[ExI] More Tabby's Star news

Anders anders at aleph.se
Sun Aug 7 21:27:54 UTC 2016

Remember that when a planet makes a transit, it can reduce the light by 
a factor of 1%. Put it in the atmosphere and it soon heats up to about 
the same temperature, reducing the light a lot less.

(How soon? Jupiter is 0.000949 of the sun's mass. Most of it is *hotter* 
than the sun's surface, so freed from gravitational confinement the core 
will definitely mix pretty explosively - the gravitational binding 
energy of 2e33 J is about 62 days of solar energy production... I would 
say the result would be transient and bright. A terrestrial world would 
just dissolve in a few hours.)

One way of detecting recently swallowed planets is to look for Li6: 

On 2016-08-07 21:47, Dan TheBookMan wrote:
> Just pure speculation on my part, but I was thinking a large object -- say a big Jupiter or a brown dwarf -- falls into the star X years ago -- where X is the number of years needed for it to dim the star enough. (In other words, we're not seeing the actual collision, but only the aftermath (even adding to light travel time and all that), however long that took. Of course, this is adjusting the hypothesis to fit the data, but that's not verboten, right? All one need do then is look for independent evidence of this -- as opposed to just adding ever more epicycles.)
> I'm only offering this up as a speculation here too. I don't know what happened, and you might be correct. It's simply something rather mundane going on. All the neat stuff -- if you like that sort of thing* -- in Saturn's rings seems to be caused by collisions and gravity rather than anything exotic.
> I'm guessing the folks doing this work are looking at similar stars to see if there's some pattern or whether Tabby's Star is unique.
> Regards,
> Dan
> Sample my latest Kindle book,
> "The Late Mr. Gurlitt," at:http://mybook.to/Gurlitt
> * I don't. I find these planetary rings garish.
> From: Anders <anders at aleph.se>To: extropy-chat at lists.extropy.org
> Sent: Saturday, August 6, 2016 5:43 AM
> Subject: Re: [ExI] More Tabby's Star news
> A planet shouldn't dim a star much. To dim it you need to reduce the rate of fusion reactions, typically by making it less dense - planets instead add opaque and dense "metals" (astronomer slang for "not hydrogen and helium") that heat things up. Besides, the components of a dissolved planet would take ages to reach the core.
> I think the cause is some mundane astrophysics, but there is room
>    for a lot of weird effects from mundane astrophysics. Just consider
>    stellar oscillations, where all sorts of nonlinear things happen.
>    Maybe this is the first case of a super-long periodic variable.
> I was squinting at the light curve and trying to get it to fit my
>    conception of Dyson-building, and I cannot get it to fit any
>    rational approach I can see. Of course, you can build megastructures
>    just for fun or according  to a random schedule.
> On 2016-08-06 04:46, Dan TheBookMan wrote:
> http://on.io9.com/1F00tSo
> Could it just be something rather mundane but rare to actually
>       see in such detail, such as the aftermath of a planet falling
>       into the star?

Dr Anders Sandberg
Future of Humanity Institute
Oxford Martin School
Oxford University

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