"And in fact there is some value in keeping distinct different views of history without collapsing them into one another, and I think this tension can be healthy rather than unhealthy." Edward W Said

(via barewalls dot com)

"The double dawn had risen; the orange sun overpowered the wan light of the blue sun..." Kameron Hurley, God's War (2011)

From the descriptions in the book, the planet Umayma orbits either zeta Aurigae itself, or else another "Zeta Aurigae System"; obviously i am choosing to go with the former, since images of this star have been repeatedly attempted since the days of Chesley Bonestell. Curiously it has two other names which are never used in sci-fi OR astronomy as far as i can tell: Haedus I. & Azaleh. "Haedus I." affects my imagination differently from "Azaleh", & "Zeta Aurigae" differently still. Additionally, it is designated as HD 32068 & HIP 23453.

Hipparcos gives the parallax as ".00414, which works out to 787 light years (somewhat greater distances are also mentioned). I am going to use a visual magnitude of 3.751 & the interstellar absorption 0.25 mag as adopted by Bennett (1996), although not all of my calculations square with his in the end. His visual magnitude difference between the two stars, 2.22, gives a visual luminosity of 2021.153591 combined, with the orange star 1789.550684 & the blue star 231.6029066.

Many of the models i've looked at end up with a bolometric correction rather in excess of the scales i am used to seeing for cool supergiants. So i wiill take the observed diameter, ".0055 which works out to 142.8 times our Sun. Then the best fit seems to be around T= 3825 K, BC -0.83 & bolometric luminosity of 3857.182597 (nearer to gK2 than the K3 or K4 usually given). Then, i'm taking the secondary as 13000K & Bc -0.64 (B7), so that its bolometric luminosity equals 417.5841494 & its radius would be 4.067628534.

An earthlike planet might orbit the twin suns at a distance of 154 AU. If their combined mass is 10.6 solar, its orbital period becomes 590 years. From this distance the large star would seem to be nearly as large as our own sun seen from Earth; they would spread apart as widely as three times its diameter during the 2.7 year binary period. There are about 220 of these stellar revolutions in one planetary "year".

--------------------------------------------------------------------------------------------------- (12/14) According to my revised calculations, the semimajor axis of a habitable planet would be more like 65.69837451 AU, & the derived orbital period would be 163.5607164 years, or around 61.45 times the double stars' revolution period. Making that an even ratio of 61, the planet would orbit at 65.37560877 AU in 162.3568761 years. The apparent size of A would be 2.18, & the planet would roughly correspond to the sixth from the suns--although at least the first one, at 4 AU, is likely to be unstable in its orbit.

Labels: #astronomy