Galactic Astronomy at the University of Hertfordshire

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The Milky Way is our home galaxy. It is accompanied by smaller satellite galaxies, the most important ones are the Large and Small Magellanic Clouds. The evolution of galaxies is closely linked to the evolution of the stars they contain. The matter in galaxies in the form of gas is the raw material for the formation of stars and planetary systems. Our group investigates the first stars born in the Milky Way over 10 billion years ago - a phase only directly observable now in very distant galaxies at high redshift. Also with a view to understanding what the young Milky Way was like, we study stars known as white dwarfs that are the extremely faint stellar remnants from these early days. Some white dwarfs reside in binaries, which are expected to be important sources of gravitational waves, and a few of them will eventually merge and explode as supernovae (another path way by which stars feed back into the chemistry and dynamics of interstellar matter). To solve problems in how stars age to become these stellar remnants, our group investigates stars passing through the preceding extreme red giant evolutionary phase, both in the Milky Way and the Magellanic Clouds -- this is the moment when stars return matter to the interstellar gas during a strong superwind phase. The returned gas is chemically enriched by nuclear fusion that has gone on inside the stars and will be re-cycled to form the next generation of stars. The Milky Way and its satellites are our only chance to have a close-up look at these processes. Long wavelength observations (made in the sub-mm and infrared) allow us to investigate the birth of stars and brown dwarfs. We are leading a new generation of surveys of our Milky Way Galaxy that are to designed to study the formation of stars from their initial condensation under gravity from vast clouds of cold gas to their emergence as stars powered by nuclear fusion reactions. The new surveys will detect hundreds of regions where stars are being formed, both in large clusters and in isolation. With this large dataset we can use a statistical approach to determine the different ways that stars can form in the Galaxy as a whole and the timescales involved in the process. We perform systematic radial velocity searches of nearby stars to discover planets and then follow some of these up with high resolution imaging and spectroscopy in order to discern their atmospheric properties. We especially target low mass stars both using Doppler Wobble and by looking for planets periodically eclipsing their parent star. During the period of the grant we expect to make the first detections of Earth-mass planets in the habitable zones of the closest stars. In addition we are identifying populations of nearby youthful M stars which we will target with existing and new high resolution facilities to open up potential to directly image the details of other Solar Systems at separations as small as that of the Earth to Sun distance. We also discover, follow-up and model the properties of the coolest failed stars (brown dwarfs) whose temperatures and properties offer substantial overlap with Solar System planets and insight into planets in orbit around other stars as well as on their own.