The Nacreous Oughts

27 December 2011

Scheherazade--Kepler-22b a.k.a. KOI-87.01--is an 11.5 magnitude G5 star at a distance of 180 parsecs from Earth. The visual luminosity works out to be 0.609459723 times the Sun's. My best fit to the data given is a bolometric correction of -.12 (=G5.5) & a stellar temperature of 5550 K. Then the bolometric luminosity is 0.791671499 & the stellar radius works out as 0.971723097.

Even though the stellar mass is given as 0.97, i think 0.90 would be more normal. Nevertheless, using this mass & the planet's period of 289.8623 days, i come up with a semimajor axis of 0.848502651 AU. The derived planetary temperature would be 20.6 Celsius with the Earth's albedo (0.36) & greenhouse effect (38), but i prefer A= 0.4375 & Ge= 54 which makes it 29 Celsius on average (call Earth something like 15 C). Because the planet is certainly larger than the Earth--its radius is given as 2.38.

The mass & density are not yet known. It would not be unreasonable to place their bounds as 10.79 for 0.8 Earth's density & 16.18 for 1.2. The gravity becomes 1.9 to 2.9 (not so habitable!). Two important considerations at this point. If it is more than 2.31 times Earth's escape velocity (at this temperature) it would keep hydrogen gas & presumably not support an oxidizing atmosphere. This artificial limit occurs at any density greater than 0.9439. I would find the heavier density more likely to my mind, except that the star is metal poor (log Fe/H= -0.29) & thus its planets are potentially less dense than they would be otherwise.

Finally, i estimate its rotation period, due to tidal braking, at 3 or 4 days; making the ratio of revolution-to-rotation periods an integral 105 gives a "day" on Scheherazade as 66 hours long.

This page is powered by Blogger. Isn't yours?