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."

Comments

IAU? Haste? No way.

[girlintraining]

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.

Re:IAU? Haste? No way.

[starless]

Why do you call the committee members pseudo-scientists? I'm rather sure everyone has a PhD in astronomy/astrophysics. (I'm technically an IAU member, although I've had little involvement with it.)

Re:IAU? Haste? No way.

[Doubting Sapien]

I'm a Christian Scientist, you insensitive clod!

Re:IAU? Haste? No way.

[lennier]

But then, I'd expect nothing less from a committee of pseudo-scientists

You, sir, have very low expectations for the noble profession of pseudo-science. I both demand and expect a whole lot more from my committees of space pseudo-scientists:

1. At least three separate and conflicting theories about the catastrophic formation of the solar system as a result of an interplanetary war between four and eight thousand years ago.
2. A dozen formulations of the Lorentz Contraction as a result of the pre-Einsteinian ether
3. A gigantic laser mounted on Mimas
4. A baroque dying Martian civilisation clustered in glorious decadent splendour among the Red Weed entwined canals and pentagonal pyramids of Cydonia.
5. Ancient space Egyptians and Mayans with lasercats.
6. Space Mormons versus robots.
7. A literary analysis of Shakespeare's Hamlet as really being about the precession of the equinoxes.
8. An apocalyptic prediction involving Halley's Comet.
9. An Electric Universe theory, preferably one that makes Saturn a former star.
10. A homebuilt antigravity demonstration device harnessing the awesome power of magnets.

Re:IAU? Haste? No way.

[starless]

Why do you call the committee members pseudo-scientists? I'm rather sure everyone has a PhD in astronomy/astrophysics. (I'm technically an IAU member, although I've had little involvement with it.)

They don't experiment. They don't work in a lab. They may be involved in the scientific community, but they're not doing any scientific work per-se. They're bureaucrats with training in science.

Can you specify some names so I can check this is really true?
(Not many of us astronomers work in labs or experiment anyway. We mainly obtain and analyze data, construct theoretical models. A smaller number of us work on instrumentation which might involve working in an actual lab.)

Re:IAU? Haste? No way.

[girlintraining]

Astronomical knowledge is evolving quite a bit faster than the rest of the library. I'm not necessarily saying that any IAU decisions are correct but I don't see anything fundamentally wrong with recategorizing. Isn't it that a hallmark of the intelligent?

No. I can write a computer algorithm to sort something; that doesn't make it intelligent. Anyone can make something more complicated -- true genius is making things simpler.

Re:IAU? Haste? No way.

[GrumpySteen]

It would be virtually impossible to name names. The reclassification of Pluto (among other things) was the result of a vote held at the end an IAU General Assembly where only 424 out of roughly 9000 members actually voted.

Re:IAU? Haste? No way.

[Tim the Gecko]

No, it's a hallmark of the bored with too much free time. If you had an employee who spent most of their time recategorizing rather than coming up with something new, would you consider them intelligent? You'd probably think they were lazy or incompetent.

The implication here is that people just got bored and changed things, but really it's just like the planet-to-asteroid naming change in the 1800s. People find a new planet (Ceres/Pluto), and after a while find a whole lot of similar objects. You probably don't want to learn a whole lot of asteroid or KBO names.

Added to this, our notions of Pluto have gradually dwindled from a huge pitch-dark planet, able to perturb the mighty Neptune in its orbit, down to a small bright billiard ball with a gravitational pull only slightly bigger than that of yo' mama.

Re:IAU? Haste? No way.

[jythie]

Yes they do.

The IAU, both committee and members, is made up of active scientists who do the bureaucratic stuff in addition to their research jobs. That is how professional organizations usually work, the people running them are doing community duty above and beyond their paid employment.

Re:IAU? Haste? No way.

[Will.Woodhull]

Actually working astronomers do a lot of lab work. They do spend a good bit of time refining theoretical models, but a lot more time working out ways to test those models with existing laboratory equipment. Some of that equipment is now in orbit and much of the remainder is in "observatories". You know, research laboratories with telescopes instead of microscopes.

Astronomers are also a very resourceful bunch who are continually looking for ways to test their theories against laboratory observations that have already been done. If you can find what you need to test a hypothesis in last year's download of Hubble material, or the digitized images of telescopic photos taken in the 1930s, that still counts as laboratory research.

Re:IAU? Haste? No way.

[jythie]

LInguists would laugh at this, if for no other reason then they change the technical definition not the common one, so your whole complain is a straw man.

The only reason the Pluto stuff (and the IAU) has gotten so much attention and ranting is that an American discovered Pluto and a bunch of patriots got butthurt that 'europeans' were taking away their thunder.

When there is ambiguity, professional and standards organizations redefine stuff all the time. This was a pretty routine thing to do and would have gone completely under the radar if nationalism had not come into play and got people fired up. In the end, they couldn't keep Pluto as a 'planet' without including a significant number of other bodies, which would have pissed off people too.

But like many issues, the original energy behind the backlash has been pretty much lost on the people who continue to push it today....which was part of the point. You can wrap up all sorts of nationalistic bullshit if you tie it into other existing narratives that appeal to the same people... think of the children, elitists forcing things on the public.. plays to the same audience and plays well off even less knowledge of the issue.

