It is a very old and nearly burnt out star which has lost most of its outer layers. Astronomers want to know just how old this star is and what happened to its outer layers.

This is difficult because it is normally impossible to see inside a star. Fortunately, the surfaces of a few stars, including the Sun, vibrate upwards and downwards. These vibrations can be analyzed by borrowing techniques from seismology, which uses earthquakes or man-made explosions to send signals through the earth's crust to measure its density.

Astronomers can measure the density inside some stars by measuring the speed of naturally-occurring vibrations. Each vibration probes a different layer of the star.

Over the coming weeks, an international team led by Professor Ulrich Heber of the University of Erlangen-Nuernberg, Germany, will use over fifteen different telescopes around the world to make over one hundred nights of observations of V338 Ser to learn about its internal structure.

The Multi-Site Spectroscopic Telescope is an international project. Drs. Simon Jeffery of the Armagh Observatory in Northern Ireland; Simon O'Toole of the University of Sydney, Australia, and Stephan Dreizler of the University of Tuebingen, Germany, lead three teams, each making a different type of observation.

The project will use telescopes ranging from 1 meter to 4 meters in diameter and located in over seven nations around the world, including Australia, China, South Africa, Italy, Spain, Chile and the USA. Over 26 astronomers will measure how much light the star emits and how fast the surface of the star is moving inwards and outwards.

The project is also being supported by The Whole Earth Telescope, another international project which uses light variations alone to make seismological studies of rapidly varying stars.

One reason for such a large campaign is that it takes a lot of telescope time to measure and resolve the very weak signals coming from the star. Daytime interruptions can make these signals impossible to untangle.

Using several telescopes around the world should ensure that the star never sets. Although the approach has been used before, this may be the first time that a global asteroseismology project has tried to measure both light and spectrum variations at the same time for any star apart from the Sun.

Simon Jeffery said, "This project represents the best opportunity yet to identify pulsation modes and do real asteroseimology of a star of this class. It will also lead to the development of a range of new techniques for studying the interiors of many other stars."

The first telescopes started taking data on Tuesday, May 14, and observations will continue until June 24.

Related websites:

The Armagh Observatory

Simon Jeffrey's page

The Whole Earth Telescope


[Contact: Dr. C. Simon Jeffery ]

21-May-2002