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Is Pluto a Binary Planet?
astroengine writes "If the Pluto-Charon system were viewed in a similar way to binary stars and binary asteroids, Pluto would become a Pluto-Charon binary planet. After all, Charon is 12% the mass of Pluto, causing the duo to orbit a barycenter that is located above Pluto's surface. Sadly, in the IAU's haste to define what a planet is in 2006, they missed a golden opportunity to define the planetary binary. Interestingly, if Pluto was a binary planet, last week's discovery of a fifth Plutonian moon would have in fact been the binary's fourth moon to be discovered by Hubble — under the binary definition, Charon wouldn't be classified as a moon at all."
The IAU has been trying to redefine things in bulk, and then growing discontent with those definitions and changing them yet again. It's a far cry from the organization's original role: Cataloging astronomical objects. To put it in perspective, they're like a librarian that changes the layout of the indexing system weekly. They don't actually move the books around, but they rename the aisles, recategorize things, and generally make a massive mess of it all.
But then, I'd expect nothing less from a committee of pseudo-scientists; They're so engrossed with their own administrations they've become cut off from the people they're supposed to be helping.
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As closely as they orbit each other, I'd say Pluto-Charon would be almost the example of such a system. Heck, it's almost a Rocheworld. :p
The barycenter of the Sun/Jupiter system lies at 1.07 solar radii from the Sun's core (i.e. outside the Sun). Is the Sun a binary star?
For those curious, the barycenter of the Earth/Moon system is well inside the Earth, despite the Moon relatively energetic orbit.
Do what thou wilt shall be the whole of the Law
The issue with using the barycentre, is by moving two objects further apart without changing the mass, eventually the barycentre will be above their surfaces. The Jupiter-Sun barycentre is above the surface of the sun, but wouldn't be if Jupiter were closer. The Earth-Moon barycentre is about 75% of the radius of the Earth, but if the distance between them increased by about 25%, then the Earth-Moon barycentre would be above Earth's surface. So it is quite possible to have two bodies that are very influential on each other, but with the barycentre below the surface due to being too close. And the status could change simply by having one body move further away, like Earth's moon is currently doing.
Ugh. The entire idea of the 'death star' shows how little imagination Lucas has. Even moving the death star into a system would effect the planetary orbits. Why would you need a big laser gun when you can simply wobble a planet out of its habitable orbit using the gravity of your space station.
Good-bye
I do not understand at all the rage over Pluto's demotion from planetary status. Is it tradition? 'Traditionally' the Sun was thought to revolve around the Earth. Is it because children have to be sat down and gently told the truth, like about Santa Claus? Is it something more personal between individuals in astronomy? It's called *science* folks, and it's self-correcting. I just don't get why people are so upset.
My proposed definition: A binary system comprises two objects whose common center of gravity is above the surface of either object and the components of the system are similar in size and/or mass. This would Pluto-Charon a binary system and the Sun-Jupiter not a binary system.
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because you want results in seconds, not aeons.
Because Pluto is not a planet.
Binary dwarf planets, sure. That seems a reasonable argument. But even treating Pluto and Charon as a single entity can't upgrade them to planet status.
The first death star was 160 KM in diameter, so a radius of 80 KM. If you assume the same mass density as, say, an aircraft carrier or other military vessel (about 0.15 kg/m^3), you end up with a Death Star that masses about 3e14 KG. That's absurdly heavy to realistically have engines zipping it about, but it's not going to result in major and instantaneous disruptions of orbits. Even Mars' tiny moon Phobos has 100 times the mass. Although the Death Star II from RotJ was supposed to be 900KM across, so that would put it about even with the mass of Phobos. Put another way, the Earth masses 10,000,000,000 times as much (or only 100,000,000 for the Death Star II), so I don't see how the Death Star is going to be winning that gravitational tug-of-war. If you want to argue "Well maybe they have super cool tractor beams so they can amplify their gravitational pull and their massive engines can keep them stationary while they're doing it!" the obvious counter is "They don't, that's why they went with the laser, since they thought about it. Also big laser is more menacing in a platform which has the primary purpose of intimidation. Additionally the big laser doubles as a way to destroy enemy capital ships from well outside their own engagement radius".
ASCII stupid question, get a stupid ANSI
"The Death Star was so massive that when it orbited a planet it became a binary system."
But of course it's a binary system: that's no moon.
And can we please now get back to important things like arguing about whether C is a low level language?
OK, just for you. :D Here goes:
Of course it is a low level language. It was described (by Ritchie, if memory serves - in any case one of the authors/designers) as "a structured PDP-11 macro assembler". I would argue that, by definition, any 'assembler' is a low-level language. I would go farther - any language in which the primary semantics and syntax of the language is closely aligned with the physical movements of data through memory, and operations upon that data, is a low level language - freely admitting that this assertion is a bit of hand-waving, but still has some relevance to the meaning. In other words, if almost everything in the language has to do with loading and, storing single bits or rectangular arrays of data, and arithmetic and logical operations on that data, it's a low level language. (I'm trying - probably badly - to elicit an analogy from the language to the machine operations that are executed as a result.)
