Comments on: The latest on 55 Cancri http://oklo.org/2007/11/06/the-latest-on-55-cancri/ characterizing planetary systems Fri, 18 Nov 2011 22:27:52 +0000 hourly 1 http://wordpress.org/?v=3.2.1 By: systemic - Just like in 1846 http://oklo.org/2007/11/06/the-latest-on-55-cancri/comment-page-1/#comment-4991 systemic - Just like in 1846 Mon, 02 Jun 2008 22:24:02 +0000 http://oklo.org/?p=256#comment-4991 [...] On the Systemic Backend, there are many candidate planets that have had their orbits characterized. As is usually the case with planet predictions, most of the candidates will wind up being spurious, but it’s definitely true that real planets orbiting real stars have been detected by the Backend user base. For example, Gliese 581 c was accurately characterized by the Systemic users several months before it’s announcement by the Swiss (see this post) and the same holds true for 55 Cancri f (see this post). [...] [...] On the Systemic Backend, there are many candidate planets that have had their orbits characterized. As is usually the case with planet predictions, most of the candidates will wind up being spurious, but it’s definitely true that real planets orbiting real stars have been detected by the Backend user base. For example, Gliese 581 c was accurately characterized by the Systemic users several months before it’s announcement by the Swiss (see this post) and the same holds true for 55 Cancri f (see this post). [...]

]]> By: Bucky http://oklo.org/2007/11/06/the-latest-on-55-cancri/comment-page-1/#comment-3508 Bucky Fri, 09 Nov 2007 05:28:28 +0000 http://oklo.org/?p=256#comment-3508 I reacted exactly as Andy did when I saw this news the other day – drat, there goes that lovely hypothetical Earth twin that was supposed to be orbiting around 1 AU. And yes, the new planet seems too small to have big moons – although in that regard, nobody has really studied how satellite systems might form around giant planets that migrate into Earthlike orbits. Could all the rocky planetesimals in that region of the disk alter the mass ratio between planet and moon? (That is, if Planet f really did migrate there – Fischer & company seem to leave open the possibility of in situ formation.) It'll be interesting to see what evolutionary models the theoreticians can concoct now that 55 Cancri's inner system architecture is so well constrained. And now that we know that the system's habitable zone is full, are there any other good candidate systems with a Jupiter analog and a giant-free HZ? The likeliest one I know of is HD 154345, which is only a little farther away than 55 Cancri. Exoplanets.org initially listed it with a high orbital eccentricity and a very large semimajor axis, but they currently give e = 0.05 and a = 4.17 AU. However, I don't think there's even a discovery paper on that one. I'm really curious to know more, if there's any more to know. I reacted exactly as Andy did when I saw this news the other day – drat, there goes that lovely hypothetical Earth twin that was supposed to be orbiting around 1 AU. And yes, the new planet seems too small to have big moons – although in that regard, nobody has really studied how satellite systems might form around giant planets that migrate into Earthlike orbits. Could all the rocky planetesimals in that region of the disk alter the mass ratio between planet and moon? (That is, if Planet f really did migrate there – Fischer & company seem to leave open the possibility of in situ formation.)

It’ll be interesting to see what evolutionary models the theoreticians can concoct now that 55 Cancri’s inner system architecture is so well constrained.

And now that we know that the system’s habitable zone is full, are there any other good candidate systems with a Jupiter analog and a giant-free HZ? The likeliest one I know of is HD 154345, which is only a little farther away than 55 Cancri. Exoplanets.org initially listed it with a high orbital eccentricity and a very large semimajor axis, but they currently give e = 0.05 and a = 4.17 AU. However, I don’t think there’s even a discovery paper on that one. I’m really curious to know more, if there’s any more to know.

]]> By: tacitus http://oklo.org/2007/11/06/the-latest-on-55-cancri/comment-page-1/#comment-3475 tacitus Thu, 08 Nov 2007 00:26:39 +0000 http://oklo.org/?p=256#comment-3475 So, what are the odds of finding a more than one planet around the same star using light curves, say, with using the COROT probe? So, what are the odds of finding a more than one planet around the same star using light curves, say, with using the COROT probe?

]]> By: andy http://oklo.org/2007/11/06/the-latest-on-55-cancri/comment-page-1/#comment-3461 andy Wed, 07 Nov 2007 16:59:24 +0000 http://oklo.org/?p=256#comment-3461 devicerandom: it does if the relationship between the mass of a gas giant and the mass of its moon system holds in the 55 Cancri system as well as in our own. Keeping the moon:planet mass ratio the same, scaling down Titan or scaling up Triton yields a moon of about a lunar mass. Scaling Ganymede or Titania gives rather smaller moons. I wonder if the Trojan points are stable? devicerandom: it does if the relationship between the mass of a gas giant and the mass of its moon system holds in the 55 Cancri system as well as in our own. Keeping the moon:planet mass ratio the same, scaling down Titan or scaling up Triton yields a moon of about a lunar mass. Scaling Ganymede or Titania gives rather smaller moons.

I wonder if the Trojan points are stable?

]]> By: Eric F Diaz http://oklo.org/2007/11/06/the-latest-on-55-cancri/comment-page-1/#comment-3457 Eric F Diaz Wed, 07 Nov 2007 15:14:41 +0000 http://oklo.org/?p=256#comment-3457 Thanks, Greg. Best, Eric Thanks, Greg.

Best,
Eric

]]> By: devicerandom http://oklo.org/2007/11/06/the-latest-on-55-cancri/comment-page-1/#comment-3456 devicerandom Wed, 07 Nov 2007 14:48:40 +0000 http://oklo.org/?p=256#comment-3456 @Andy: it does not rule out terrestrial-mass <i>moons</i>, however, in the habitable zone :) @Andy: it does not rule out terrestrial-mass moons, however, in the habitable zone :)

]]> By: andy http://oklo.org/2007/11/06/the-latest-on-55-cancri/comment-page-1/#comment-3449 andy Tue, 06 Nov 2007 21:43:54 +0000 http://oklo.org/?p=256#comment-3449 Further question comes to mind: have radial velocity measurements of the companion star to 55 Cancri been made? Are there any constraints on planets around it? Further question comes to mind: have radial velocity measurements of the companion star to 55 Cancri been made? Are there any constraints on planets around it?

]]> By: andy http://oklo.org/2007/11/06/the-latest-on-55-cancri/comment-page-1/#comment-3448 andy Tue, 06 Nov 2007 20:03:26 +0000 http://oklo.org/?p=256#comment-3448 Fantastic result, but it's a pity this rules out terrestrial-mass planets in the habitable zone. Given the importance of planet-planet interactions over the timescale of the data, perhaps it would be useful to also have radial velocity datasets scaled up to account for the astrometric inclination measurements of the system, to see what effect that has on the solution. Fantastic result, but it’s a pity this rules out terrestrial-mass planets in the habitable zone.

Given the importance of planet-planet interactions over the timescale of the data, perhaps it would be useful to also have radial velocity datasets scaled up to account for the astrometric inclination measurements of the system, to see what effect that has on the solution.

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