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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.
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.
Some of us still consider that the world is flat.
Change can be hard.
The Kruger Dunning explains most post on
That Mondas is the 10th planet. Duh.
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.
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.
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.
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.
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.
This is the reason that people think Pluto should be a planet:
Did you learn it before you were ten years old? If yes, it can not ever change.
...but is it art?
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!
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?
Ceres was a "planet", or, at least, called one (1802), long before Tombaugh found Pluto (1930). So were some of the other asteroids. When they figured out it was just one instance of a large class of similar objects (asteroids), they changed its designation. Pluto/Charon (with the twins) has now been demonstrated as an instance of another large class of similar objects (Kuiper Belt Objects - KBO) that just happens to orbit noticeably closer than its siblings.
To the ancient Greeks a "planet" was any apparent celestial object, other than Earth's moon, that moved noticeably against the background stars. Working with just the unaided eye, Pluto doesn't count, because it cannot be seen. Working with telescopes, we've got effectively uncountable numbers of asteroids, KBOs, and galaxies that move against a galactic star field that is itself composed of relatively moving objects.
Between the time of Neptune's discovery and the asteroids' reclassification there were more than 10 planets, then back to 8. Pluto was prematurely added so we called it 9, then reclassified it, so now we're back to 8. Many objects have been mistakenly and/or prematurely classified (humans as an intelligent species, as opposed to the small number of intelligent individual humans, for example), then the classifications adjusted upon reexamination of the evidence or discovery of new evidence.
We throw labels at things. Sometimes they stick, sometimes they don't. Get over it.
"I've got moons that are bigger than you."