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Mass of Dwarf Planet Eris 27% Greater than Pluto
jcgam69 writes "When it was discovered in 2005, some thought Eris should be considered the 10th planet of our solar system. Everyone still considered Pluto a planet then. At first, Eris was thought to be slightly larger. Now — with the help of Eris' moon — Eris is known to be 27% more massive than Pluto. If Pluto had remained a planet to the entire community of astronomers, surely Eris would be considered the 10th planet."
Poor lonely Pluto;
No one loves you now but me.
And Clyde Tombaugh's urn.
My Very Excellent Mother Just Serverd Us Nine Pizzas- Excelsior!
All Hail Discordia!
Hail yes!
fnord.
...our beloved ninth planet just got plutowned!
This message printed on 100% post-consumer recycled electrons.
it's a planet. If it's orbiting a larger planet, then it's a moon.
This is just a classification problem. In my company, the secretary takes care of that shit. WHY ARE WE wasting our time with this crap? I don't give a shit if some schoolkid has to memorize dozens of planets. That's between him and his teacher.
Fascism trolls keeping me up every night. When I starts a preachin', he HITS ME WITH HIS REICH!
Pluto is big enough to have a moon (okay, so Pluto/Charon is really a double planet). Eris is more massive than Pluto. Sounds like they should both get to (re)join the club. Why not?
Paleotechnologist and connoisseur of pretty shiny things.
Some of us still consider Pluto a planet.
What does it matter what its classified as? Its still a big frozen chunk of rock in the middle of nowhere. I guess the only difference is if it will be taught in school.
Libertarian Leaning Political Discussion Forum.
You see? You see? Your stupid minds...stupid! Stupid!!
(Okay, so it's "Eris" and not "Eros". Sue me.)
Modern copyright is theft of culture from everyone and it retards the progress of the useful arts and sciences.
The Kuiper belt, I am sure, contains still some surprises for us. Perhaps many surprises, and who knows, maybe some of them unpleasant. I wouldn't be surprised if Neptune one day grabs one of those rocks and launches it over here. That'll be lots of fun.
"The agriculture ministry is not in charge of Gundam" - Japanese ministry official.
You got it wrong, that's Uranus.
Send email from the afterlife! Write your e-will at Dead Man's Switch.
That Mondas is the 10th planet. Duh.
.. the planet is defended by 5 lions.
"I like to lick butts!" by MobileTatsu-NJG (#32700246) (Score:5, Informative)
Xena was never more than an unofficial nickname. No one, including the person who discovered it, ever intended for Xena and Gabrielle to be the official names for this pair of heavenly bodies.
Remember: just now they figured out which of Eris and Pluto is more massive...
but they also know the internal density distributions of extrasolar planets that barely take up a pixel on the most powerful telescopes.
Apology to Ubuntu forum.
It's funny how people get so worked up about Pluto not being a planet. The fact is that it should have never been a planet in the first place. Scientists did a similar thing back in the 1800s when the decided not to call all of the asteroids between Jupiter and Mars planets. If we kept calling Pluto a planet, then we'd have to add all the other Kuiper belt objects. There's a very good Scientific American article here that explains the whole thing. If you're still crying about Pluto not being a planet you should probably read it.
-1 (Troll) is antihammer
But I've always defined a planet as a solid body whose gravitational field was sufficient to force it into a spherical shape and strong enough to maintain some sort of atmosphere. I suppose that would kick Mercury out of the planet club as well, but we would welcome Titan with open arms.
"Never let your sense of morals prevent you from doing what is right" - Salvor Hardin
Poor lonely Pluto;
No one loves you now but me.
You actually aren't alone. These guys were so moved with affection for Pluto that they created a music video. Rock on, Pluto!
Gravity provides the centripetal force needed to keep satellites in orbit. If you focus on the simple case of circular orbits, you can use the centripetal force formula with the law of gravity to determine the mass of a planet. Simply set the force of gravity equal to the centripetal force and solve for the mass of the planet M.
