Two Planets Found Sharing One Orbit 175
dweezil-n0xad writes "Buried in the flood of data from the Kepler telescope is a planetary system unlike any seen before. Two of its apparent planets share the same orbit around their star. If the discovery is confirmed, it would bolster a theory that Earth once shared its orbit with a Mars-sized body that later crashed into it, resulting in the moon's formation."
Time for another IAU meeting (Score:5, Funny)
Quick, we need to redefine the meaning of "planet" yet again.
Re:Time for another IAU meeting (Score:5, Interesting)
Possibly. As neither has "cleared its neighbourhood" [wikipedia.org] of other masses in their neighborhood, they might be back to being called planetoids like Pluto. Both are to be considered "dwarf planets" until they collide and one becomes obviously dominant. There's already bits that cover things like this, but people are already arguing about the exampled in our own solar system. I be something like this would cause even more hub bub and another conference to further define the meaning of planet yet again.
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There can only be one!
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Moreover, at least outside exceptionally unlikely external forces, such a system is not stable, so the arrangement is temporary.
Re:Time for another IAU meeting (Score:5, Interesting)
Is an estimated minimum of 2 million more years not stable enough for you? With the two planets orbiting their star about every 10 earth days, that's over 70 million orbits, at minimum. What makes this an interesting find it that it IS unlikely, and it does NOT require external forces. Hence there's an article about it. :)
As referenced by TFA: http://en.wikipedia.org/wiki/Lagrange_point [wikipedia.org]
Unless you're claiming that nothing is stable because y'know, entropy, man!
Re:Time for another IAU meeting (Score:5, Funny)
Nothing is stable. All orbits change chaotically in the long term.
Corollary: There are no planets.
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Other fun facts about the universe: The universe contains no population, no money, and no sex*.
(*Actually there is quite a lot of this.)
Corollary: sex is entropy.
Corollary to the corollary: Slashdot is immune to entropy.
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Just because nobody's ever collected a Pu doesn't mean they don't exist.
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Even with the center of mass of each planet exactly in the L point of the other, then if the planet has a radius of 100km, parts of it will be 100kms away from the lagrange point --> inestability, whatever long it takes to become catastrophic.
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Ok, I was wrong.. [nasa.gov]
Anyway, I still find it counterintuitive for it to be stable; IANA (I am not an astronomer) but could someone point to some pages with the equations with the graviatory pull (potential) at L4/L5? Also, how big would be the "stable" area around L4 (in the Earth-Moon system).
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You don't need to be in Lagrange to be in a stable co-orbit. Look up the moons of Saturn. There are three pairs of moons that share the same orbit and only two of these are in a Lagrangian orbit. If this happens in our solar system, it is likely a relatively common occurrence in other solar systems.
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Ok, I was wrong [nasa.gov].
Anyway, I still find it counterintuitive... Are there somewhere the equations explaining gravitatory pull (potential) near L4? Also, can someone tell how big would be the "stable" area of L4 in, for example, the Earth-Moon system?
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http://en.wikipedia.org/wiki/Lagrangian_point [wikipedia.org] or more specifically,
http://en.wikipedia.org/wiki/Lagrangian_point#Stability [wikipedia.org]
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Even with the center of mass of each planet exactly in the L point of the other, then if the planet has a radius of 100km, parts of it will be 100kms away from the lagrange point --> inestability, whatever long it takes to become catastrophic.
Actually, two earth sized masses on opposing sides of the sun will stabilise each other.
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That's not what "clearing the neighborhood" is defined as. "Clearing the neighborhood" contains an exemption for other objects under the first object's gravitational influence.
If there are two objects in one orbit *and* the objects stay that way because of some complicated gravitational interaction, they are exempt from "clearing the neighborhood" and can still count as planets. In order to not count as planets you'd have to have two objects in the same orbit that just stay there because they happen to be
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Great, I foresee the birth of a new acronym, IANAAL - I am not an astronomical lawyer.
