Comments on: Oligarchic Growth http://oklo.org/2006/04/30/oligarchic-growth/ characterizing planetary systems Fri, 18 Nov 2011 22:27:52 +0000 hourly 1 http://wordpress.org/?v=3.2.1 By: Centauri Dreams » Blog Archive » Red Dwarfs: Dust, Details and Habitability http://oklo.org/2006/04/30/oligarchic-growth/comment-page-1/#comment-4744 Centauri Dreams » Blog Archive » Red Dwarfs: Dust, Details and Habitability Mon, 31 Mar 2008 14:53:23 +0000 http://oklo.org/?p=72#comment-4744 [...] But note another assumption I’ve made above, one that could stand some scrutiny. I’ve set up one in a thousand as a figure for habitable planet occurrence without any reference to how planets form in the first place. A key question is whether we can assume roughly similar methods of planet formation around M dwarfs as around G stars and the other stellar types. We’re studying models like core accretion and gravitational instability as we develop consistent theories for all this, but our knowledge of what goes on around M dwarfs remains sparse. [...] [...] But note another assumption I’ve made above, one that could stand some scrutiny. I’ve set up one in a thousand as a figure for habitable planet occurrence without any reference to how planets form in the first place. A key question is whether we can assume roughly similar methods of planet formation around M dwarfs as around G stars and the other stellar types. We’re studying models like core accretion and gravitational instability as we develop consistent theories for all this, but our knowledge of what goes on around M dwarfs remains sparse. [...]

]]> By: systemic - Lonely Planet Guide to the Hyades http://oklo.org/2006/04/30/oligarchic-growth/comment-page-1/#comment-1111 systemic - Lonely Planet Guide to the Hyades Fri, 09 Feb 2007 08:10:04 +0000 http://oklo.org/?p=72#comment-1111 [...] My guess is that Epsilon Tauri b is an example of a planet that formed through the gravitational instability mechanism. Gravitational instability should generally produce more massive planets (e.g. HIP 75458 b, and HD 168443 b and c) and its efficacy will be little-affected by UV radiation from neighboring stars. It likely occurs once per every several hundred stars that are formed, and so it’s perfectly reasonable that there’s one star in the Hyades that has a planet formed via the GI mechanism. For more information, this series: 1, 2, 3, 4, 5, 6, and 7 of oklo posts that compare and contrast the gravitational instability and core accretion theories for giant planet formation. [...] [...] My guess is that Epsilon Tauri b is an example of a planet that formed through the gravitational instability mechanism. Gravitational instability should generally produce more massive planets (e.g. HIP 75458 b, and HD 168443 b and c) and its efficacy will be little-affected by UV radiation from neighboring stars. It likely occurs once per every several hundred stars that are formed, and so it’s perfectly reasonable that there’s one star in the Hyades that has a planet formed via the GI mechanism. For more information, this series: 1, 2, 3, 4, 5, 6, and 7 of oklo posts that compare and contrast the gravitational instability and core accretion theories for giant planet formation. [...]

]]> By: systemic - G.I. No http://oklo.org/2006/04/30/oligarchic-growth/comment-page-1/#comment-99 systemic - G.I. No Tue, 02 May 2006 02:28:09 +0000 http://oklo.org/?p=72#comment-99 [...] In a comment on yesterday’s core-accretion post, a reader anticipated that all is not hunky-dory with the core-accretion scenario for the formation of the gas giant planets in our solar system, and asked if is there any support for Alan Boss’ disk instability model. In the Boss model (described here by Alan, see also the buff 137-strong citation list) gas giant planets condense directly out of the protostellar disk as the result of gravitational instability in the disk. [...] [...] In a comment on yesterday’s core-accretion post, a reader anticipated that all is not hunky-dory with the core-accretion scenario for the formation of the gas giant planets in our solar system, and asked if is there any support for Alan Boss’ disk instability model. In the Boss model (described here by Alan, see also the buff 137-strong citation list) gas giant planets condense directly out of the protostellar disk as the result of gravitational instability in the disk. [...]

]]> By: TheoA http://oklo.org/2006/04/30/oligarchic-growth/comment-page-1/#comment-98 TheoA Mon, 01 May 2006 21:57:29 +0000 http://oklo.org/?p=72#comment-98 Is there any support for Alan Boss’s disk instability model. This gradual accretion has difficulty explaining Uranus & Neptune. There is much speculation that Jupiter, Saturn, Uranus and Neptune did not / could not form in their present locations. From the recent discoveries it is pretty obvious that planet formation is not a ‘clean’ process. The end result seems to not have very little resemblance to the formative structure. Why must we expect our system to have bucked the trend. The Uranus tilt alone should make us a little suspicious of the present calm. Also is there a role for the large planetisimals like sedan & xena that are suspected to have come from elsewhere in this process. One should suspect so, esp. considering the sheer number of them estimated to be out there. This could help skip the early ‘squishy’ parts of planet formation. The recent images of dust gaps have been at 70+ AU from their parent stars. To one who grew up thinking Pluto was the end of planet formation this is fascinating. There are so many more options for the process are there not. Nature continues to bewilder. Is there any support for Alan Boss’s disk instability model. This gradual accretion has difficulty explaining Uranus & Neptune. There is much speculation that Jupiter, Saturn, Uranus and Neptune did not / could not form in their present locations.

From the recent discoveries it is pretty obvious that planet formation is not a ‘clean’ process. The end result seems to not have very little resemblance to the formative structure. Why must we expect our system to have bucked the trend. The Uranus tilt alone should make us a little suspicious of the present calm.

Also is there a role for the large planetisimals like sedan & xena that are suspected to have come from elsewhere in this process. One should suspect so, esp. considering the sheer number of them estimated to be out there. This could help skip the early ‘squishy’ parts of planet formation.

The recent images of dust gaps have been at 70+ AU from their parent stars. To one who grew up thinking Pluto was the end of planet formation this is fascinating. There are so many more options for the process are there not. Nature continues to bewilder.

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