Quintuple Star System

[radtech497]

This popped up while I was constructing my mammoth reply...

What figure are you using for luminosities? http://arxiv.org/abs/1504.07065 gives temperatures, masses, and radii, which should allow calculating that, but I don't know how to derive them for the contact binary, since it only gives a common temperature for the two.

Do you have any additional information on orbit parameters or the like?

I used some figures from this paper instead; note in Table 8 there is some uncertainty about the smaller component of the contact binary pair's temperature: depending on whether or not a starspot was observed, the temperature might be as low as 4730K or as high as 4790K. Feeling a bit parsimonious, I split the difference and called it 4760K.

The same paper estimates the distance to the system to be 70 parsecs. The two components, according to the Simbad database, are separated by 1.86 seconds of arc, which at that distance works out to be 130.201 AU (19,477,722,574.314 km); this is an order of magnitude greater than the news reports, so take that with a moon-sized grain of salt.

Radtech497

[TSSL]

Ooh, thanks. That looks like a good source to have on hand.

Last night in bed, as I was drifting off to sleep, I kept obsessing over this system and had a couple more thoughts, which started out reasonable and got increasingly dream-like.

On the serious side, one potential big effect could be any presence by prehistoric xenosophonts. They could've xenoterraformed a planet, maybe allowing the main world of the contact system to be rather more hospitable. Looking around the EG, the best candidates for visiting xenosophonts are these guys: http://www.orionsarm.com/eg-article/4a646e52ca80b , who might've put life on one of the colder worlds a couple billion years ago, or http://www.orionsarm.com/eg-article/4b6d2e7446c5a , who could've been present 196 million years ago. Or there could be a more local xenosophont that isn't in the timeline. There could even have been a Muuh outpost, like even the Solar System apparently had, though not one that would've been discovered until more recently.

I was nearly asleep when I had the other thoughts, which was that the system could have an outpost from the Hogwarts School of Witchcraft and Wizardry. Let's not do that.

[TSSL]

I realized there's another culture with five sun gods: the Aztecs! (Granted, in their case four of them were ex-sun gods. There's a sequence.) Not sure who'd be who, but we could name the suns Tezcatlipoca, Quetzalcoatl, Tlaloc, Chalchiutlicue and Tonatiuh. These do not appear to have been used before.

I also am wondering if another possible prehistoric xenosophont which could've been present instead might be the Tunnelers? I'm not sure if they went into terraforming or not, but if they did stuff other than make big wormholes, perhaps they could fit.

[TSSL]

Say, how does one calculate blackbody temperatures for bodies in a multiple star system? I know that in single star systems, it's proportional to the fourth root of the star's luminosity. I'd suppose that a body that orbits two stars would use the fourth root of the sum of the stars' luminosities. But then how do we calculate the temperature contribution of the stars that the planet doesn't orbit?

[radtech497]

A method I have used is to first find the minimum distance separating the star from the planet, by taking the separation distance between the stars and subtracting the planet's apoastron distance (remembering to keep the distance in Astronomical Units). Then square that distance, take the inverse of that squared number, and multiply the inverse together with the luminosity of the star in question and the value of the Solar Constant (1361 or 1366 Watts per square meter, depending on which source you prefer). Then, divide that number (in W/m^2) by four, and multiply that by (1 - planetary albedo). Divide that number by 5.670373e-8, and finally, take the fourth root to find the equilibrium temperature in Kelvin.

If you, like me, want to also find a minimum contribution from that star, simply add the planet's apoastron distance to the distance separating the two stars, and repeat the above.

Hope this helps,

Radtech497

[TSSL]

Thanks I think that'll be very helpful, but my modosophont brain is having a little trouble keeping track of all the steps. Could you rewrite that as a formula with variables and numbers? Might be easier for me.

[radtech497]

To find the maximum contribution:
1) Find the separation distance between stars (in A.U.) minus the planet's apoastron distance from its star;
2) Square the result of #1, then take its inverse (1/x);
3) Multiply the result of #2 by:
3a) the luminosity of the non-host star, and
3b) then multiply that result by the Solar Constant;
4) Multiply the result of #3b by (1 minus the planet's albedo);
5) Divide the result of #4 by 5.670373 x 10 to the -8;
6) Take the fourth root of #5 to get the temperature in Kelvin.

To find the minimum contribution:
1) Find the separation distance between stars (in A.U.) plus the planet's apoastron distance from its star;
2) Repeat steps #2 through #6, as above.

Hope this works for you,

Radtech497

[TSSL]

Thanks! Sorry if I was a bit slow on the uptake, but the list definitely makes it easier to follow