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  #241 (permalink)  
Old 26-May-2008, 08:11 PM
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Originally Posted by 01101001 View Post
COROT has also detected extremely faint signals that, if confirmed, could indicate the existence of another exoplanet, as small as 1.7 times Earth’s radius.[/url]
I just read about this on an article on a danish site by the most famous danish astronomer these days, Michael Linden-Vørnle. I searched a little around here on BAUT and saw your quoting. Can you, or anyone else, provide me (us) with more imformation on this? I know information about unconfirmed discoveries are little, but i'm so thrilled about it i wouldn't mind reading about something that i would later find out isn't true
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  #242 (permalink)  
Old 26-May-2008, 09:04 PM
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Is this a technique used to discover planets, or observe them after discovery?
After.
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  #243 (permalink)  
Old 26-May-2008, 10:12 PM
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Yep, that makes sense.
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  #244 (permalink)  
Old 26-May-2008, 10:52 PM
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Can you, or anyone else, provide me (us) with more imformation on this?
I only repeated what I read in the ESA press release. It was quite surprising to read something so significant that seemed so unsubstantiated.

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COROT has also detected extremely faint signals that, if confirmed, could indicate the existence of another exoplanet, with a radius as small as 1.7 times that of Earth.
All I looked at about it on the web, are links back to the same ESA release.

Maybe someone else knows more about it. Or, we wait...
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  #245 (permalink)  
Old 26-May-2008, 11:37 PM
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Didn't even read the ESA press release, so thx for the link. But hard to wait when it is such an exciting subject. Unfortunately they haven't got any more info on this planet.

How long can we expect it takes from the first observations of an exoplanet until it is confirmed?
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  #246 (permalink)  
Old 27-May-2008, 06:24 AM
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George,

So, that subset must be equal to around 150 stars? Since 45/150 X 100= 30%. But it said in Greg Laughlin's post that 400 stars were non-active FGK type stars. Why then, if they are non-active, were 250 stars excluded from analysis?

In the article it says that 10% of sun-like stars have hot-Jupiters (jovians closer to their stars than Mercury is to the Sun), but only 1% have planets of this size and orbital separation.

I can't help but think that something is wrong with the information presented in this article...
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Old 27-May-2008, 02:09 PM
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I read it as the 30% includes two planetary populations: SuperEarths and hot Neptunes. They say...

"The notion that 30 percent of all sunlike stars have close-in superEarths or superNeptunes is “really remarkable."

The 45 only applies to the number of SuperEarths of the 400 stars in the study.

When you add the additional 10% for the third Jupiter class of planets to the 30% for the other two, we get 40% for all three classes. Thus, 40% of all sun-like stars have planets. I assume this percentage will be higher once the Earth-sized planets are detectable. Perhaps more than half of the F, G, and K class stars will be discovered to have planets.

The articles are little unclear of these numbers, admittedly. But I think I'm right. It would have been nicer to break it down as follows:

Of the 400 sun-like stars, at least...

11% have SuperEarths planets
19% have Neptune class planets
10% have Jupiter class planets
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  #248 (permalink)  
Old 12-June-2008, 04:16 PM
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Some recent discoveries:
  • MOA-2007-BLG-192Lb, as already discussed on this forum, marks the discovery of the first planet less massive than the two massive terrestrials around the pulsar PSR 1257+12. The third planet, PSR 1257+12 A (discovered in 1994, before 51 Pegasi b!) has a mass comparable that of the Moon and remains as the by far smallest known extrasolar planet, a title it has held for almost one and half decades despite misleading PR releases.
  • The orange giant HD 102272 has a planetary system consisting of two massive Jovians. The outer planet orbits in a very eccentric orbit.

The discovery of MOA-2007-BLG-192Lb is remarkable in two ways: firstly, it suggests that terrestrials may form around the smallest stars and brown dwarfs, and that such planets may be very common. Secondly, our ability to detect that small deviations in gravitational lensing curves implies that the first true extrasolar Earth analogs will be found rather soon. Indeed, there are already rumors of such detections although they're not yet confirmed. But it does seem that terrestrial planets are very common also around more "normal" stars.
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  #249 (permalink)  
Old 16-June-2008, 09:40 AM
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Five super-Earths around three stars, courtesy of HARPS:
  • HD 40307 (K dwarf) has a system of three super-Earths. HD 40307 b has a mass of mere 4.2 Earths so it is the smallest planet found by the radial velocity method so far.
  • HD 181433 (K giant) has a closely-orbiting super-Earth and a much more distant gas giant.
  • HD 47186 (late G dwarf) has a somewhat similar system.
Since the super-Earths orbit close to their stars (in the case of HD 40307 the orbital period of the outermost planet is 20.45 days!), and the stars are not red dwarfs they are by far too hot to be habitable.