Re:Time for another IAU meeting (Score:5, Informative)
The definition that makes Pluto a dwarf planet specifically apples only to our solar system, and the part that calls for clearing the orbit was inserted in case a Kuiper belt object actually bigger than Mercury was found later, so the IAU would not have to debate the subject again, not as a straight-forward rule based on any physical fact. Incidentally, the belt is named after Kuiper because he was a. the third major working astronomer to propose such as zone, and b. the first to be fundamentally wrong about its nature, as he claimed such a belt could not still exist.
All the debate about how to define a an extra-solar planet will be driven by the very people who have totally screwed up any rational, scientific definitions when it comes to our own solar system. Expect a rule about how planets in the 'northern' part of the galaxy must have an eccentricity of less than 5.2%, and planets in the direction of Virgo are allowed 7.1%, but only if they move in square orbits on alternate St. Swithen'sdays.
Dwarf planet? (Score:2)
Both are to be considered "dwarf planets"
We prefer the term "little planets"... (you insensitive clod!)
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Also, those two extrasolar planets might very well be in a very strong gravitational interaction...
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Imagine what the last close flybys would have been like as an observer. Tidal forces ripping up the ground, seeing something massive in the sky getting larger and larger, then whoosh, and fading away. Awesome.
That'd probably get people's minds off of war and onto helping one another pretty quick.
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Quick, we need to redefine the meaning of "planet" yet again.
Yeah... because it's been changed so many times, right? And for no good reason to boot, right?
Truth is, the term "planet" has only really been defined once, a few years ago. before that, we had an intuitive idea of what a "planet" was; we included Pluto, as it appeared to be a comparatively unique object, but then we found that Pluto isn't unique and that there is no reason to believe that we wouldn't have millions (at least!) of planets, since there'll be that many objects that all share Pluto's characteri
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Well, it pointless to start or maintain an argument because of this discover. what they are observing is the Death star beta production facility. It just took a long time for the light to eventually reach us. But then again, it all happened A long time ago in a galaxy far, far away.
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as long as you don't define "planets" as "girls" and "orbit" as "cup".
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Does the IAU have jurisdiction over extra-solar planets?
It would be interesting to see them tell some advanced alien race 'sorry the world you live on is not a planet'
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In my best Jean Luc Picard: There....are...nine...planets!
You can't explain that! (Score:5, Funny)
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Theia goes in, Moon comes out.
You can't explain that!
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At least he might believe in the hot place to which his credibility hand-basket may be headed... B^>
Rgds
Damon
Oblig. Star Wars reference (Score:2)
I always assumed that Dantooine and Tatooine were twin planets like this. Or did that mean something else?
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I don't think they're even supposed to be in the same solar system.
The classic twin planet arrangement is two planets orbiting each other though. Like the Earth and moon.
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Adding to catmistake's reply: we say that Jupiter orbits the Sun, but the center of gravity of those two bodies is outside the sun In any event when A orbits B it is perfectly okay to say that B orbits A. Its the same thing.
Also the moon is a moon because we call it the moon. The laws of gravity don't care what we call it just as they didn't care about me when I fell off my bike.
First? (Score:5, Informative)
It's not clear that this is anything new. A number of astronomers have suggested that we should treat the Earth/Luna and Pluto/Charon pairs as "double planets" sharing an orbit. And there's a pair of Saturn's moons that share an orbit. Of course, whether these are counterexamples depends on the picky, legalistic details of how you define the term "planet", which we've discussed to death here on /. already. Fun as such pseudo-arguments may be, the fact is that they're not terribly significant.
Thus, for the Pluto/Charon pair, reclassifying Pluto as a "dwarf planet" make it especially an edge case, since it still includes the term "planet" in its classification. But they're both large, spherical bodies in a single orbit around the sun, while also orbiting each other.
