Navigating Stellar Evolution: Unraveling the Time Dependence of the Habitable Zone

Abstract

The discovery of the first planet orbiting a main sequence star in 1995 by Michel Mayor and Didier Queloz, other than the Sun, revolutionized astronomy. Following this discovery, awarded with the Nobel Prize in Physics in 2019, planet-hunting became one of the most exciting disciplines in astrophysics, and new telescopes and instruments to more efficiently discover exoplanets were built. Thanks to these efforts, more than 5000 exoplanets are now known, and it can be estimated that, on average, the Milky Way contains more than one planet per star. The vast majority of these planets have been discovered around Sun-like main-sequence stars. This means that most planetary systems discovered so far will be affected by the evolution of their host star into a white dwarf. During the metamorphosis of a Sun-like star into a white dwarf, the conditions for planets orbiting this star dramatically change, which, without any doubt, also affects their habitability. This work performs a comprehensive exploration of the evolution of the habitable zones around Sun-like main-sequence stars, focusing on the interplay of factors such as surface albedo variations or atmospheric reflection, as well as stellar temperatures and luminosities. The equilibrium temperature framework is used to estimate the location of the habitable zone, assuming black-body emission but also incorporating real white dwarf spectra. The evolution of the host star is calculated with the SSE code developed by Jarrod Hurley and collaborators, and, for comparison, the more accurate tracks provided by MESA developed by Bill Paxton and collaborators are also used. The thesis begins with a brief summary of the evolution of a Sun-like star.