Late Stages of Stellar Evolution
A ‘normal’ star is a massive sphere of gas, radiating energy that arises from nuclear fusion in its core. The star is stable because the gravitational forces trying to collapse the star are balanced by gas pressure due to the high temperatures inside the star. For most of its life, as a main sequence star, the star fuses hydrogen into helium. When hydrogen fuel runs low in the core the star must evolve, becoming a red giant - fusing helium into carbon as well as continuing to produce helium. More massive stars will briefly produce even heavier elements.
The final evolutionary state for a massive star may be a neutron star or a black hole, produced in a supernova explosion. A less massive star, such as the Sun, will end its life by briefly producing a planetary nebula as the core is exposed as a slowly cooling white dwarf star.
Current research areas
Wolf-Rayet Stars
Dramatic images taken in the infra-red reveal outflows from Wolf-Rayet stars, including stars in the Quintuplet cluster near the heart of the galaxy. The images, taken by Peter Tuthill, use optical interferometry on the Keck Telescope, currently the world's largest. See images and more information at Peter Tuthill's web page.
Red Giant Variables
Pulsating red giants and supergiants are observed using photometric, spectroscopic and interferometric techniques. These observations are compared with predictions of pulsation and dynamic atmospheric models to investigate fundamental properties of these stars -- stellar parameters, atmospheric structure, formation of dust particles, circumstellar features, .... Many of these properties are still poorly known.
For more information contact Dr Laszlo Kiss