Comments on: Lobbying for Alpha Cen http://oklo.org/2009/08/29/lobbying-for-alpha-cen/ characterizing planetary systems Fri, 18 Nov 2011 22:27:52 +0000 hourly 1 http://wordpress.org/?v=3.2.1 By: pete j http://oklo.org/2009/08/29/lobbying-for-alpha-cen/comment-page-1/#comment-32313 pete j Fri, 11 Sep 2009 20:37:03 +0000 http://oklo.org/?p=353#comment-32313 A closing comment on Alpha Cen – and the question of water, perhaps there is an AlphaCen Oort cloud, which delivers comets (therefore water) to any inner terrestrials around A and B. If I’m not mistaken this mechanism is likely not to be as efficient as the delivery in our Solar System. The studies of Wiegert & Holman (1997) reveal that a single planet on a circular orbit is unstable over much of the region of the central AlphaCentauri Binary. However, there are zones in which such a planet could be stable over million year time scales. These zones are located both far from the binary (a >=70au) and near to (a <=3au) the primary and the secondary. Therefore the delivery (additional water) could only be from this region. A closing comment on Alpha Cen – and the question of water, perhaps there is an AlphaCen Oort cloud, which delivers comets (therefore water) to any inner terrestrials around A and B. If I’m not mistaken this mechanism is likely not to be as efficient as the delivery in our Solar System.

The studies of Wiegert & Holman (1997) reveal that a single planet on a circular orbit is unstable over much of the region of the central AlphaCentauri Binary. However, there are zones in which such a planet could be stable over million year time scales. These zones are located both far from the binary (a >=70au) and near to (a <=3au) the primary and the secondary. Therefore the delivery (additional water) could only be from this region.

]]> By: andy http://oklo.org/2009/08/29/lobbying-for-alpha-cen/comment-page-1/#comment-30405 andy Mon, 31 Aug 2009 21:31:53 +0000 http://oklo.org/?p=353#comment-30405 Talking of the console, how's the work on the backend part of the site going? Talking of the console, how’s the work on the backend part of the site going?

]]> By: bruce01 http://oklo.org/2009/08/29/lobbying-for-alpha-cen/comment-page-1/#comment-30305 bruce01 Mon, 31 Aug 2009 13:08:39 +0000 http://oklo.org/?p=353#comment-30305 My experience using the console with two or more data sets usually results in a poorer fit than if all the data came from one instrument. This indicates to me that there are more instrumental corrections, besides a single rv bias, that need to be incorporated into the fit. The more precise the individual rv observations become, the more important systematic instrumental effects become. So, whether pooling data helps depends upon how well the systematic effects can be eliminated from the rv observations. My experience using the console with two or more data sets usually results in a poorer fit than if all the data came from one instrument. This indicates to me that there are more instrumental corrections, besides a single rv bias, that need to be incorporated into the fit. The more precise the individual rv observations become, the more important systematic instrumental effects become. So, whether pooling data helps depends upon how well the systematic effects can be eliminated from the rv observations.

]]> By: Lab Lemming http://oklo.org/2009/08/29/lobbying-for-alpha-cen/comment-page-1/#comment-30176 Lab Lemming Mon, 31 Aug 2009 06:31:51 +0000 http://oklo.org/?p=353#comment-30176 How much faster could they get a detection if the competing teams pooled their data and collaborated? How much faster could they get a detection if the competing teams pooled their data and collaborated?

]]> By: greg http://oklo.org/2009/08/29/lobbying-for-alpha-cen/comment-page-1/#comment-30175 greg Mon, 31 Aug 2009 04:34:08 +0000 http://oklo.org/?p=353#comment-30175 Hi Coolstar, Debra Fischer (with Geoff Marcy as a collaborator) is indeed running a competing program on Alpha Cen from the southern hemisphere. From what I hear, it's progressing quite well -- I think it's important though, for a discovery of this importance, to have two competing teams. You can read the details in both the Seed article, as well as in the google translation of the FAZ article. cheers, Greg Hi Coolstar,

Debra Fischer (with Geoff Marcy as a collaborator) is indeed running a competing program on Alpha Cen from the southern hemisphere. From what I hear, it’s progressing quite well — I think it’s important though, for a discovery of this importance, to have two competing teams.