The Earth/Luna pair is a bit of a mathematical curiosity. One of the arguments supporting calling our moon a "planet" orbiting the sun is that its orbit is everywhere convex with respect to the sun. You'd expect a "moon" to have a much more wiggly orbit, parts of which are curved away from the sun, and this is true of the other objects in the solar system that we call moons. OTOH, the barycenter of the Earth/Luna pair is (slightly) inside the Earth, which can be used with some definitions to say that it's really a satellite of the Earth.
And, of course, Saturn's two moons in a single orbit can be disqualified because they're obviously not "planets". They're not even big enough to be spheroidal, which is required by most definitions of a planet.
But the fact remains that our solar system contains at least three example of paired bodies sharing an orbit about their primary, and periodically exchanging the lead position. The mechanics of such orbits have been long understood, and astrophysicists can tell you when such orbits are stable. So while this may be "news" in the sense that it's about such orbits around another star, it's hardly news in the astrophysics sense.
What'll be interesting news is the discovery of three astronomical bodies in a "Scottish reel" orbit, which was proved possible several years ago, but to my knowledge hasn't actually been observed yet. Possible places to find them are in the asteroid belt, in Jupiter's "Trojan" asteroid clumps, and in the Kuiper Belt.
Re:First? (Score:5, Informative)
What'll be interesting news is the discovery of three astronomical bodies in a "Scottish reel" orbit, which was proved possible several years ago, but to my knowledge hasn't actually been observed yet. Possible places to find them are in the asteroid belt, in Jupiter's "Trojan" asteroid clumps, and in the Kuiper Belt.
I googled "scottish reel orbit" and of course the first result was your own post. However, I did come across this, for those who are interested: http://faculty.ifmo.ru/butikov/Projects/Collection3.html [faculty.ifmo.ru]
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That page doesn't account for the stress on objects caused by the changes in gravitational force. There are some very drastic changes in speed in some of those.
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The fish one made me laugh. It is named "5 on...". Not cool how it chops off the names...
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I note that your post is the first I find to be on topic (and not +'Funny')
TFA does not really say much. In addition, when I follow suggested links in its hosting webpage, "Read more:", as they put it, I am informed that I have not clearance enough, something that can be altered if I will part with my personal information and/or credit card number.
And all that just to read insufficiently technical articles like this? Are the restricted articles more technical? I am puzzled- Is this a lifestyle tabloid?
Note that these planets do not orbit each other (Score:3)
These planets are at the stable lagrange points, not in orbit with each other.
Which, by the way, is perfectly fine with regards to the IAU's definition. These planets have cleared their orbit nicely, and are gravitationally bound to each other.
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if the Sun disappeared, the Moon would still orbit the Earth.
I am not so sure to be honest. Its been a while since I had to do the calculations. I reckon it would be touch and go. There should be a way to compare the affect of the solar and terrestrial gravitational fields on the moon.
This is probably a horseshoe orbit pair (Score:3)
Two planets orbiting the same star is arguably only possible with horseshoe orbits. If two objects are of similar size so on cannot say one orbits the other, it is described a a double body rather than primary and satellite.
A Lagrangian moon will likely develop into a horseshoe orbit over time.
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Saturn's two moons in a single orbit
The moons distance from the Earth increases as angular momentum is transferred by tidal action. Makes me wonder if Earth and Luna will eventually co-orbit in that way. Doesn't sound very safe for us, but certainly spectacular.
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So while this may be "news" in the sense that it's about such orbits around another star, it's hardly news in the astrophysics sense.
It's news in the sense that it provides more information about the dynamics of planetary formation, at least amongst hot Jupiters. While we know that the orbital dynamics of these bodies creates a stable situation, we did not know that they could actually form this way--the dynamics of early planetary formation is still much debated. There are a lot of things that happen, the initial conditions are not well-understood, the collision dynamics depend on the properties of the colliding bodies, etc. Ergo, th
Keplerian Occultations (Score:4, Insightful)
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The distance from the star doesn't matter much for occultation methods. The difference between the Earth orbital radius and the Jupiter orbital radius from tens or hundreds of light years is negligible. The place where the radius does make a difference is in the time to repeat an observation. To get the orbital period of a planet in an Earthlike orbit will take around a year, while a jupiterlike orbit would require 16 years. The "wobble" method that found the first planets is the one that is really sens
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The distance between the planet and the star matters very much for the occultation method. That's because planets that are far away from their stars don't orbit very often. We are exceptionally unlikely to spot a planet that only orbits once a century with a telescope that has only been looking for a year.
