Abiogenesis Zones around Active M-Dwarfs
Friday 6 July, 11:50
It is likely that the building blocks of life were formed photochemically from hydrogen cyanide on the surface of the Early Earth. To answer whether this same chemistry can happen on planets around different stars, we compare the rates to form sugars in the presence of the UV light, and the rates at which inert adducts form in the dark. We have found that the sun and other stars, down to K5V, provide sufficient light to form life's building blocks, and habitable zone planets orbiting these stars can be said to lie within that star's 'abiogenesis zone'. Quiet M-dwarfs, at any evolutionary stage, would not produce enough UV light to initiate this synthesis.
Sufficiently active M dwarfs, on the other hand, with flares of energy greater than 5x1034 erg with frequency greater than than once every 50 days, would provide enough energy to drive the formation of sugars. We are most interested in planets on which life started long ago, since it is unlikely we will be able to detect life that has just begun on an exoplanetary surface. Therefore it is important to have a good understanding of how flare rates change with stellar age.
I will discuss the experimental, theoretical and observational work done to demonstrate the efficiency of prebiotic photochemistry on M-dwarfs, and the work we have just undertaken with flare statistics on M-dwarfs, determining how many active M-dwarfs may be able to bring about this synthesis by flaring, as a function of stellar age.