(via space dot com)

So Proxima has a planet... Also known as Gliese 551 & HIP 70890, this dim red flare star (according to the paper, visual magnitude 11.05 at 1.295 parsecs--for a parallax of "0.7722, although Hipparcos gives 0.77233--), which is probably (but not certainly?) coeval with Alpha Centauri, with spectral type M5.5 V (3054 K), stellar mass 0.118 ⊙ (2/17) and observed radius 0.1410 (or 1/7th ⊙), appears to have a planet of at least 1.27 (about 52/41) ⊕ in a close, 11.186 (1/33 y.)-day orbit.

This works out to 0.048011508 or 1/21 AU, which for a visual luminosity of 0.00005553162797 (1/18008) & bolometric (BC at -3.60) 0.001528278072 (1/654), makes for a blackbody temperature of 252.3673234 of the planet. If its albedo & greenhouse effect are like the Earth's (0.36, 38K) then its average surface temperature is -9° C; if a little larger (say, 0.60 & 80), an average of 8° C is possible.

According to Li Zeng, a rocky planet with this mass should be about 1.083159015 (13/12) ⊕ in diameter (=8576 miles), & have a surface gravity of 1.083247851 ⊕ (at about the same density; a greater density is possible).

I call it "Hercolubus" because a cloud covered world of a star this cool would be red to our eyes. (Its inhabitants might be Hercolubozos.) --Certainly not Ad Astra or Furon...or even Meton. Discussions of its potential climates.

Though much has been said about this "red" sun, it is much bluer than candlelight (1400K); its energy is about 53% of our sun's & i would expect a leaf running on the same chemistry to be about twice as large as its Terran equivalent. Illumination-wise, the day would seem about 2% of ours (2/83), or about the same as a point in orbit between Jupiter & Saturn--brighter than "Pluto Time," at any rate.

Clocks are supreme on Hercolubus.

(Prague Astronomical Clock, via the aussie nomad dot com)

Labels: #exoplanets, #proxima