IAU members, so apparently a 2% is enough to declare a mandate.
This whole issue would have been much better served if it was done openly and honestly, and wasn't driven so strongly by one person's ego.
(Score: 4, Insightful) by toddestan on Wednesday June 01 2022, @03:20AM (8 children)
The most reasonable definition for a planet I've seen is a body that has been shaped by its own gravity (in other words, it's big/heavy enough to make itself round), that isn't massive enough to undergo nuclear fusion (in which case it would be a star), and isn't orbiting another planet (in which case it's a moon). So Pluto is a planet, the eight officially recognized planets remain planets, and yes that also makes Eris, Ceres, and Vesta a planet too. But a random irregularly-shaped asteroid isn't a planet.
(Score: 2) by Immerman on Wednesday June 01 2022, @03:38AM (7 children)
Yep, that's my preferred definition. "Big enough to make itself round" seems like a pretty significant and indisputable threshold for a body to cross, and depends only on the body itself. While "cleared its orbit" is heavily situationally dependent, and even arguable.
For example - a couple of gas giants could conceivable toss a small moon into an orbit they had previously cleared. Would that make it a planet? Could you really state *conclusively* that it was the gas giants that cleared the orbit when discovered a billion years later?
Or as I mentioned in another comment - something the bigger than Jupiter far enough out in the outer cloud still wouldn't have enough time to clear its orbit, simply because everything orbits so slowly. I really want to see the person who argues that a super-Jupiter isn't a planet.
(Score: 0) by Anonymous Coward on Wednesday June 01 2022, @04:02AM (1 child)
"Clearing its orbit" was the gerrymander used to demote Pluto, but as you note, it was not a very good choice ("has to orbit the Sun" was very shortsighted as well).
(Score: 0) by Anonymous Coward on Wednesday June 01 2022, @04:14AM
I could see the addition of exoplanet, but that seems a bit labored unless there turns out to be significant differences with this solar system to warrant the distinction.
(Score: 0) by Anonymous Coward on Wednesday June 01 2022, @11:10AM (4 children)
"Big enough to be round" is too loose of a definition because it leads to dozens, probably hundreds, and maybe thousands of "planets." There might be a whole lot of Sedna-like objects out there. There is a very obvious difference between some random KBO and a real planet like Earth.
That difference is the "cleared its orbit." The wording is terrible but the definition is good. The problem with the wording is that people immediately say "but the orbit isn't clear, there are near Earth asteroids, Trojans and whatever else." And that's true!
But what the definition actually means is that the object in question dominates the orbits in question. All those near Earth asteroids are in resonance with the Earth. Trojans are in the Lagrange points created by the planet. Even the things that don't orbit the planet directly are still controlled by it, and the planet is the most massive object in the area by far. Earth is millions of times more massive than all the near Earth asteroids put together. Pluto is about 10% of the total mass of the Kuiper belt. Ceres is only about 1/3 of the mass of the asteroid belt. Neither of them has a significant influence on the orbits of the many similar objects. The Kuiper belt is more affected by the gravity of Neptune than of Pluto, and the asteroid belt is more influenced by Jupiter and Mars than by Ceres. Anyone who doesn't recognize this difference either doesn't understand the situation or just doesn't want to admit it.
(Score: 1, Interesting) by Anonymous Coward on Wednesday June 01 2022, @01:41PM (3 children)
Do, how do you rationalize the requirement that a planet must orbit the Sun. As in our sun. Face it, they were in such a haste to denote Pluto that none of this was well thought out.
(Score: 1, Interesting) by Anonymous Coward on Wednesday June 01 2022, @11:03PM (2 children)
If it doesn't orbit the Sun, then it's not a planet, it's an exoplanet.
While there's probably no physical distinction, they are different enough in terms of how we study, talk and think about them that they definitely deserve different words.
(Score: 1, Interesting) by Anonymous Coward on Thursday June 02 2022, @12:29AM
Here's an example made of two hypothetical news article headlines :
"Astronomers discover new planet"
"Astronomers discover new exoplanet"
See how those mean different things?
(Score: 3, Interesting) by toddestan on Thursday June 02 2022, @03:14AM
The whole clearing their orbit thing is tough for exoplanets, because it's going to be really hard to determine whether they have actually cleared their orbit from light-years away. So if you're going to use something silly like that to define a planet, you might as well just say that they must orbit The Sun too, because it's impossible to tell whether any other those large objects orbiting other stars are actually proper planets that have cleared their orbits, or if they are just really big pieces of debris.
(Score: 0) by Anonymous Coward on Tuesday May 31 2022, @02:00PM
It was kind of lost for a while, but then I looked under the couch cushions, and whaddya know?
(Score: 3, Informative) by Immerman on Tuesday May 31 2022, @02:21PM (3 children)
It seems to me very unlikely that such a Planet 9 could exist. Not that there couldn't be some huge object out there, the evidence for that is growing - just that it would no more be a planet than Pluto is.
A planet has to clear its orbit of other non-captured objects, right? That's the whole reason Pluto isn't regarded as a planet under the new definition.
And given the chaotic orbits of the trans-Neptunian (and further) objects we've found so far, and the extremely long orbital periods of anything out far enough to not have been spotted yet, it seems very unlikely that even a Jupiter-sized object would have been able to clear its orbit. So... not a planet.
(Score: 0) by Anonymous Coward on Wednesday June 01 2022, @11:22AM (2 children)
I do not think Planet Nine exists, and if it does, it isn't likely to be be much more massive than Earth (and it's definitely ruled out that it's more massive than Neptune). But that doesn't mean that it wouldn't qualify as a planet. The whole reason people are looking for it is because the scattered disk objects seem to have orbits that look like they're influenced by a much more massive object. That's exactly what the definition means!
Personally, I think there used to be a brown or even a red dwarf out there a couple of billion years ago, it orbited the Sun long enough to set up all those orbits, but then a passing star knocked it loose, and now it's floating around the galaxy somewhere, lost to time and space. This is not very different from the situation with Proxima, which is only just barely attached to the rest of Alpha Centauri, and will probably become unbound at some point if it in fact has not already.
(Score: 2) by Immerman on Wednesday June 01 2022, @01:29PM (1 child)
Scattering objects is insufficient - Pluto has no doubt scattered plenty of objects itself. Clearing its orbit means it has to have done so much scattering that there are no longer any more objects for it to scatter - they've all either collided with it, been cast into the sun/interstellar space/other planets, or had their orbits further influenced by other planets to establish an orbit that no longer approaches the original planet.
(Score: 0) by Anonymous Coward on Thursday June 02 2022, @12:27AM
When I talk about the "scattered disk," I mean the objects that are in orbits outside the Kuiper belt but too close to be part of the Oort cloud. This region is known as the scattered disk. There are the objects whose orbital peculiarities imply that Planet Nine might exist. Sometimes astronomers prefer to distinguish between the "scattered disk" proper, which is outside the Kuiper belt but still close enough to maybe be influenced by Neptune, and what they call "detached" objects, which are too far for any influence from Neptune but still might be influenced by Planet Nine. Personally I don't think that's a good distinction to make because the boundaries are blurry and calling them "detached" implies that they aren't orbiting anything.
Read my other post for the explanation of why "cleared its orbit" doesn't mean what you think it means.
(Score: 2) by Reziac on Wednesday June 01 2022, @02:26AM
....Plan 9.
And there is no Alkibiades to come back and save us from ourselves.