Public Lectures for the Session 2004-2005 held in Room F14 of the Renold Building, University of Manchester.
Delivered to the Manchester Astronomical Society

20 January 2005

''The Life of Stars''

Dr. Myfanwy Bryce
(Jodrell Bank Observatory, University of Manchester)

Dr. Bryce thanked the Society for her invitation to present this lecture. She began with a brief description of the diagrams used to describe various types of stars. The model commonly used by astronomers to classify stars is the Russell-Hertzsprung diagram. In 1910 Ejnar Hertzsprung and Henry Russell independently conceived the diagram.

Stars are depicted in groups on the diagram and these groupings are called "Sequences". The central section of the diagram is the area here our Sun resides as a main sequence member. During this time on the main sequence, stars spend most of their life burning hydrogen and a little helium.

As the Sun evolves it travels across the diagram. Our Sun started life in a molecular cloud, developed a rotating disk and produced jets as a proto-star and then developed into a yellow dwarf. It will eventually grow into a red giant and probably evolve into a planetary nebula.

Stars are produced in dense nebulae, often obscured from view by dust. One star formation region is the Eagle Nebula. If we look deep into the Eagle Nebula small finger-like filaments are at the heart of producing stars.

For Sun sized tars it has recently been shown that gravity just manages to form a star in a molecular cloud. Dr. Bryce then gave a brief description of the types of stars that have been studied. Taf Tauri type stars shed enormous amounts of matter which is thrown out a collimated outflows. These types of stars are typically young. New stars forming have been recently discovered in their "switching on" phase. Places like The Trapezium in Orion region are very good stellar nurseries.

As the Sun evolves it will move through the main sequence and move to a different part of the Hertzsprung-Russell diagram. When all hydrogen in the core has been converted to helium the nuclear fusion ends. It is at this point that a Red Giant is formed. The Star undergoes a major change in its structure. Betelgeuse is a huge red giant. The Sun is predicted to produce a smaller atmosphere which won't reach the Earth, and won't expand to be as previously thought.

Synopsis by Sotira Trifourki (Secretary)

Maintained by Michael Oates
Page modified 28 October, 2006