Astronomy at St Andrews 2021 - 2024

The St Andrews astronomy group is interested in questions of origins: where do galaxies, stars and planets come from, and what fundamental physics explains their formation? How widespread is life and how did it arise on Earth and on other worlds? We are world leaders in solving intricate mathematical problems, and we use novel methods such as observations at very high precision and simulations with super computers.

We are joined by other groups across Scotland via the Scottish Universities Physics Alliance (SUPA), and internationally, in searching for hot and cool Earth-sized planets, homing in on habitable worlds where life could exist, and developing ways to detect life on those distant worlds.

Our investigations span a wide range of size scales, from discovering planetary systems around stars a few light years away to measuring the force of gravity acting on the whole universe. We discover hot extra-solar planets by using robotic wide-angle cameras and NASA's TESS space telescope to monitor thousands of stars and find those that briefly dim each time an orbiting planet passes in front of its parent star. We measure accurate

sizes for these planets by observing the transit light curves using ESA's CHEOPS space telescope, and determine the planet masses using the high-precision HARPS spectrographs to measure how much the orbiting planet wobbles its host star.

We discover cooler and smaller more Earth-like planets by using a global network of robotic telescopes to watch gravitational lenses, exploiting Einstein's prediction that a planet drifting across the sightline to a distant background star bends its light. We learn about how planets form by studying the light from the gas and dust grains that accumulate to form planets, comparing with our computer simulations to understand the chemistry may lead to formation of biological molecules.

Young stars have strong magnetic fields that interact with orbiting planets and their own magnetic fields. We study the signatures of this

interaction to understand how planets form and evolve. We investigate the physics of mineral clouds and lightning in the atmospheres of cool brown dwarf stars and extrasolar planets, processes that may play a role in the origin of life. We compare observations and computer simulations to study how stars form in galaxies and how feedback from young stars drives a dynamic, bubbling interstellar medium, the dusty gas from which new stars are born.

We include energetic supernova explosions when massive stars die and the ionising radiation from massive stars that heats the gas in the galaxy to temperatures above than 10,000 degrees Centigrade.

On galaxy and cosmological scales, we measure how gas and stars move within galaxies to study how galaxies form their characteristic shapes of flat discs, spiral arms and central bulges, and how these change as galaxies collide and merge to grow larger elliptical galaxies. We study the supermassive black holes that lurk in galaxy cores, to understand how they form and grow, and how their huge output of energy and radiation affects the host galaxy evolution.

We study how gravity works both within galaxies and across the wider universe. Stars orbit in galaxies so fast that there appears to be too little mass to hold galaxies together, and our expanding universe appears to be accelerating. We understand gravity well enough to send space probes to other planets, but to understand these larger scale puzzles we investigate alternatives to current ideas of Dark Matter and Dark Energy, comparing our predictions with observations to test how gravity works.