Re:IAU? Haste? No way.

[chebucto]

true genius is making things simpler.

Or rather, true genius is making things as simple as they can be but no simpler.

Speaking as an amateur, it seems that adding the 'minor planet' category was a reasonable decision. Charon & Pluto are distinct from asteroids, but quite a lot smaller than the rest of the bodies we call planets.

In other fields, we distinguish between islets and islands, streams and rivers, bushes and trees, etc etc etc. Not to add complexity, but to more fully describe reality.

Re:IAU? Haste? No way.

[osu-neko]

Wow. Pretty much all completely false. Nearly all of the 9000+ members of the IAU are working astronomers actually using the scientific method. The whole process of deciding on the definition of "planet" was a peer driven. The objections were from a minority who were outvoted. The guy who discovered Eris, and had his own discovery demoted into non-planet status by the decision, admits it was the right decision to make. ("It was hard not to mourn the loss of my now ex-planet, except for the fact that I had to admit that kicking it out was the most scientifically sensible thing to happen to planetary classification since asteroids were also kicked out almost 200 years ago.") Far from arbitrary, it follows the very same rationale that was used to demote Ceres two hundred years ago, keeping the definition of planet as what we decided back then rather than expanding it in ways that would be incompatible with that. Alas, being consistent meant we need to correct the mistake we made with Pluto to begin with. In any case, it wasn't a proclamation by poseurs, it was the consensus of the working astronomers who actually do the work. The ones you want to load into your cannon include the very scientists making lasting contributions to the field. I think discovering Eris was contributing to the field, not sure why you insist people doing stuff like this should be shot into a passing asteroid. I understand you're emotionally upset about Pluto, but making up a largely false story about what actually happened here is silly...

Re:IAU? Haste? No way.

[Anonymous Coward]

Working astronomer here (radio, ground-based). I spend about 2-3 weeks per year actually at an observatory. That's roughly typical in this field, though there's a lot of variation: some people work more on the engineering side and spend 90% of their time on-site, while pure theoreticians might never see a telescope.

Sun is the same way

[mister_playboy]

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.

Re:Sun is the same way

[mooingyak]

If the mass part counts at all (Charon being 12% of Pluto's mass), Jupiter is a far smaller fraction of the Sun's mass (something like 0.1% if I did the math right).

Barycenter based definition has issues

[Anonymous Coward]

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.

Re:Now it makes sense

[spire3661]

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.

Pluto never was a planet

[TheGoodNamesWereGone]

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.

Re:Pluto never was a planet

[Anonymous Coward]

"Is it something more personal between individuals in astronomy?"

This, actually. Long story short, there are two camps of astronomers. One of them characterizes bodies based on where they're orbiting, the other characterizes bodies based off what they're made of.

The former pushed this through as an act of political dickmanship on the last day of a conference (after most participants had gone home), in a only tangentially related addition to a talk scheduled for a different topic, breaking IAU rules to do so. It's not a 'scientific' decision, it's a purely political one.

And any definition that has a category 'dwarf planet' that isn't a subset of 'planet' is about as stupid as redefining 'car' so that 'electric cars' are no longer a subset of 'cars'.

Re:Pluto never was a planet

[Baloroth]

To say it "never was a planet" is not quite true. It never was a planet according to the definition of planet that we use now, but it was a planet according to the definition we used to use. If you change the definition, people are going to be confused. It has nothing to do with tradition (except insofar as language is a "tradition"), and everything to do with the alteration of the language. Now, that alteration may be fully scientifically justified and acceptable... but it's still going to annoy people.

The comparison with the geocentrism is a little faulty. The issue here has very little to do with our knowledge of reality changing (it didn't really), but with the way we look at that reality changing (i.e. the words used for a thing).

It's not science, it's linguistics. The result is even now what category Pluto falls into can be debated: we could quite easily call it a planet even now, the problem is the definition would be too wide and force us to call things planets not traditionally called planets. So somewhat contrary to your point, a large part of the reason Pluto isn't called a planet anymore is actually tradition: because we don't want to call all the Kuiper belt objects planets also.

Re:Pluto never was a planet

[TheGoodNamesWereGone]

I figured it had something to do with dick-waving. I'm not a professional astronomer, don't play one on TV, but I've had an abiding love for the subject since I was growing up in the 60s. If you use the orbital argument then it makes sense, because Ceres, too was thought to be a planet in 1801 (It accorded nicely with the 'traditional' Bode's Law). It didn't take long for the scientific community to figure out thought, after Vesta, Juno, and other asteroids were found that these were just the largest members of a population of many; we now estimate hundreds of thousands. Likewise the compostional argument works in favor of demotion as well. Working outward we have rocky inner planets, two gas giants, two ice giants, and then a buttload of comparitively very tiny solid icy bodies, that when they get perturbed and wander closer, get called comets. I don't understand the emotion behind the debate. in 1801 the asteroid belt wasn't known, so they called Ceres a planet. In 1930 the Kuiper belt wasn't known, so they called Pluto one. We've learned differently. What's all the fuss?

Re:Now it makes sense

[idji]

because you want results in seconds, not aeons.

Re:Now it makes sense

[canajin56]

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".