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First Exoplanet Discovered Orbiting Two Stars
astroengine writes "For the first time, astronomers have discovered an exoplanet orbiting binary stars. Kepler-16b, a Saturn-sized world approximately 200 light-years away, orbits Kepler-16, two stars locked in a mutual dance. Although other exoplanets are known to exist in binary systems, they have only been known to be orbiting one star of the binary pair; Kepler-16b orbits both. No doubt Kepler-16b will excite memories of Tatooine, Luke Skywalker's homeworld, but the double sunset is where the similarities end. Kepler-16b would be anything but a desert world; it is the approximate size of Saturn, it is extremely cold, and its average density is that of water."
The first planet orbiting two stars?
The exoplanet part being redundant.
Wow, sent an e-mail as suggested when clicking on "use classic" banner, and got a fast response that addressed my msg
A desert doesn't have to be hot and covered in sand.
"I use a Mac because I'm just better than you are."
Tatooine? Would that thing not be much more like Solaris (the planet from the novel, not the OS), especially since it's density is that of water?
No, but they built planets there.
The Tao of math: The numbers you can count are not the real numbers.
How do they calculate the density of these things? I get that they can detect the mass from the wobble of the star. How do they calculate the volume?
Give me Classic Slashdot or give me death!
I think they're using the same AI that writes up spam comments to do their articles.
"When information is power, privacy is freedom" - Jah-Wren Ryel
No. This planet is not like Tatooine. It is likely to be very cold because both of the two stars are in fact quite dim. Much closer to Hoth than Tatooine. See Phil Plait's description here where he discusses how you can estimate the planet's probable temperature- http://blogs.discovermagazine.com/badastronomy/2011/09/15/astronomers-discover-a-wretched-hive-of-scum-and-villainy/.
As the stars slipped toward the horizon, they would change places in the sky, like partners in a square dance.
and
You would not need to be Luke Skywalker visiting his home planet of Tatooine in the movie "Star Wars" to watch the twin sunset.
...poor science reporting, but apt science reporting summarizing.
0 = 1 + e^(Alt something)
So, can anybody who understand this explain a little more.
Is the orbit of the planet around both stars, making it like the orbit is eccentric around some center of mass common to the two stars?
If it's that, then I think I get this. If it's anything beyond that, then I'm afraid my meager understanding of Kepplers laws falls apart.
Most importantly, I love this part:
the stuff we've just discovered will go away for the next 30+ years. That's really quite cool, since the window in which we could have identified this and worked it out is likely fairly short ever since we identified the very first exoplanets back in the 90s or so.
Lost at C:>. Found at C.
Fantastic, now all we need is a Placet (from Fredric Brown's Placet is a crazy place).
Is sol our sun?
This planet had an orbit of 229 days. Kepler ideally desires three transits with two equal intervals to call it planet candidate. Kepler's observing duration is approaching the length where it could start detecting Earth-year planets now. The alternative experiments havent had enough sensitivity or duration to detect many Earth-year planets. Earth-year planets are likely to be in the habitable zone of G-type stars like the Sun.
I thought the next big Kepler data dump would be September 23 2011, after many of the preliminary papers had been published.
I *might* be able to get excited about these sorts of discoveries if once.... just once... they found a rocky planet in the habitable zone of a star having between roughly .75g and 2g... and I'd especially get excited if they could determine that it has a breathable atmosphere and presence of water.
We already know that we can detect gas giants around other stars. We've been doing it for years now and considering that binary stars are not that uncommon in our galaxy, it should come as no surprise that there might be planets around some of them.
Why is this news?
File under 'M' for 'Manic ranting'
Looks like the human race is run.
This is when things will get really exciting. Even though I have become jaded about space travel over the last three decades, I am still excited about the prospect of being able to observe the galaxy. Once we've cataloged a few hundred planets very similar to our own, we will finally get some good statastical support around how common life is in the universe. The first step is obviously finding them. The next is analyzing them.
If we can keep our society from falling apart and at least somewhat focused on science, we will see some pretty amazing discoveries this century.
