[mesa-users] A problem in making planets

[Chris Mankovich]

Hi Songhu,

I suspect Aaron's guess is probably correct, although it's hard to say
conclusively without seeing your inlist.

The routine build_initial_model (in star/private/create_initial_model.f90)
attempts to find a hydrostatic, isentropic starting model matching the
total mass and radius specified by the user. It does this iteratively,
making a series of guesses for the central entropy and pressure and
integrating the structure equations out to the surface.

What this means is that small changes to the guess for central entropy or
pressure could potentially lead to surface temperatures outside the domain
covered by the available EOS. In particular, a 1 M_J planet at 1 R_J with
no irradiation (the default inlist_create_1.0_MJ_10.0_ME_2.0_RJ includes no
irradiation, since it's really intended for creating a young, hot planet)
has surface temperatures of order 100 K, so it's easy for a slightly lower
guess for the central entropy to throw the surface far off the EOS tables.

I'd echo Aaron's suggestion that you try a more inflated initial model.
Then you could allow it to cool to 1 R_J (and possibly beyond) by just
letting it evolve.


chris

On Mon, Jan 30, 2017 at 3:28 PM, Aaron Dotter <aaron.dotter at gmail.com>
wrote:

> Hi,
>
> It's a good idea to send your inlists along with your email describing the
> problem.  This let's others try to reproduce your error.
>
> That said, my guess is that your are at or beyond the EOS limits.  Have
> you tried intermediate values between 2R_J and 1 R_J?
>
> Aaron
>
>
>
> On Monday, January 30, 2017, Songhu Wang <songhuwang86 at gmail.com> wrote:
>
>> Hi all,
>>
>> These days, I try to conduct some planetary evolution work using MESA,
>> although most of my previous work focus on observations.
>> There is a developed demo case, named 'make_planets', in star/test_suite
>> in released mesa directory (I use mesa-r8845).
>>
>> In this demo case, we need three steps to build and evolve a planet:
>> 1. create an atmosphere envelop (inlist_create)
>>
>> 2. insert a core (inlist_core)
>>
>> 3. evolve (inlist_evolve)
>>
>> Now, I have a problem in the first step.
>> In the demo case, they try to build a 2R_J planet (
>> radius_in_cm_for_create_initial_model) with 1M_J (
>> mass_in_gm_for_create_initial_model).
>>
>> I can run this demo smoothly, but when I try to use 1R_J as initial
>> planet radius (radius_in_cm_for_create_initial_model), I found no matter
>> what initial planet mass I choose, I can not run the code anymore.
>>
>> The reported error is attached.
>> [image: Inline image 1]
>> Can you give me some suggestions?
>>
>>
>> Thank you,
>> Songhu Wang
>> -----------------------------------
>> 51 Pegasi b Fellow in Yale
>>
>
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