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New Alpha Centauri planets quest, thanks to TPS !
vikingmars
post May 15 2012, 12:37 PM
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In 2009, the Planetary Society (TPS) made a grant to Yale University astronomer Debra Fischer. With those funds, Debra and her team developed the FINDS Exo-Earths project to record the light from distant stars with increased precision in the search for Earth-like planets, which they then installed on the telescope at Lick Observatory in California. "I'm betting that there are planets like Earth or Mars or Venus around either or both of the stars of Alpha Centauri, and the only question is whether we'll be able to detect them," said Debra Fischer in 2009.
Well... If the astronomers succeed in detecting small planets orbiting around "Alpha-A" and/or "Alpha-B" stars, no doubt that it will be a scientific bombshell -- and also, it will raise the question of how we might someday send a probe to get a closer look.

Now, Debra Fischer and her team are focusing again on Earth’s nearest neighboring star system, Alpha Centauri, to look for Earth-like planets. And TPS wants everyone interested by this great quest to join the team. The telescope will be in the southern hemisphere to see Alpha Centauri, so Debra and her team need to rent time at the Cerro Tololo Inter-American Observatory in Chile. They need TPS to sponsor at least 20 nights of observation time.
And because Alpha Centauri B shares the system with Alpha Centauri A, we can also begin to understand the question : how do planets develop in a true binary system, pulled by two gravitational bodies?

As a TPS member, but also belonging to Societe Astronomique in France, I'm really thrilled by this new research project which fits exactly within TPS's goals which are: "To inspire and involve the world's public in space exploration through advocacy, projects, and education".
Many thanks to the TPS's team for this idea of great science value smile.gif
Now you can, please like me, follow the link and make a donation :
http://support.planetary.org/site/Donation...&df_id=1640

Also, I put herebelow some interesting links and science articles abour the "A-B" system, you may like to read to better understand what it is all about.
Enjoy ! smile.gif
http://www.planetary.org/explore/projects/finds/
http://www.planetary.org/blogs/bruce-betts...ound-alpha.html

Attached File  Davis_1b_xxx.pdf ( 585.56K ) Number of downloads: 156
("One planet can be reliably detected after the first 2 years of observations, and 3 planets can be detected within 4.7 years." !!!)
Attached File  AlphaCenApJPaper_2__Part1.pdf ( 291.76K ) Number of downloads: 184
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vikingmars
post May 15 2012, 12:39 PM
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(Another document...)
Attached File  AlphaCenApJPaper_2__Part2.pdf ( 894.7K ) Number of downloads: 284
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vikingmars
post May 15 2012, 12:40 PM
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(...idem...)
Attached File  AlphaCenB_1_xxx.pdf ( 359.86K ) Number of downloads: 175
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vikingmars
post May 15 2012, 01:05 PM
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(...and the last document)
Attached File  AlphaCen_1_xxx.pdf ( 995.08K ) Number of downloads: 264

Enjoy smile.gif smile.gif smile.gif
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IM4
post May 16 2012, 03:42 PM
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QUOTE (vikingmars @ May 15 2012, 12:37 PM) *
"One planet can be reliably detected after the first 2 years of observations, and 3 planets can be detected within 4.7 years." !!!

There was a poster at the Extreme Solar Systems II conference last year by Dumusque et al on Alpha Cen. He stated that "No planet larger than 4 Earth mass with a period shorter than 300 days.” Quite the contrary to previous expectations, isn't it?
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vikingmars
post May 16 2012, 04:46 PM
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QUOTE (IM4 @ May 16 2012, 05:42 PM) *
He stated that "No planet larger than 4 Earth mass with a period shorter than 300 days.” Quite the contrary to previous expectations, isn't it?

