Free Astronomy Magazine September-October 2021

13 SEPTEMBER-OCTOBER 2021 ASTRO PUBLISHING oxygen. The model allows different parameters to be varied, showing how initial settings can affect the amount of oxygen produced by photosynthetic life. Curiously, the most interesting results came when the team modeled the orbital obliq- uity (or the inclination of the rota- tion axis) of a virtual planet. Average values of this parameter lead in the oceans to an optimal production of oxygen (which is then transferred to the atmosphere) and nutrients for the sustenance of life. A lmost half a century ago, the creators of Star Wars imagined a life-sustaining planet, Tatooine, orbiting a pair of stars. Now, scientists have found new evi- dence that five known systems with multiple stars, Kepler-34, -35, -38, -64 and -413, are possible candidates for supporting life. On the contrary, very low or very high values of the rotation axis in- clination seem to limit the prolifer- ation of life. The 23.5 degree inclination of the Earth’s axis seems to be a confirmation of the validity of this latest study (the tilt of the axis varies between 22.1 and 24.5 degrees, during a cycle that aver- ages about 40,000 years). If confirmed, orbital obliquity be- comes yet a further constraint in the search for complex life on other planets, adding to astronomers the difficulty of having to now derive the rotation axis inclination of an observed exoplanet before adding it to the candidate list. !