2 Planets found in same orbit

[Tasha]

http://www.newscientist.com/article/dn20160-two-planets-found-sharing-one-orbit.html

 

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.

The two planets are part of a four-planet system dubbed KOI-730. They circle their sun-like parent star every 9.8 days at exactly the same orbital distance, one permanently about 60 degrees ahead of the other. In the night sky of one planet, the other world must appear as a constant, blazing light, never fading or brightening.

Gravitational "sweet spots" make this possible. When one body (such as a planet) orbits a much more massive body (a star), there are two Lagrange points along the planet's orbit where a third body can orbit stably. These lie 60 degrees ahead of and 60 degrees behind the smaller object. For example, groups of asteroids called Trojans lie at these points along Jupiter's orbit.

 

 

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. "Systems like this are not common, as this is the only one we have seen," says Jack Lissauer of NASA's Ames Research Center in Mountain View, California. Lissauer and colleagues describe the KOI-730 system in a paper submitted to the Astrophysical Journal (arxiv.org/abs/1102.0543).

 

 

Richard Gott and Edward Belbruno at Princeton University say we may even have evidence of the phenomenon in our own cosmic backyard. The moon is thought to have formed about 50 million years after the birth of the solar system, from the debris of a collision between a Mars-sized body and Earth. Simulations suggest the impactor, dubbed Theia, must have come in at a low speed. According to Gott and Belbruno, this could only have happened if Theia had originated in a leading or trailing Lagrange point along Earth's orbit. The new finds "show the kind of thing we imagined can happen", Gott says.

 

 

Will KOI-730's co-orbiting planets collide to form a moon someday? "That would be spectacular," says Gott. That may be so, but simulations by Bob Vanderbei at Princeton suggest the planets will continue to orbit in lockstep with each other for the next 2.22 million years at least.

 

 

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Reminds me of a Klemperer rosette though with less planets. 2.2m years seems to be long enough if you want to have a colony there...

[tkdguy]

Re: 2 Planets found in same orbit

 

I can create a Pulp science fiction campaign based on this info. Thanks for sharing.

[Steve Long]

Re: 2 Planets found in same orbit

 

Every day seems to bring more cool info for the new Star Hero.

[BobGreenwade]

Re: 2 Planets found in same orbit

 

I would be not at all surprised if we eventually discovered a system somewhere in the Milky Way with two planets sharing an orbit in the habitable zone (and both are indeed habitable).

[Cancer]

Re: 2 Planets found in same orbit

 

I'm trying to wade my way through the preprint from which this information is taken, but it's a back-breaking 106 pages of ApJ-ese. This will take a while.

 

EDIT: Not as bad as I feared. Of that 106 pages, 36 are text. Two are blank, and the rest are big tables of candidates and "expected false positives" (that is, things that pass their initial selection criteria but when better criteria are used they probably aren't planets).

[Shadow Hawk]

Re: 2 Planets found in same orbit

 

I would be not at all surprised if we eventually discovered a system somewhere in the Milky Way with two planets sharing an orbit in the habitable zone (and both are indeed habitable).

 

Theoretically... (correct me if I'm wrong) you could have three planets sharing a orbit, with two habitable. I'm thinking gas giant with habitable planets in the L4 and L5 spot.

And... A habitable moon.

All with intelligent races, all hating each others guts.

You mission, should you choose to accept it, is to devise a treaty between the three that is fair and acceptable.

This post will self destruct in 3 seconds.

[Cancer]

Re: 2 Planets found in same orbit

 

OK, so this system (KOI-730) is a 4-planet system. The star has a Teff of 5600 K, that's 180 K cooler than the Sun. Well within the sunlike regime.

 

• Planet -04 is the closest to the star. It is 0.076 AU out, and the planet radius is 1.8 times that of Earth.
  
• Planets -02 and -03 are the "orbit sharing" ones. 0.092 AU out. The planet radii are 2.3 and 2.5 Earth radii respectively.
  
• Planet -01 is 0.12 AU out, and a radius 3.1 times Earth's.
  

For reference, Mercury is 0.39 AU away from the Sun. The estimated planet surface temperatures range from 746 to 937 K. For comparison, the surface of Venus is at 735 K due to the runaway greenhouse effect of all its CO2 being in the atmosphere (such an effect is possible on these planets, but the temperatures estimated don't include anything like that).

 

More generally ...

There are 1235 planetary candidates with transit like signatures detected in this period. These are associated with 997 host stars. Distributions of the characteristics of the planetary candidates are separated into five class-sizes; 68 candidates of approximately Earth-size (Rp < 1.25 Rø), 288 super-Earth size (1.25 Rø < Rp < 2 Rø), 662 Neptune-size (2 Rø, < Rp < 6 Rø), 165 Jupiter-size (6 Rø < Rp < 15 Rø), and 19 up to twice the size of Jupiter (15 Rø < Rp < 22 Rø).

(Rp stands for "planet radius". I've used "Rø" to mean "Earth radii"; the Earth symbol used by astronomers is not available, AFAIK, in any of the ISO Latin character code sets.)

 

[ATTACH=CONFIG]38064[/ATTACH]

 

That's a histogram of the planet radii of the 1200+ candidates from the first four months of science observations by Kepler. (Those are the same information in the two figures, one's on a log scale, the other not.) The upshot is that smaller planets ARE more common than larger ones, at least in the orbital range sampled in this list. (To have made this table, a planet has to have at least two transits in that four month time period. Note that of the planets in our Solar System, only Mercury could possibly have appeared in this table; all the others cannot have transited more than once even under ideal circumstances, and you'd've had to be lucky to get two from Mercury in that period.) There's a cutoff at small radii because the telescope can't detect planets if they are too small. There's a cutoff at big radii because once it gets too big it's probably not a planet (it's a star). The authors have put in a smooth curve, where the number of planets scales the inverse square of the planet radius (e.g., planets half an earth radius are nine times as common as planets 1.5 earth radius).

