Could Alien Life Cope with a Hotter, Brighter Star?

The stars in the night sky shine in myriad hues and brightnesses—piercing blues, clean whites, smoldering crimsons. Every star has a different mass, the basic characteristic that determines its size, lifespan, light output and temperature (which we discern as a particular color).

Yet when it comes to the existence of life, we know with certainty of only a single star—a toasty, yellow-whitish one, our Sun—that has permitted the rise of life on an encircling world. Astrobiologists are quite convinced, though, that life can also develop on planets orbiting smaller, cooler stars.

But what about stars with light more intense than our Sun's? A new paper, accepted for publication in the International Journal of Astrobiology in May, examines some of the fundamentals for life arising around a class of slightly heftier, hotter stars known as F-type main-sequence stars. (Stars in the main-sequence are in "full bloom," so to speak, and like our Sun, fuse hydrogen into helium in their cores.) Procyon, a bright white star and the brightest star in the constellation Canis Minor, is a well-known F-type main-sequence star. These bigger cousins to the Sun differ from our home star in many important ways when it comes to astrobiology.

The new study specifically considers how the higher levels of ultraviolet (UV) radiation cranked out by F-type stars could hinder the development of alien life. UV rays can alter or destroy the molecules, such as DNA, that are deemed necessary for carbon-based biochemistry. Another drawback of F-type stars, as the study conveys, is that they live shorter lives than slower-burning stars like the Sun as well as orange (K-type) and red dwarf (M-type) stars. This variable is important because life, as we understand it, needs a lot of time to get going and to eventually evolve complexity. Furthermore, the more massive a star is, the rarer it is; tiny M-type stars vastly outnumber G-type stars, which in turn outnumber heavier F-type stars.