M = r * v^2 / G
The period of Eris' moon provides another way to calculate its mass.
Period T = 2pi * sqrt(r^3 / G*M)
Thus I imagine the various images of the moon provided a way to calculate its period and indirectly determine the mass of the central body.
However the article doesn't give any specifics. It would be interesting to know what methods they used and the degree of accuracy of their measurements.
JJ +
This is science we're talking about. 'Grandfathering' a planet would be like declaring 1 a prime because it was treated as one in the past. If we did this, we'd have to start explicitly making exclusions for the grandfathered planet/number ("all planets except Pluto are...").
Consistency is important in science.
Consider the image of a hard packed snowball, broken into two unequal parts.
So goes the latest theory about this 'planet' Its size, if the two pieces were weighed together,
would make it a considerable planet in its own right. But if it is broken in two because it is
made of mostly ice and lighter elements, would we consider it to be a planet at all or just
another large body out in the Ort Cloud?
"Sorry. No Refunds."
Biased American astronomers prefer to claim Pluto as a planet(since it was an American discovery). Lazy students prefer to remember less names. Slash dot prefers to keep putting salt in The Wounds of those astronomers who preferred to keep Pluto as a planet.
Now calling me an idiot would make you feel better go ahead. At least I am not a Rocket scientist....
Keep in mind, there are those of us who consider the definition of a planet as wrong, and the 'reclassification' as merely an attempt to exclude Pluto as a planet for the sake of scientific contrariness.
What are you talking about? I haven't considered it a planet since I took astronomy in the early 90's. Of course the public didn't have a clue, but a lot of astronomers knew Pluto shouldn't be considered a (regular) planet.
If you believe it is not a planet, then you have earned the title. If you accept that it IS a planet, then no 'name calling' will apply.
---- Booth was a patriot ----
As an example I was watching some random evangelical show late one night (I had insomnia) while the main debate was going on. There was a whole segment dedicated to how scientists "didn't know" whether Pluto was a planet or not and how this clearly meant that they couldn't possibly make definitive statements on things like evolution and so forth. Of course to anyone involved in science the flaw in this argument is obvious - and neatly serves to indicate how the "planet" label isn't really that significant from any technical point of view.
I think the mistake in the logic here is assuming that Pluto was kept a planet because it had a certain mass, or orbit, or whatever. Pluto was kept a planet because of tradition, in essence. If it were found today, I don't think it would be considered one. So no opening of the floodgates for every hunk of rock that has some number that measures larger than Pluto.
yeah, uhh..since when did size determine if something is a planet?
dreemkill.
Pluto and Eris prefer the term "Gravitationally Challenged".
General Relativity: Space-time tells matter where to go; Matter tells space-time what shape to be.
I demand that we also "grandfather" in Ceres, Pallas, Juno, and Vesta, for historical reasons.
Some of us still consider them to be planets, and are really getting sick of the jackasses who keep changing their names (minor planets? asteroids? dwarf planet?)
Also, it dawns on me that all non-stars are planets (though not planets simpliciter) by this system of classification, so, this line merely distinguishes between major and minor planets.
On that note, it would probably also be useful to distinguish first between bodies at rest upon other bodies (like me and this computer) versus bodies in freefall (like all the forgoing bodies), for I'm uncomfortable with myself being classified as either a star or a planet. We could call the latter "celestial" bodies and the former, say, "terrestrial".
-Forrest Cameranesi, Geek of all Trades
"I am Sam. Sam I am. I do not like trolls, flames, or spam."
Yeah, but Pluto got voted out... so now.
My Very Excellent Mother Just Served Us NOTHING!
You know, Pluto had a good thing going until these stupid other transneptunian objects started to to clutter sky and make people turn on poor little Pluto. It's like being able exploit a flaw in a game. It works great for a while, but then a bunch of people do it and you're screwed.
It is no longer uncommon to be uncommon.
"Mass of Dwarf Planet Eris 27% Greater than Pluto... surely Eris would be considered the 10th planet." If that's all it took, then my ex-girlfriend would be classified as a planet as well!