You can read the details in both the Seed article, as well as in the google translation of the FAZ article.

cheers,
Greg

]]> By: coolstar http://oklo.org/2009/08/29/lobbying-for-alpha-cen/comment-page-1/#comment-30173 coolstar Mon, 31 Aug 2009 03:22:00 +0000 http://oklo.org/?p=353#comment-30173 Thanks Andy and Greg: that really should have occurred to me. I need to look up the orbital separations, I guess. I thought the Marcy group was also doing the Alpha Cen system from Chili but have I mis-remembered that? Thanks Andy and Greg: that really should have occurred to me. I need to look up the orbital separations, I guess. I thought the Marcy group was also doing the Alpha Cen system from Chili but have I mis-remembered that?

]]> By: greg http://oklo.org/2009/08/29/lobbying-for-alpha-cen/comment-page-1/#comment-30172 greg Mon, 31 Aug 2009 01:30:01 +0000 http://oklo.org/?p=353#comment-30172 Hi Coolstar, Regarding water in the Alpha Cen system, I'm in full agreement with Andy's comment. For Alpha Cen, yes, you need to be in the Southern hemisphere -- Antarctica would be a fine location, although the usual observing sites in Chile, Southern Africa and Australia are also all close to ideal, and are likely more cost-effective. The season on Alpha Cen, for example, at CTIO is close to ten months. cheers, Greg Hi Coolstar,

Regarding water in the Alpha Cen system, I’m in full agreement with Andy’s comment.

For Alpha Cen, yes, you need to be in the Southern hemisphere — Antarctica would be a fine location, although the usual observing sites in Chile, Southern Africa and Australia are also all close to ideal, and are likely more cost-effective. The season on Alpha Cen, for example, at CTIO is close to ten months.

cheers,
Greg

]]> By: Lab Lemming http://oklo.org/2009/08/29/lobbying-for-alpha-cen/comment-page-1/#comment-30166 Lab Lemming Mon, 31 Aug 2009 00:04:25 +0000 http://oklo.org/?p=353#comment-30166 What is the minimum altitude you need to do RV measurements? Would a more southerly scope give you more opportunities? You mentioned previously that a 1-2m scope would be sufficient, due to the brightness of the star. Are there any 1m scopes at any of the Antarctic bases that you could fly a spectrometer down to? What is the minimum altitude you need to do RV measurements? Would a more southerly scope give you more opportunities? You mentioned previously that a 1-2m scope would be sufficient, due to the brightness of the star. Are there any 1m scopes at any of the Antarctic bases that you could fly a spectrometer down to?

]]> By: andy http://oklo.org/2009/08/29/lobbying-for-alpha-cen/comment-page-1/#comment-30095 andy Sun, 30 Aug 2009 10:26:31 +0000 http://oklo.org/?p=353#comment-30095 The problem with Alpha Centauri and water is that the snow line around each of the components is rather close to the region where the orbits become unstable. This suggests the water reserves in the circumstellar discs were quite small. The problem with Alpha Centauri and water is that the snow line around each of the components is rather close to the region where the orbits become unstable. This suggests the water reserves in the circumstellar discs were quite small.

]]> By: coolstar http://oklo.org/2009/08/29/lobbying-for-alpha-cen/comment-page-1/#comment-30020 coolstar Sun, 30 Aug 2009 05:03:13 +0000 http://oklo.org/?p=353#comment-30020 Care to elaborate on how we can be so sure there were not substantial quantities of water in the Alpha Cen system? I'm pretty mystified as to how we can know this? Care to elaborate on how we can be so sure there were not substantial quantities of water in the Alpha Cen system? I’m pretty mystified as to how we can know this?

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