Low-mass main-sequence stars like our Sun are continuous sources of outflowing hot magnetised plasma. In the case of the Sun, this is known as the solar wind, whereas for other stars they are... Show moreLow-mass main-sequence stars like our Sun are continuous sources of outflowing hot magnetised plasma. In the case of the Sun, this is known as the solar wind, whereas for other stars they are called stellar winds. These types of stars comprise 93% of all stars in our galaxy, and also host the bulk of all exoplanets discovered to date. Therefore, understanding their wind outflows and how they interact with the planets they host is crucial to assessing the long-term evolution of planetary atmospheres, which in turn determines their potential to support life as we know it. The interactions between stellar winds and planets can also produce signals which could be detected with current-generation telescopes.Current measurements of the winds of low-mass main-sequence stars are limited, and have only been successful in a handful of cases. However, by coupling state-of-the-art magnetohydrodynamic (MHD) models of stellar winds with observational constraints, 3-dimensional snapshots of the wind environments around planet-hosting stars can be obtained. In this thesis, I utilise such models to explore the winds of these stars, and predict the potentially-observable signatures that may arise from their interactions with orbiting planets. Show less
This thesis focus on the interaction between M dwarf stellar winds and Galactic cosmic rays and the possible effects on the habitability of exoplanets. We use numerical simulations to describe the... Show moreThis thesis focus on the interaction between M dwarf stellar winds and Galactic cosmic rays and the possible effects on the habitability of exoplanets. We use numerical simulations to describe the stellar winds of M dwarfs using observable constraints, such as the mass-loss rate, X-ray luminosity, and magnetic field strength/flux. Additionally, we use numerical simulations to describe the propagation of Galactic cosmic rays within M dwarf planetary systems. With these simulations, we can calculate the flux of Galactic cosmic rays reaching exoplanet magnetospheres/atmospheres. Measuring cosmic ray fluxes in exoplanet atmospheres is yet not possible, but cosmic rays are an important ingredient in the context of planetary habitability. For this reason, quantifying these fluxes is essential to complete the habitability “puzzle”. Future exoplanet atmosphere observations with space telescopes, such as the JWST and the ARIEL, will enable us to constrain cosmic ray fluxes in exoplanet atmospheres. Show less
Red Dwarfs are at the heart of Astronomy because they are the most abundant type of star that we know of in our Galaxy. Yet, surprisingly little is known about their formation, evolution and the... Show moreRed Dwarfs are at the heart of Astronomy because they are the most abundant type of star that we know of in our Galaxy. Yet, surprisingly little is known about their formation, evolution and the nature of their companions. In this thesis I present the first results of the WFCAM Transit Survey, a unique long-time monitoring program of many thousands of red dwarfs in the infrared, where they are the brightest. By studying their properties in eclipsing binary systems it is shown that red dwarfs are of great value to simulations of low-mass star formation, binary dynamics, stellar structure and ultimately the fundamental properties of Earth-like planets. Show less