Schatten Teufel
There is nothing "Common" about Sense
Wasn't the Trojan War started because she wasn't invited to a party? And now, not only is she not invited to join the planets...but we're calling her FAT?
You're example fails to prove your point as 1 IS considered prime by some.
But, even using your example, your example fails. If you knew anything about number theory you'd realize that 1 HAS to be treated as a special case in... many proofs.
"It's barely enormous!"
"It's merely huge!"
A feeling of having made the same mistake before: Deja Foobar
If they can be inconsistent for electrons, why can't they be for planets?
What if Tetris was invented by Nazis?
...for Astronomers, Size Matters.
That's not Eris or Pluto...it appears to be a black hole.
Pluto won't clear its orbital path in the lifetime of the sun for a few reasons. The Kuiper Belt (where Pluto resides) is a very excited region of the solar system in terms of orbital eccentricities and inclications, which results in a very high mean impact velocity between objects out there. This means impacts tend to be destructive rather than letting anything grow larger. Additionally the number of particles in the Kuiper belt is sufficiently small impacts are fairly rare. Basically, the Kuiper Belt never became a planet for much the same reason the asteroid belt hasn't.
Regarding the two planets bit, that's a highly unstable orbital configuration. If they orbited a common center of mass (like the Earth and moon) it would be feasible, but then we'd just call them a twin planetary system, or the smaller of the two would be considered a moon.
Eris dies.
Balderdash!
I find this to be highly illogical and foolish. How can you say that with a planet nearby called URANUS? The joke is as old as the name. Clearly, you are either clueless to astronomy, or a troll.
Personally, Pluto shouldn't be so down. It has confirmed land. Jupiter, Saturn, Uranus (or as it will later be known, Urectum), (and possibly Neptune) do not. "Hey Jupiter, I bet you can't wait to have someone land on you and plant a flag... oh, wait, that's right. YOU CAN'T!" "Hey, Saturn, look what I can do. Notice all this SOLID I can do, hmm? Why don't you give it a try sometime!"
27% Greater than Pluto
I don't believe any statistic about a planetoid named after the Goddess of Disinformation.
"There's lies, damn lies, and statistics...and then there's Discordians."
i'd hit it so hard, if you pulled me out you'd be the king of britain [bash.org]
Eris would *not* be considered the 10th planet.
And don't call me Shirley.
thatsalottamassive!
Also, the combined mass is not sufficient to clear its orbit. (Otherwise it would have done so already.)
So what happens when Eris is in my sign? WTFBBQ!
Isn't enough that I ruined a pony, making a gift for you?
I came in here looking for this exact comment, and am not disappointed to see that One Of Us managed it on the third post.
Also funny that you are modded to 5. Fnord.
Weaselmancer
rediculous.
Why? The actual physical and astronomical facts about the matter, given our contemporary understanding of astronomy, do not depend on such a classification at all. The classification of the celestial objects is not a matter of convenience, not of fact. No astronomical fact follows independently from the "fact" that body X is classified as a Y in your scheme. That is, the only facts that follow about body X are the very same facts that the classification requires for it to be an X; when you gather all the facts that you need to classify X as a Y, the fact that X is a Y does not allow you to infer further facts about it.
Because, of course, there are no physical or astronomical law hinges on whether an object is a star, planet or moon; they're just big blobs of matter in various states, of various shapes, moving at various velocities relative to each other, and exerting all of the usual forces that they exert in virtue of being the aggregates of the stuff they are made out of.
Are you adequate?
First, a quick response to your proposal: LOTS of things have moons. There are quite a few non-round asteroids (not big enough to gravitationally collapse) that have moons. In general, if any of us here in the peanut gallery have a proposed definition that sounds even vaguely plausible, it's a good bet that the professional astronomers have not only thought of it years ago, but also figured out solid reasons why it wouldn't work.