According to the Extrasolar Planets Encyclopaedia, the total number of planet candidates is now 303.
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  #250 (permalink)  
Old 16-June-2008, 01:20 PM
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300+ and climbing.
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  #251 (permalink)  
Old 16-June-2008, 03:34 PM
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ESO press release
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  #252 (permalink)  
Old 16-June-2008, 05:19 PM
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According to the Universe Today article about the star with three super-earths in orbit around it, it appears that those orbits are pretty circular. I wonder if there's still the possibility of a more earth-like planet lurking in a more earth-like orbit around that star.
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  #253 (permalink)  
Old 16-June-2008, 05:44 PM
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It is quite likely that these planets didn't form in their current positions. Although it looks likely that terrestrial planets can form after the migration of a gas giant, the situation may be different in the case of (super-)terrestrial planets which form later. But there's certainly room left for habitable planets. Unfortunately, detecting an Earth-sized planet in the star's habitable zone is very difficult.
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  #254 (permalink)  
Old 16-June-2008, 10:26 PM
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More from the systemic blog:

Quote:
He [Michel Mayor] predicts 1 to 1.5 Earth sensitivity by around 2010 (extrapolating a trend).
As it was told earlier, the announced planets are only a tip of the iceberg...

Quote:
He says he has 40 new candidates in the 30-50 day period range, and mass less than 30 Earths.
With that number of super-Earth/Neptune candidates, odds for the discovery of a new transiting planet is almost certain.

Quote:
[HARPS] [c]an do 0.5 m/s today, 0.1 m/s in near future.
This should be enough to detect our planet... too bad true solar analogs are probably too noisy spectrally. That's why super-Earth systems are mostly being found around orange and red dwarfs instead of Sun-like G stars.
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  #255 (permalink)  
Old 18-June-2008, 02:30 AM
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Originally Posted by Kullat Nunu View Post
This should be enough to detect our planet... too bad true solar analogs are probably too noisy spectrally. That's why super-Earth systems are mostly being found around orange and red dwarfs instead of Sun-like G stars.
You mean "... from another star"? This really is exciting.

I will repeat a former question of mine i didn't get an answer to, but i expect that so,eone knows:

"How long can we expect it takes from the first observations of an exoplanet until it is confirmed?"
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  #256 (permalink)  
Old 18-June-2008, 06:02 AM
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Default Possible "Super-Earth" discrepancy looming?

Has anyone read the NYTimes article discussing the discovery of these super-Earths? The article was written by Denis Overbye and is called "A Bounty of Midsize Planets Is Reported."

In this article the American team led by Geoff Marcy issued the following statement regarding the Swiss team's finding (Overbye described the statement as "terse"):

"Our survey will check the Swiss report that 30 percent of stars have super-Earths or Neptunes orbiting closer than Mercury does the Sun...”

Now, obviously the wording is ambiguous, but notice what the American team did not say. They did not say something like "although our study is not yet complete, we can say that our preliminary data roughly corroborate the Swiss finding..." So, I wonder if the American team, whose results will be published in a year or two, are in conflict with the result just reported that "30 percent of stars have Super-Earths." To my knowledge, the conclusions reached by these two radial velocity searches have been roughly equivalent up until this point so a significant discrepancy may call into question the robustness of high precision radial velocity searches for extrasolar planets.

Or, perhaps Marcy et al will publish results which are consistent with these new results. Or, perhaps Marcy et al were just slightly miffed that they were not the first to find so many super-Earths.

Has anyone heard anything about a discrepancy looming between the results reached by the American team and the new results from the Swiss team other than what is hinted at in the NYTimes article?
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  #257 (permalink)  
Old 18-June-2008, 02:51 PM
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Quote:
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You mean "... from another star"?
I meant a planet like ours around a Sun-like star. Same thing.

Quote:
Originally Posted by Sporally View Post
"How long can we expect it takes from the first observations of an exoplanet until it is confirmed?"
Time? Preferably a full orbital period so that the orbit can be determined definitely. Number of data points? Depends on the signal. A hot Jupiter should be detectable using only relatively few data points, a smaller planet needs more. So a hot Jupiter signal should be clear in only a few weeks (few orbits). According to Greg Laughlin, a super-Earth needs about 25 times as many as data points as a gas giant. Which means it takes a much longer time to confirm a super-Earth than a jovian planet.
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  #258 (permalink)  
Old 18-June-2008, 02:53 PM
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Quote:
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"Our survey will check the Swiss report that 30 percent of stars have super-Earths or Neptunes orbiting closer than Mercury does the Sun...”
Unless I'm mistaken, they don't have an instrument as accurate as HARPS. But on the other hand, they too have found some super-Earths so we shall see.
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