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Imagine the sun (1.39E6 km) is as big as a square on a sheet of graph paper (1/4 inch). The Earth would be 100 squares away (about 2 1/4 sheets taped together the long way). The Earth is about 1/100th the size of the sun, so it would be much smaller than a period. What matters for Kepler is the angular size of the star. That is because on the scale with graph paper, Kepler would be 6,770 MILES away. Basically we could see any planets whose orbit takes them into that one square line of graph paper poin
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Kepler was specifically designed to find planets of an interesting size (like Earth, but it can certainly detect larger ones) in interesting orbits (like Earth's, but it can certainly detect ones closer in). We have other methods to identify giant planets further out.
two planets one orbit (Score:5, Funny)
Oh, sorry, typed it wrong...
Who are we to define "orbit"? (Score:2)
It's not a real planet . . . . until . . . (Score:3, Interesting)
Captain Kirk beams down there, takes his shirt off, and gets the chick. Wait, two planets? Wait a second, we'll have to fly in a second, evil, Captain Kirk from a parallel universe. And how about a Spock with a beard? Does Ryanair fly there? Can we get a discount rate for two? Well, knowing them, they'll charge an extra exorbitant fee for Spock's beard. And the plane won't even land in the parallel universe, but in another universe, "Really close by!"
"typical" solar system may be defined by Kepler (Score:2)
And I Hear the RIAA (Score:2)
...is filing a few billion John Doe lawsuits against "Any and all current or potential occupants of said potentially planetary bodies..." for sharing an orbit.
Sharing is bad
subject (Score:2)
Planet...or space station?
DUNH DUNH DUNH!
Disc of Material (Score:2)
In theory, matter in a disc of material around a newborn star could coalesce into so-called "co-orbiting" planets, but no one had spotted evidence of this before.
Off course not. Even star turtles like a little privacy.
Science-Fiction does it again! (Score:2)
Doppelgänger [wikipedia.org] (Journey To The Far Side Of The Sun).
Spot any rings yet? (Score:2)
No, not belts. You know. Like, rings, dude. You know that's what Kepler's *really* for, right?
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That would be in the L3 point, and that one is highly unstable, and a planet in L3 would be knocked out of it whenever Jupiter or Mars is close by.
L4 and L5 is much more likely, but not for a duplicate Earth, as we would be able to see it from here.
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That there's a duplicate Earth on the exact opposite side of the Sun!
First rule in government spending: why build one when you can have two at twice the price?
All ready been proven (by movies at least) Doppelgänger [wikipedia.org]
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It's "already" (déjà), not "all ready" (tout est prêt)...
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Watched the movie, wasn't really impressed.
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You mean the one on the dark side of the Sun?
Re:And bolster my theory (Score:4, Funny)
Check Wikipedia.
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Vote.
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Or you could watch the 1969 movie Doppleganger which covers just this.
OR you could read the Wikipedia entry on the movie Doppleganger [wikipedia.org] and be even betterER!
Re:And bolster my theory (Score:4, Informative)
That there's a duplicate Earth on the exact opposite side of the Sun!
OK, just for the fun of it: what would be the most efficient method to check this hypothesis?
That would be STEREO [nasa.gov].
Gravity of an Earth-size body at L3 (Score:5, Informative)
That there's a duplicate Earth on the exact opposite side of the Sun!
OK, just for the fun of it: what would be the most efficient method to check this hypothesis?