By contrast, as one of the early designers of SQL discovered at IBM in the early-mid 1970s noted, "We found that a single sentence of SQL could result in 250,000 machine instructions being executed - that explained why it was so slow." Another primary characteristic of SQL is that one can not easily say by inspecting the code just where in a computer's memory a particular data item is stored. (That particular criterion has been greatly complicated by the rather amazing manipulations of cacheing, threading, multiprocessing and so forth, that used to be part of the operating system (and written in low-level language), and are now in hardware and essentially written in a hardware description language, which is a kind of descendant of C.
So, will that do? I am out of popcorn but I'm on the way to the store. I'll bring some back! :)
It's easier to be a result of the past, but more fun to be a cause of the future! http://www.spacefinancegroup.com/
No, the problem is that if you make being a spheroid sufficient to call an object a "planet" (that, and orbiting the Sun rather than another planet), then instead of 9 planets, suddenly you get a bunch more because you'll have to reclassify the other spheroid sun-orbiting objects (now called "dwarf planets") as full-fledged planets, including Ceres, Eris, Haumea, and Makemake. Don't forget a few other: Orcus, Quaoar, Sedna, and 2007 OR10, which may very well be classified dwarf planets soon, and there's probably more out there we haven't found yet (that latest one was just discovered in 2007), so we'd be teaching kids increasing numbers of planets all the time.
Even if we kept the "dwarf planet" designation and set Pluto as the lower limit, Eris is both larger and more massive than Pluto so we'd still have 10 planets (until any larger ones are discovered way out where Eris is).
... since the orbit of Pluto crosses that of Neptune and therefore Neptune has not cleared out its region of space yet, and probably never will.
No, the orbit of Pluto never crosses that of Neptune. Really. Sometimes Pluto is closer to the sun than Neputune is, but the two orbits never cross. You have to think in 3D here.
But "clearing the orbit" is a stupid argument, nevertheless. By that measure, we have one planet in the solar system, and that's Mercury. All the others have various debris floating around in their orbits, especially near the Lagrange points 30 degrees ahead of and behind them.
And Mars wouldn't compete for a planetary title at all - its orbit is mostly clear because of Jupiter and Earth, not itself - it's just too small to keep its orbit clear on its own.
I think the actual reasoning behind demoting Pluto is that a camp of astronomers want a fixed number. So you take the classic planets known since the antique, and add Uranus and Neptune because they're too friggin' big to be ignored, and leave it at that. Then you make up rules that would pass your eight and block any others.
The 3:2 orbital resonance and relatively high inclination of Pluto's orbit guarantees it's never close to Neptune. The orbits DON'T CROSS, Pluto is well out of the ecliptic plane when its orbit comes closer than that of Neptune. From the point of view of Neptune, it still has the orbit all to itself. This is somewhat similar to Trojan asteroids and Jupiter. Though they share the same rough path around the sun, the asteroids stay clustered around points 60 degrees ahead of and behind Jupiter. They're never close to Jupiter, as this would disrupt them out of their orbits. The only ones that remain are those that orbit in such a manner that they don't have to come dangerously close to Jupiter. Even then, future perturbations mean some of them will probably be ejected or collide with Jupiter eventually.
How is the Riemann zeta function like Trump rallies? Both have an endless number of trivial zeros.
You could argue that Sun-Jupiter is some kind of Binary, based on that definition. You need something that enforces a near-equal mass - and by near-equal, maybe order of magnitude mass. Whether you write that as it, or abstract it - like having the barycentre greater that ?.2*orbital radii(or semi-major axis) from either planet.
The truth is, we don't have any closely-studyable examples of something we would really describe as a binary planet. Some asteroids are in binary systems, I think, but nothing substantial. When we are clear that we have a binary planet somewhere - or better still, several examples, so we know what is typical - we can make that the 'reference specimen', to borrow from biology. Until then, happity guessing.
Prediction for end of Universe #42: Fencepost error in Quantum_bogosort.cpp
Oops. Someone failed Percentages. The mass of the moon is a bit less than 1/80th of Earth's mass. Or 0.0123, which is 1.23%.
The Moon is also about 5 times Pluto's mass, and around 50 times Charon's estimated mass. If Charon gets to be a planet, the Moon should be too. (And the Galilean moons, and Titan...)
Science is all about firing a drunk pig out of a cannon just to see what happens.
There is a startling amount of ignorance in this thread. Pluto was demoted for a simple reason -- we found another body that is bigger in mass. So the IAU was faced with a stark choice. Add another 3 or so planets (there are several objects similar in mass, just one larger so far) with more likely to come, that are in weirdo orbits (kinda like pluto actually). Or demote pluto. Astronomers took their lumps and finally formally acknowledged that the largest Kuiper belt object does not deserve planetary status any more than the largest asteroid does.
No. Pluto is a dog.
What I love about /. is that a topic like this can get almost 200 comments (at the time of this posting).
Most of my friends, even the geekier ones, would go "uh, ok, so what?". Because today "geek" has become to be limited to computers and that was never the gist of it until recently.
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