Speaking of asteroids, I'd like to remind everyone that for most of the 19th century, there were over 10 officially recognized planets. In addition to the classical planets Mercury, Venus, Earth, Mars, Jupiter and Saturn, they had Uranus (1781), Ceres (1801), Pallas (1802), Juno (1804), Vesta (1807), and finally Neptune (1846). The same improvements in optics that led to the discovery of Neptune also pointed out several other planetary bodies. Then dozens. Then hundreds, all coorbital with the four between Mars and Jupiter, forming a vast ... belt, of sorts.
You can guess what happened next (hint: you weren't told to memorize 13 planets back in grade school). The relevance of this tale to Pluto is left as an exercise for the reader.
I find it ironic that you question my knowledge of number theory, as it's a field I've done research in. I realize that 1 must be treated as a special case in many proofs, thus the widespread use of the term "nontrivial", but thankfully, it does not have to be invoked every time a proof involving primality arises. That is what I was trying to illustrate.
As for considering 1 a prime, I suppose that's a question of opinion, but it doesn't really obey enough properties of the primes to warrant that designation in my mind (or the minds of most mathematicians, as far as I know). For instance, it's not relatively prime to any other primes - something that can be said of every other prime number. It's a very nice thing to say that any two distinct primes are coprime, and declaring 1 prime screws that up.
Don't tell the Scientologists: Xenu lives on Eris.
Pass it on.
Knowing Google's lust for data collection, the Soviet Union is still alive and well inside the psyche of Sergey Brin....
You are correct. The 'planets' out that far are rather small. But both Pluto and Charon combined are still bigger than Eris, and any others yet to be discovered, in descending order of size. It was once thought that there could be massive planets lurking in the Ort Cloud, but Pluto/Charon and Eris may be the biggest (and only) ones there. It would be interesting to know how or what caused Pluto/Charon to break apart. There may be hundreds of smaller parts surrounding them both, as they orbit each other. Time will tell.
"If it doesn't work out the way you want it to, it will work out the way its supposed to be."
Thus raising the question, "What is the current definition?"
--AC
And for definition of the word "flat" that means "well, sort of spheroid", the world is indeed flat. This whole stupid squabble isn't about Pluto, its about the word "planet". You know what? I don't care what planet means. I don't care if you can consistently differentiate moons from planets or not. It will never, ever, ever impact my life. When my kid takes astronomy in school I will tell him "Son, here are the list of nine really big rocks which you need to learn to get to the next grade. Get started." Because that is all a planet is -- a big rock, which is special because we traditionally say it is. Whats the difference between a mountain and a hill? The mountain is labeled Mountain on the map, not hill -- its a big important rock, not like that everyday garden variety rock next door.
Astronomy, by the way, is a waste of classtime for science. Its studied purely for aesthetic reasons, always has been ("Ahh, the Heavens, they're so pretty the gods must have made them... and look, they obey convenient mathematical properties too!"), but you can find just as much aesthetic beauty in biology or chemistry or geology for that matter, and any one of these actually has practical applications. Not that any kid is likely to ever need to know the difference between metamorphic and igneous rock, but they will at some point come into physical contact with both of them, which is a heck of a lot more than you can say about Pluto/Eris. Astronomy as I was taught it was "Literature enjoyment of sci-fi novels", where they teach you to disregard everything you will ever learn about physics, math, and economics and pretend that you will, in your lifetime, see thriving and productive human colonies on celestial bodies which we know to be big, barren, worthless rocks.
Help poke pirates in the eyepatch, arr.
No. The period of revolution is independent of the mass of the moon and solely dependent on the mass of the planet and the distance from it.
n etary_motion
T^2 ~ r^3/M
http://en.wikipedia.org/wiki/Kepler's_laws_of_pla
Hubble can measure r. We can measure T by watching it over time. Hence, M.
"The joke is as old as the name. "
No, it's as old as the English Language.
When?
Real Soon!!!
th
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So to be a planet, you have to be the baddest badass in your orbit, and clear your path of all those other upstarts in your way? Pluto and Eris, being so far out, will probably never make it then since their orbits are so huge that some punk-ass twerp will always be able to settle in and make itself at home. It will take centuries until Pluto or Eris manages to swing around and pulverise the little creep. The distance between Pluto and Eris is also sufficient enough that they may never cross paths and enter a deathmatch. Things get weird once you get that far out from the star.
