Optical observations

Optical photometry and spectroscopy

Optical observations of stars in young open clusters are important for a number of reasons. Firstly, it is not always obvious which stars are members of the cluster and which are background objects. Photometry and spectroscopy can help by determining positions on the Hertzprung-Russell diagram and radial velocities.

Becuase the cool, low-mass members of the clusters are faint then large telescope like the William Herschel Telescope and the Anglo Australian Telescope are used to obtain high resolution spectroscopy. From these spectra, taken with echelle spectrographs, one can obtain projected rotation velocities, radial velocities, chemical abundances (especially lithium) and chromospheric activity measures. By observing clusters with different ages and compositions it is then possible to piece together the history of angular momentum loss, magnetic activity and photospheric lithium depletion, in a star like the sun.

Further observatory and telescope links

+ Anglo Australian Observatory.
+ Cerro Tololo Interamerican Observatory.
+ Isaac Newton Group of Telescopes.
+ South African Astronomical Observatory.
Rob Jeffries rdj@astro.keele.ac.uk
Department of Physics
University of Keele
Keele
Staffordshire ST5 5BG, UK
3rd December 1996