Publicação
The Impact of Stellar Activity on the Planetary Habitability
| Resumo: | In 1995, Michel Mayor and Didier Queloz made history by discovering the first exoplanet around a solar-like star. Their groundbreaking achievement eventually earned them the Nobel Prize in Physics in 2019, 24 years later. Since the 1990s, the number of known exoplanets has grown to over 5000. This discovery surge has sparked considerable interest in life outside Earth, prompting numerous studies to address the age-old question, "Are we alone in the Cosmos?". Astrophysicists have been striving to come closer to finding an answer by employing various technologies, including the development of telescopes like the space-based Kepler telescope, dedicated to detecting and studying exoplanets and their potential habitability within the habitable zone.The habitable zone is the region around a star where a rocky planet could have liquid water on its surface. However, the conventional definition of the habitable zone does not consider the effects of stellar rotation and magnetic activity on a planet's habitability. Understanding rotation and stellar activity is crucial in this context. As a result, this study aimes to investigate the impact of stellar rotation and magnetic activity on the habitability of exoplanets.This study encompasses two distinct components: observational and theoretical. The observational component focus on the analysis of light curves of approximately 2000 stars obtained through data collected by the Kepler satellite. The chosen sample exclusively comprises KOIs (Kepler Objects of Interest), specifically focusing on those linked to multiple planetary systems and single systems with one candidate planet. Calibration and correction techniques were employed to ensure the accuracy of the data, providing insights into the observed stars' rotation period and magnetic activity.The theoretical component delves into creating two distinct stellar evolution models for each star that exhibited rotational modulation (a total of 332 stars). One model considers rotation, while the second disregards any rotational effects. The significance of stellar activity in the habitable zone is obtained by comparing the results from these two models. When categorising stars based on effective temperature, those with higher S_ph (photometric magnetic activity proxy) had a more pronounced impact on the habitable zone compared to those with lower S_ph. Regardless of S_ph values, the fastest-rotating stars are associated with the most significant impact on the habitable zone. Incorporating rotation into the models results in habitable zone limits moving closer to the host star and narrowing the habitable zone. For the solar system, these values correspond to a variation of approximately 2.31% for HZI (inner habitable zone), 1.49% for HZE (exterior habitable zone), and 0.55% for HZW (habitable zone width). The inner and outer habitable zone limits impact exhibited a polynomial relationship, with the inner habitable zone being more significantly affected by stellar rotation and magnetic activity.Both stellar rotation and their relation with magnetic activity significantly influence the boundaries and characteristics of the habitable zone. While their impact may not be readily apparent when considering the conventional habitable zone definition alone, it is crucial to consider magnetic activity in the search for life. This is particularly important due to the effects of space weather, which were not considered in this work. |
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| Autores principais: | Lapa, Gabriela Santos |
| Assunto: | stars: rotation stars: activity stars: starspots stars: evolution techniques: photometric estrelas: rotação estrelas: atividade manchas estelares estrelas: evolução técnicas: fotométricas |
| Ano: | 2023 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade de Coimbra |
| Idioma: | inglês |
| Origem: | Estudo Geral - Universidade de Coimbra |
| Resumo: | In 1995, Michel Mayor and Didier Queloz made history by discovering the first exoplanet around a solar-like star. Their groundbreaking achievement eventually earned them the Nobel Prize in Physics in 2019, 24 years later. Since the 1990s, the number of known exoplanets has grown to over 5000. This discovery surge has sparked considerable interest in life outside Earth, prompting numerous studies to address the age-old question, "Are we alone in the Cosmos?". Astrophysicists have been striving to come closer to finding an answer by employing various technologies, including the development of telescopes like the space-based Kepler telescope, dedicated to detecting and studying exoplanets and their potential habitability within the habitable zone.The habitable zone is the region around a star where a rocky planet could have liquid water on its surface. However, the conventional definition of the habitable zone does not consider the effects of stellar rotation and magnetic activity on a planet's habitability. Understanding rotation and stellar activity is crucial in this context. As a result, this study aimes to investigate the impact of stellar rotation and magnetic activity on the habitability of exoplanets.This study encompasses two distinct components: observational and theoretical. The observational component focus on the analysis of light curves of approximately 2000 stars obtained through data collected by the Kepler satellite. The chosen sample exclusively comprises KOIs (Kepler Objects of Interest), specifically focusing on those linked to multiple planetary systems and single systems with one candidate planet. Calibration and correction techniques were employed to ensure the accuracy of the data, providing insights into the observed stars' rotation period and magnetic activity.The theoretical component delves into creating two distinct stellar evolution models for each star that exhibited rotational modulation (a total of 332 stars). One model considers rotation, while the second disregards any rotational effects. The significance of stellar activity in the habitable zone is obtained by comparing the results from these two models. When categorising stars based on effective temperature, those with higher S_ph (photometric magnetic activity proxy) had a more pronounced impact on the habitable zone compared to those with lower S_ph. Regardless of S_ph values, the fastest-rotating stars are associated with the most significant impact on the habitable zone. Incorporating rotation into the models results in habitable zone limits moving closer to the host star and narrowing the habitable zone. For the solar system, these values correspond to a variation of approximately 2.31% for HZI (inner habitable zone), 1.49% for HZE (exterior habitable zone), and 0.55% for HZW (habitable zone width). The inner and outer habitable zone limits impact exhibited a polynomial relationship, with the inner habitable zone being more significantly affected by stellar rotation and magnetic activity.Both stellar rotation and their relation with magnetic activity significantly influence the boundaries and characteristics of the habitable zone. While their impact may not be readily apparent when considering the conventional habitable zone definition alone, it is crucial to consider magnetic activity in the search for life. This is particularly important due to the effects of space weather, which were not considered in this work. |
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