"I've got moons that are bigger than you."
What difference does it make whether there are nine things we call "planets," or eight, or ten, or a hundred, or a thousand? I suppose "planet" is a less special term if there's a lot of them, but we already know there are hundreds out there already; so what if there's a hundred in our solar system, or only fifty, or whatever. Seriously, what difference does it make to anything?
The physical and orbital characteristics of Pluto and Eris will remain the same regardless of whether we call them planets or minor planets or dwarf planets.
"Destroy science and religion. Science would re-emerge exactly the same; but not religion." - Penn Jillette, paraphrased
Notmysig
Pluto won't clear its orbital path in the lifetime of the sun for a few reasons.
The key reason it won't clear it's orbital path is because the term is undefined. Yes, I know about the paper from which the term was borrowed. I also know that the IAU didn't adopt that definition.
Nope, both you and the couple of people above you are wrong.
The orbit of the moon does depend on the mass of the moon.
The only time it's ignored is if the mass is negligible compared to the other body. So yah, the equations are right - but only in some cases (what do they say about a little knowledge being a dangerous thing?)
That may be the case here, I don't know. I didn't check for estimates of the mass of the moon of Eris.
But if the moon is large, then yes, you do have to take it's mass into account.
But it's not so hard to do so - just assume both the moon and the planet have equal densities, and you can solve it.
-Ariel
It's somewhat large? Check
It even has it's own moon? Check
So why is this not considered a planet? I never understood why we demoted Pluto.
If you really want to get picky on classification, we probably shouldn't put the outer planets in the same category with Earth. Earth & Pluto are more alike than Earth & Uranus. Earth & Pluto are both round, solid masses of various minerals. Uranus and the other outer planets are just enormous masses of gas with no solid surface and no rocky minerals.
Slow down, cowboy! It has been 4 hours since you last posted. You must wait another few hours.
"surely Eris would be considered the 10th planet."
;-)
No, no, no.... Mondas is the Solar Systems 10th Planet.
Mondas was Earth's twin planet, identical down to even the size and shapes of its continents. Millions of years ago, it was the tenth planet of the Solar System, until somehow it drifted out of its orbit and journeyed into deep space.
Ask any (classic) Dr. Who Fan...
http://en.wikipedia.org/wiki/Mondas_(Doctor_Who)
Stuart http://stuarthalliday.com/
"Hey, it's not your size that matters, it's how you orbit, baby."
Now we can send our intrepid space explorers there to protect the planet from King Zarkon.
This discovery changes nothing regarding Pluto's status. Mike "Pluto is dead" Brown is wrong in his non sequitur argument when he says "this is the last chance that Pluto had." Many in the astronomy community still consider Pluto a planet. There is hardly consensus otherwise, as Brown wants people to think. Eris being larger does nothing to negate the argument that Pluto is the solar system's ninth planet and Eris its tenth planet. Why the tenth planet cannot be larger than the ninth, in Brown's view, is beyond understanding. How can the status of another object, rather than its own characteristics, define what Pluto is? The truth is astronomers remain very divided on this issue, and the debate is not over.
I was at a classical music concert on campus when beforehand some young women were having an animated conversation about over-the-top-belt-wearing men and how ridiculous they looked. Normally one doesn't interrupt the fun conversation of strangers, but I couldn't stop myself then. At that time, Clyde Tombaugh was nearing age 100 and his picture would show up in Sky and Telescope. Planetary scientists talk about a North Equatorial Belt and a South Equatorial Belt (of Jupiter), I told them that Clyde Tombaugh, discoverer of Pluto, was definitely a North Equatorial Belt kind of guy.
"Oh yeah? Well at least I'm not made out of fart."
-
- - You can't take something off the Internet! That's like trying to take pee out of a swimming pool.
M is the mass of the primary, silly, not the moon. Duh.