Under a Crimson Sun

Prospects for Life in a Red Dwarf System

David S Stevenson, Springer, MultCo 576.839S8474U 2013

A book about the prospects of life on planets around M and L stars.

Spectral class, hot to cold: O B A F G K M L : Oh Be A Fine (Girl/Guy) Kiss My Lips

O through F are very big, bright, and fast burning. Probably evolving too rapidly for intelligent life to emerge.

There are twice as many K stars as G stars, and far more M's and L's - some of the L's may be too difficult to detect, or have not yet ignited in 14 billion years. Are the coldest too unenergetic to power aerobic oxygen-generating photosynthesis?

Less luminous stars last far longer - and planets can orbit closer in. Too close in, and they tide-lock one face towards the star.

• p043 nebula to massive star in 500KY
• p043 solar nebula 30MY
  • "There is ample evidence that the solar nebula was showered with radioactive isotopes of aluminum. Their daughter isotopes are found abundantly in certain types of primitive meteorites called chondrites. These can only have been produced in a nearby supernova, as these isotopes have half-lives too short to have been produced earlier in the lifetime of the pre-solar nebula.
• p52 "Principle among the short-lived isotopes is aluminum-26. This isotope of aluminum has a half-life of 770,000 years. ...the asteroids of our solar system contain ample evidence of inclusion and of heating by aluminum-26. Thus, unlikely and presumably rare though such a scenario sounds, it does appear that at least our planetary system was fortuitously placed to be blitzed and enriched by a nearby supernova.
• p77 0.1 Msun Proxima Centauri, 1.4 TY to 10% He3, hotter
  • 4.4 TY, 50% He3, 2500K, 0.1% Lsun
  • 5.7 TY 84% He3, 3450K, 0.5% Lsun
  • 6.1 TY 96% He3, 5800K, 1% Lsun
  • 6.3 TY dim to cold
• p126 Diana Valencia: higher gravitational field, thinner lithosphere, more effective subduction
• p134 Finite life for plate tectonics
• p166 tidelocked atmosphere ( Manoj Joshi U. East Anglia, Tim Merlis Princeton )
  • SSP (star side pole) low, highs at 45 degrees lows at equator, high at dark side pole
  • modified by coriolis force,
• p212 photosynthesis, efficiency peak at 400 and 680/700 nm, weak in between

Note Added 2019

By 2012, new data changed our understanding of solar system formation and SLR (short lived radionuclides) like ²⁶Al. Supernovae also produce a lot of ⁶⁰Fe (which decays into nickel) and that is nearly absent from Vesta-sourced meteorites. An alternative, championed by Nicolas Daupas of the Origins Laboratory at the University of Chicago, is formation of the solar system inside the shell around a Wolf-Rayet star, perhaps 10 parsecs away. Their 2012 paper describes their meteorite analysis, and their 2017 describes their model of triggered star formation.