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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.
#fuckbeta #iamslashdot #dicemustdie
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.
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
... 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.
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.
Assorted stuff I do sometimes: Lemuria.org