Well... For me, it means that they may be planets there, but having masses below 4 Earth mass. When you look to the papers hereabove, all simulations show planets no larger than Earth and even some simulations show the formation of planetary systems with bodies having masses no larger than Mars (for this, please, see page 993 of "Terrestrial Planet Formation in the Alpha Centauri System"). So, there is still an hope smile.gif
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IM4
post May 16 2012, 05:50 PM
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QUOTE (vikingmars @ May 16 2012, 04:46 PM) *
For me, it means that they may be planets there, but having masses below 4 Earth mass. When you look to the papers hereabove, all simulations show planets no larger than Earth and even some simulations show the formation of planetary systems with bodies having masses no larger than Mars

I don't believe in simulations, I love facts. Kepler results suggest that "neptunes" are common in the exoplanetary systems, including binaries. We see no massive planets at Centauri. That's a really bad sign.
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Hungry4info
post May 16 2012, 08:00 PM
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Not in the slightest. Remember if a perfect copy of the inner solar system were around either of the stars at Alf Cen, we wouldn't have detected them yet.


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-- Hungry4info (Sirius_Alpha)
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vikingmars
post May 19 2012, 04:27 PM
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When you look to Kepler's data (please see link : http://kepler.nasa.gov/Mission/discoveries/ ), NO planets having an Earth mass have been (yet) discovered (Earth being 0.00314 Jupiter's mass). As some say, " "neptunes" are common in the exoplanetary systems", it is because "neptunes" are close to the lower limit of Kepler's detectability. Ten years ago we could have say "jupiters" are common... Although we are being close to discover another "earth" (Kepler-20e for example), we will more easily see the ones transiting oftenly in front of their star, which is not the case for Alpha Centauri's A-B system because its orbital inclination (as seen from Earth) is 79.23° : thus, Kepler technique would not work unfortunately for the detection of planets around those two stars. To detect other "earths" orbiting in the life zones of their stars (at 1 AU distance from its star) with Kepler's technique would take some more time. So, I would say : wait a little more for Kepler's stunning results, but do not expect Kepler to detect "earth" planets at 1 AU with great orbital inclinations.
So... Only the techniques funded by TPS could detect planets around the A-B system (with more than 20 nights perhaps..).
=> So be kind to donate, please ! You will be part of the discovery ! smile.gif
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Drkskywxlt
post May 20 2012, 02:17 AM
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There's been a number of Kepler candidates detected with radii equal to or less than Earth's. Mass is obviously the harder number to determine, but it's certainly very likely that at least some of these candidates have masses less than or equal to Earth's.

http://exoplanetarchive.ipac.caltech.edu/c...xotbls?kepler=1
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vikingmars
post May 20 2012, 08:07 AM
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QUOTE (Drkskywxlt @ May 20 2012, 04:17 AM) *
There's been a number of Kepler candidates detected with radii equal to or less than Earth's. Mass is obviously the harder number to determine, but it's certainly very likely that at least some of these candidates have masses less than or equal to Earth's. http://exoplanetarchive.ipac.caltech.edu/c...xotbls?kepler=1

Thanks a lot for this much interesting link. Unfortunately, the "Planet-Star distance" data in AU shows no figures (yet) with "0.8xxx" or "1.xxx"... Those quasi-"earths" discovered are really too close from their parent stars and thus, much too hot. Well, let's wait more time : maybe, by chance, we will discover an "earth" orbiting at 1 AU in the plane of sight of its parent star (orbital inclination = 0° towards us, i.e. towards the Kepler telescope)...
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Drkskywxlt
post May 21 2012, 05:05 PM
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QUOTE (vikingmars @ May 20 2012, 04:07 AM) *
Thanks a lot for this much interesting link. Unfortunately, the "Planet-Star distance" data in AU shows no figures (yet) with "0.8xxx" or "1.xxx"... Those quasi-"earths" discovered are really too close from their parent stars and thus, much too hot. Well, let's wait more time : maybe, by chance, we will discover an "earth" orbiting at 1 AU in the plane of sight of its parent star (orbital inclination = 0° towards us, i.e. towards the Kepler telescope)...