By checking how its gravity would effect other planets in the same star system. For background: Counter-Earth on Wikipedia [wikipedia.org], Lagrangian point L3 on Wikipedia [wikipedia.org], and Counter-Earth on TV Tropes [tvtropes.org]. Executive summary: We don't have one, and we know this because if we did, we'd be able to detect its pull. Furthermore, such an orbit would be unstable.
Re:Gravity of an Earth-size body at L3 (Score:4, Funny)
Checking Wiki worked! :)
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Especially considering the number of satellites accumulating at L4 and L5, one or more would have a line of sight to both Earth and Earth's L3. If we ever get around to doing some Manned Mars missions, we'll probably have some commo birds sitting in L4 and L5 as well.
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That there's a duplicate Earth on the exact opposite side of the Sun!
OK, just for the fun of it: what would be the most efficient method to check this hypothesis?
Um, ask someone on /. ? (but not the guy who keeps posting 'First Planet!')
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Re:And bolster my theory (Score:5, Funny)
.htraE ylno eht si sihT .tuoba gniklat er`uoy tahw wonk t'nod I .uoy rof taht dexiF
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Simple: Launch a nuclear missile in the same orbit as Earth but in the opposite direction. Wait six months.
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You would need 60km/s delta-v. Currently infeasible.
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Strictly speaking, the planets would not actually share a common orbit. At least, in order for the orbit to be stable, that is. What you would actually have are two counter-rotating elliptical orbits in precise resonance with one another. To picture this, imagine a two component Venn Diagram using ellipses instead of circles. The Sun would be in the precise center, with the outer edges of the ellipses being the planetary orbits.
This is the ONLY way that we could have an orbiting "companion" planet that
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Efficiency: check Wikipedia.
Effectiveness: Look at the calculations that were done hundreds of year ago, disproving this theory. The outer planets were found because people simply calculated the orbits of the other planets, saw that they were off and then went to calculate where the influence should sit. Eh, presto.
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It would be even cooler to find their still-functioning planet moving drives because if the things weren't still working the planet would have drifted out of the unstable L3 point already.
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Only if it is perfectly balanced, but in the real world nothing stays in that state for ever.
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Why not just do a ringworld?
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Because we don't know how to make Scrith, and the concept terrifies the puppeteers so they won't save us from the Kzinti.
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or even a Dyson Sphere variant at approximately 1AU?
I am quite attracted to this planet. My preference would be to build the Dyson Sphere around a different star. I am sure there are plenty of red dwarf stars out there with only gas giant planets for building material.
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how is this amazing. there are an infinite amount of things in the skies... I wouldn't be surprised to see a new Galaxy that had an outline shaped like a Penis
I think they've already found one in the Porn Cluster ... I think it's called the Sheen Galaxy.
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Yes. Please say nothing more of Gor, thank you.
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No, but I've had sex with plenty of them. Does that count?
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There is a ridiculously enormous amount of data. Numerous cameras, totaling to almost 100Mpixels 'blinking' every 6 seconds. Assuming a minimum of 4 bits per pixel, that would be at least 720 Gb every 24h, that somehow have to be transmitted to a station on Earth from wherever the hell Kepler is. And nor that traffic includes flight and error control, neither the maintenance and diagnostics on the on-board computer is included in the former calculation. Plus, for some reason, there is not enough bandwidth t
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1. read slashdot ...
2. attempt humor
3.
4. PROFIT!!!
Two planets cohabiting an orbit; what could be funny or profitable about that?
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Isn't an orbit determined by the center of the rotation? The Earth is in orbit around the Sun and the moon is in orbit around the Earth.
Why isn't moon capitalized? Because it's not a planet! Now go to your room!
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The Moon is capitalized because its a proper noun in this usage. In general usage we call the moon that is orbiting the Earth simply "the Moon". And since there is only one moon orbiting the Earth and it is referred to as the Moon, it is correct to capitalize it.
In the solar system there are many moons but there is only one Moon.