See my journal for slashdot ID's by year. Mine created in 2005. http://slashdot.org/journal/289875/slashdot-ids-by-year
And not just one of them. Kepler has previously found 5 Earth-sized planets, in the habitable zones around their stars. And quite a few that are either Earth sized, or in the habitable zone, but not both. Including things like super-Earth sized ones in the habitable zone. :) http://www.nasa.gov/mission_pages/kepler/news/kepler_data_release.html
The findings increase the number of planet candidates identified by Kepler to-date to 1,235. Of these, 68 are approximately Earth-size; 288 are super-Earth-size; 662 are Neptune-size; 165 are the size of Jupiter and 19 are larger than Jupiter. Of the 54 new planet candidates found in the habitable zone, five are near Earth-sized. The remaining 49 habitable zone candidates range from super-Earth size -- up to twice the size of Earth -- to larger than Jupiter. The findings are based on the results of observations conducted May 12 to Sept. 17, 2009 of more than 156,000 stars in Kepler’s field of view, which covers approximately 1/400 of the sky.
In this case they could cheat -- the two stars are orbitting each other fairly rapidly compared to the planets orbital period. They could see them alternately passing behind the planet. You would be able to see the phase shift in the light dip and from that you can deduce the orbital speed of the planet. Other clues from ground based observation would confirm the planet and allow its mass to be determined.
It was my understanding that a planet made entirely of water would not have enough mass to hold together, and would eventually disapate. Thus... wouldn't a planet made of something equal to the density of water also have trouble forming and maintaining coherence?
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That is incorrect. The idea that all the objects orbit the barycenter is valid for objects within a few orders of magnitude, which pull on each other. The planet's mass really is too little to have any nonnegligible effect on the stars (which do pull on each other). Thus the stars' barycenter is not wobbling to meet up with the planet.
Three-body problems are not intuitive, especially when you have objects of vastly different mass.
It is dangerous to be right when the government is wrong.
Just outside Mexico City we have "Desierto de los Leones" (the lions' desert). It is a beautiful forest with a 400 year old convent in it.
Why?
Because it used to belong to the "de León" family, and it was far enough from the city that it became a perfect spiritual retirement place - A desert.
Thats kind of why the Kepler Consortium suggests hundreds of "candidate" planets to be verfied by further study. Its estimated there may be alternative hypotheses explaining the light curves of 5% - 20% of the candidates.
Poincare would be so excited about this... Poincare and the three-body problem
I also wanted to bring up the Pluto - Charon system. You are correct regarding the orbits of Nix, Hydra, and apparently the newly-discovered Plutean moon. Their velocity vectors seem to be consistent in magnitude, and perpendicular to the barycenter.
However, the case of a planet orbiting two stars, assuming that the stars are within a few orders of magnitude of each other but that the planet's mass is quiet a few magnitudes less then the star's mass (Earth: 10^24, Sun/Sol: 10^30), will see it's velocity vector change magnitude often and it will rarely be perpendicular to the barycenter.
It is dangerous to be right when the government is wrong.
I should also mention the possibility that the planet is not orbiting in the same plane as the stars! Though that is probably not a possibility here, considering how we detect dual-star systems and how Kepler detects planets.
It is dangerous to be right when the government is wrong.
...According to the BBC this morning Kepler-16 is only 20 LY away... of course, the BBC have it completely wrong; from the NASA initial press release:
"The distance from Kepler-16 to Earth has not been measured, but is probably about 200 light years, judging from the apparent brightness of star A and theoretical models of stellar structure that give a crude estimate of its intrinsic luminosity."
http://kepler.nasa.gov/Mission/discoveries/kepler16b/
Operation Guillotine is in effect.
To calculate density they need both mass and volume. Mass is in principle calculated by the wobble of the source star, and assumes that you have an accurate measure of it's mass. However circling a binary, the wobble is that of the pair. The uncertainty of this is substantial.
To calculate the volume, you need the diameter. This would require having a reasonable curve of light drop as the disk of the planet transits one of the stars. Is Kepler sensitive enough to pick out the effect of the shadow of a single planet on the solar disk? E.g. if the planet is 100,000 km in diameter, and moves at 10 km/second then time from first contact to occlusion would be 10000 seconds. If the star itself is 1,000,000 km in diameter then the planet's disk represents 1% of the star's area, and that will be the decrease in illumination in transit. However to guage the time of first contact to occulsion, you are working with small chords overlapping. Which means that you need to record variations in output of something like 3 orders of magnitude smaller.
The orbital speed is also subject to error. A far out planet will not be observed for even a single orbit. So you have to deduce speed from the speed change of the orbited star. Is dopler that good.
A 10% error in diameter means a 30% error in volume. And I'm skeptical of even getting within 10%.
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