Right. Kepler's original stated criteria was 3 orbits for confirmation of a planet, so a true Earth-analog would have taken a minimum of 3 years to show up in Kepler data. Kepler-22b is the closest to an Earth-analog yet, as it has a ~289 day orbit, but has a radii of 2.4 Earth-radii, making it almost certainly not rocky.
http://arxiv.org/abs/1112.1640

What's complicated everything is the surprising amount of stellar activity in the Kepler field stars. That's why the extended mission is so important, since it will probably take more like 5-6 transits to feel confident in a detection of a planet around these active/jittery stars.
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JRehling
post May 25 2012, 05:47 PM
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Various points:

1) Kepler is reporting almost exclusively (the "Tatooine" discovery withstanding) on single stars. How evolution of double star systems compare is inevitably quite different. Kepler is providing excellent (I would say definitive) evidence that most single stars have planets. Whether or not the same is true of double stars is speculative.

2) The lack of larger planets is not necessarily a bad sign. It may even be a good sign: Large planets at a given orbital distance make it difficult for smaller planets to occupy nearby orbits.

3) Many earth-sized planets have been detected among the candidates from Kepler, and Kepler candidates have a quite low rate of false positives, so many of these are real. But so far, none of those have been confirmed through the radial velocity method. The point is: The transit method is wonderfully sensitive to such planets (and they do exist, in considerable quantity), but the RV method is not.

The great thing about any planetary discovery at Alpha Centauri would be the enhanced opportunity for follow-on science. Any such planet would have 100 times the apparent luminosity of a similar world located 44 light years away. In terms of the proximity of planetary systems, we have to accept the cards the universe has dealt us: rocketry avails us little in terms of getting a better look at objects light years away.

There are seven single star systems with K or G stars within 10 to 20 light years of us. None closer. Then another eighteen from 20 to 30 light years away. Only one other double-star K/G system (61 Cygni, at 11 LY) is within 16 light years. (Epsilon Indi is a K/M pair.) Those are the cards we're dealt. Alpha Centauri represents a unique opportunity to get that close-up science. If the universe didn't give us planets there, the next closest set around a sunlike star has to be significantly farther.
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TheAnt
post May 27 2012, 12:44 PM
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Now we know that planetary objects are quite common around many stars, and that no super Earth have been found in the Alpha Centauri system. I feel its a good idea to have another better look again. So I like this proposal.

As JRehling said, if a planet is found there. We would be given a very good opportunity to study that planet if it is cold and icy in one elliptical orbit or hot and Venus like does not really matter. We will have added a new sample to the group of Earth like planets, and it would give us another example to study. There would be a lot of researchers who would jump onto the bandwagon if one were found, so I guess they would eventually be able to coerce at least some spectrograhic data from it.

And in that I agree with JRehling, it is not likely that we will attempt to send anything there for a closer look by "rocketry" or whatever means we can envision in the foreseeable future.

But if a search like this did find something truly extraordinary, like a planet perfectly placed in the habitable zone and hints of an atmosphere that is not to thin, thick or just plain weird by human standards, it might very well trigger one effort to build a space based TPF - which might give us a look not only for that planet but Earth like planets elsewhere.
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Reed
post May 28 2012, 02:44 AM
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QUOTE (JRehling @ May 25 2012, 09:47 AM) *
1) Kepler is reporting almost exclusively (the "Tatooine" discovery withstanding) on single stars.

I don't believe this is correct. In http://kepler.nasa.gov/Science/about/ScientificGoals/ #3 is determining the frequency of planets in multi-stellar systems.

Even if this weren't an interesting question in it's own right, I don't think they had much choice. Multiple systems are extremely common, and many would not be identifiable in the surveys used to create the target list. The observations needed to characterize the systems and reject false positives will also identify stellar companions.

An example of this followup work is described here http://arxiv.org/abs/1205.5535. As expected, they find many previously undetected stars, and while they can't directly distinguish between bound and background objects, from statistical arguments it's likely some are bound. These probably aren't Alpha Centauri analogs though, at typical Kepler distances the separation would mostly fall below the 0.1 arcsec limit.
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