View Full Version here: : Exoplanet Environments
17-02-2011, 09:32 AM
Well, following up on the Kepler 'Candidate' planets - 54 possibly in the 'Habitable Zone', comes this interesting article which asks the question:
"How do we determine the nature of the environments on the exo-planets ?"
Violent storms on alien planets (http://www.physorg.com/news/2011-02-violent-storms-alien-planets.html)
He has developed a model which can replicate conditions in Earth's atmosphere 'correctly' and can also produce similar results for the exoplanets he studied. And they say his calculations are, at least, in same order of magnitude based on absorption line frequency shifts.
.. A good effort, and another small step in the right direction, in my opinion.
But let's not forget the extraordinary diversity of exo-environments, as supported by direct evidence from our our own solar system observations. How do you incorporate that in a model ?
17-02-2011, 10:47 AM
You may need several models to explain all the environments. It may not be possible to reduce it all down into one.
17-02-2011, 11:02 AM
You know what gets me with what is said these days..."scientists are surprised at......". That is either beat up for the news bulletins or they're not as smart as they think they are. In some cases it's a genuine surprise at what they find, but for the most part, just a little bit of logical thinking would've told them what was going on. If they're incapable of doing that and find themselves scratching their heads over situations a competent high school science student could figure out, then they shouldn't be doing science.
Anyone with half a brain could've told them why the hot spots on these Hot Jupiters were offset from the antisolar point. It's simple physics and a little bit of deductive reasoning.
17-02-2011, 11:09 AM
Personally i wouldn't be surprised it being more a media beef up
17-02-2011, 11:13 AM
No Mal, it's the scientists for much of the time, although the media doesn't help considering how science illiterate they are.
17-02-2011, 01:58 PM
I think you're significantly under-valuing the research/modelling being done on this occasion.
Atmospheric modelling at the best of times (for Earth, even), is an extraordinarily complex undertaking.
These guys are developing a quantitative model for distant exo-planets, taking into consideration non-linearity aspects of fluid dynamics at different atmospheric depths.
Whilst I feel that all such atmospheric models are based on familiar conditions extrapolated from planet Earth experiences and hence, actual model parameters may end up varying significantly from assumed values, the models have significant atmospheric physical foundations.
These guys are no slouches in the intellectual department, as a cursory glance at their report reveals.
Their technique uses a comparison between two advanced, substantial models, as a measure of validation of the conclusions. Such an approach also suggests a depth of understanding of scientific methodologies, also.
17-02-2011, 02:29 PM
No I'm not, Craig.
I'm very much aware of the abilities of the scientists and the complexities of the physical processes they're trying to model.
What I am on about is the reasoning abilities of some of these scientists. They're so far into the science and the modeling that they can't see the forest for the trees. They get too complex and complicated before they nut out the basics of the physical processes. Instead of trying to be too intellectual about a problem, they need to step back and think about the basic processes or even speculate about what's probably happening in the first place instead of being surprised about something that should be rather obvious to work out.
If the hot spot which is supposed to be at the antisolar point is offset, then there are a couple of explanations...migration due to large scale turbulence generated by internal forces and/or shallow atmospheric phenomena (i.e. wind/atmospheric circulation). Nothing surprising about that and something that should be expected, given that these planets are being heated (in some cases) to over 2000 degrees and wind velocities approaching 2-4km/s have been determined. These hot spots are most likely being influenced by the interactions between the internal turbulence and the wind shear in the atmospheres of these planets. The amount of offset would be determined by the boundary between the laminar flow of the wind shear and the turbulence being generated as well as isothermal gradients between these zones and the heat transport mechanisms present. It becomes a complex dance between how the heat is being distributed about the planet and the interactions between the atmospheric and internal planetary processes driving the circulation.
It's understanding those models where all the crucial physics and maths enters into the science, not beforehand. It's like putting the cart before the horse. You only need to know why something is possibly/probably happening at first, not the detailed physics behind it...that comes later. You don't work out the thermodynamics and such before saying, "Well, that's why it's happening". You hypothesise first, then do the brain work later.
17-02-2011, 05:28 PM
Ok. I understand where you're coming from, now.
I also notice that your words don't necessarily apply to the guys who compared these particular models, either (?). Re-reading the journo article, and the published paper, the words about 'surprising findings' only appear in the journo article. From the published paper, nothing particularly surprised the scientists doing the modelling.
One of the aspects they drew attention to is that the initial values assigned to a parameter called 'horizontal dissipation', which translates to 'hyperviscous dissipation rate and time' parameters in the models, can result in agreement between the models, by arbitrarily adjusting the values adopted. They also explain that the magnitude of the horizontal dissipation cannot yet be specified from first principles, which leads to a limitation of their ability to accurately model the atmospheres, especially wind velocities.
Direct wind measurements from transit observations of extrasolar planets is what they need … which highlights the need to link the models back into the real exo-planet world.
I whole-heartedly agree that linkages of models back into the real world, is crucial .. and I might even admit .. is of first order importance in the modelling game. How many times have we seen certain groups of folk create an 'equivalent model' which is reasonably consistent within the bounds of the model .. but has no evidence or quantified relationships with the real physical world ?
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