The Nacreous Oughts

16 January 2018


I finally got around to running the numbers for the planet of Ross 128, aka FI Virginis, Gliese 447, & Hip 57548. Using the Hipparcos parallax (".29958) & Visual magnitude (11.12) rather than those used by the discoverers (".29580 & 11.15) i get a visual luminosity of 0.0003459189604 or 1/2891. Since they go ahead & give the stellar mass & radius as 0.168 & 0.1967, i'm going to go with those, which means that for the effective temperature of the M4.5 star of 3192 K, the Bolometric Correction they used was 2.53.

So the total luminosity of the star is 0.003556103292 (1/281). For an orbital period of 9.9 days (1/37), the semimajor axis is 0.049788383 AU (4.6 million miles). The mass is given as 1.35 Earth's (131/97). There are two kinds of assumptions one can make for a nearly Earth-sized planet: the density increases gradually with the mass, or the density is somehow related to the stellar metallicity (here: 0.955 the Sun's). On the first assumption, this planet comes out at around 8573 miles in diameter (MINIMUM)--79/73, its gravity is about 15% greater than Earth's (137/119), & its escape velocity is about 12% higher. Alternately, Josaphat might be 8852 miles in diameter, with 1.08 gravity & 1.1 Ve.

For combinations of Albedo & Greenhouse effect of 0.19/20 to 0.51/60, the average surface temperature works out at from 37 to 43 C. Or, say, 25 degrees warmer than Earth.


Labels: ,

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