 

Now, the four-month timespan limits these data to planets that are pretty close in (Kepler's 3rd Law links orbit size to orbit period very tightly). But clearly: there ARE lots of Earth-class planets out there. They are just hard to see under most circumstances, the Kepler mission for the first time gives us an estimate on that population.

[Tom Carman]

Re: 2 Planets found in same orbit

 

I would be not at all surprised if we eventually discovered a system somewhere in the Milky Way with two planets sharing an orbit in the habitable zone (and both are indeed habitable).

 

With a bit of planetary engineering, you could have 6 planets sharing an orbit 60 degrees apart. Each world would in the L3, L4 and L5 points of 3 of the others.

[austenandrews]

Re: 2 Planets found in same orbit

 

What does this do to the "clears its orbit" component of the definition of "planet?"

[Cancer]

Re: 2 Planets found in same orbit

 

What does this do to the "clears its orbit" component of the definition of "planet?"

Dunno yet.

 

IMO, it vindicates my opinion about that entire issue.

[Lord Liaden]

Re: 2 Planets found in same orbit

 

With a bit of planetary engineering' date=' you could have 6 planets sharing an orbit 60 degrees apart. Each world would in the L3, L4 and L5 points of 3 of the others.[/quote']

 

That would also allow for the classic "counter-earth" concept, of two planets of roughly equal mass sharing the same stable orbit 180 degrees apart, on opposite sides of their sun and so never seeing each other.

[Starcloud]

Re: 2 Planets found in same orbit

 

Two planets 180 degrees apart doesn't work; the gravitational influence of the planets being opposite each other is not sufficient to keep the orbit stable, if I remember correctly.

[Badger]

Re: 2 Planets found in same orbit

 

I can create a Pulp science fiction campaign based on this info. Thanks for sharing.

 

Just please dont name after a former VP of the US (minus the silent E at the end)

[Badger]

Re: 2 Planets found in same orbit

 

Theoretically... (correct me if I'm wrong) you could have three planets sharing a orbit, with two habitable. I'm thinking gas giant with habitable planets in the L4 and L5 spot.

And... A habitable moon.

All with intelligent races, all hating each others guts.

You mission, should you choose to accept it, is to devise a treaty between the three that is fair and acceptable.

This post will self destruct in 3 seconds.

 

Well, first I'll need Cpt. Kirk and a hot alien chick.....

[BobGreenwade]

Re: 2 Planets found in same orbit

 

Just please dont name after a former VP of the US (minus the silent E at the end)

What would be wrong with calling it Quayl?

[Lawnmower Boy]

Re: 2 Planets found in same orbit

 

What would be wrong with calling it Quayl?

 

Well, duh. Obviously because of the last pulp Sci-Fi series with that title from the 70s and 80s. You know. The one with where the rampant foot fetishism took over from the adventure.

 

"Girl, your decadent steel cities of Earth have never seen heels this high. But on the Counter-Earth, you will walk the streets of seven-gated Thebos with your feet clad thus! Your primal nature will know that it is only when your toes are strapped so purely, so sweetly, that you will give true pleasure to the manly man warriors of Quayl!"

[tkdguy]

Re: 2 Planets found in same orbit

 

tkdguy looks at his Chronicles of Quayl manuscript and almost tears it up in disgust... almost. At the last moment, he has a flash of inspiration and changes it to Chronicles of Cheny.

 

Yup, that's the ticket.

[Badger]

Re: 2 Planets found in same orbit

 

No Love for the The Chronicles of Mondal I see

[Tasha]

Re: 2 Planets found in same orbit

 

No Love for the The Chronicles of Mondal I see

 

a pleasant enough read, but kind of dull and uninteresting. Though the test drive of the tank was kind of funny.

[Old Man]

Re: 2 Planets found in same orbit

 

That would also allow for the classic "counter-earth" concept' date=' of two planets of roughly equal mass sharing the same stable orbit 180 degrees apart, on opposite sides of their sun and so never seeing each other.[/quote']

 

Actually, has anyone bothered to check if there's another Earth on the other side of the sun from us?

[Tasha]

Re: 2 Planets found in same orbit

 

Actually' date=' has anyone bothered to check if there's another Earth on the other side of the sun from us?[/quote']

 

Given the flight paths of the many probes we have sent to the outer reaches of the solar system. One would have thought that a 2nd body in any orbit would have been noticed by now.

 

[tinfoilcap]or the Men in Black have been supressing information about it. Like they have the UFO's, Face on Mars, Lizard People living among us, and all of the other weird Conspiracies. [/tinfoilcap]

[Xavier Onassiss]

Re: 2 Planets found in same orbit

 

Actually' date=' has anyone bothered to check if there's another Earth on the other side of the sun from us?[/quote']

 

IANAOM (I Am Not An Orbital Mechanic), but I think another Earth-size object opposite ours would have a noticeable influence on the orbit of Venus, and possibly Mercury and Mars.

[Cancer]

Re: 2 Planets found in same orbit

 

It would, and Tasha is also correct: it would have been seen by now from any of a number of different spacecraft.

[Tasha]

Re: 2 Planets found in same orbit

 

IANAOM (I Am Not An Orbital Mechanic)' date=' but I think another Earth-size object opposite ours would have a noticeable influence on the orbit of Venus, and possibly Mercury and Mars.[/quote']

 

Not to mention all of the Near earth orbiting bodies, and other small bodies floating around here in the solar system.

[Old Man]

Re: 2 Planets found in same orbit

 

So basically what you guys are saying is, their cloaking device is on, and they have antigravity tech.