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Armagh Astronomers to observe Ringing Star with Global Telescope

Over the coming weeks an international team, including Simon Jeffery, Vincent Woolf and Amir Ahmad of the Armagh Observatory, will use over fifteen different telescopes to make over one hundred nights of observations of just one star to learn about its internal structure.

V338 Ser The constellation of the "Serpent" contains a variable star, called V338 Ser, which vibrates with several periods of about ten minutes. It is a very old burnt out star which seems to have lost its outer layers. Astronomers want to know just how old this star is and how much of its outer layers have been lost.

This is very 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.

The Multi-Site Spectroscopic Telescope represents an international project led by Professor Ulrich Heber, from Bamberg, Germany. Dr Simon Jeffery of the Armagh Observatory leads one of three project teams. The project will use over fifteen different telescopes ranging from 1 metre to 4 metres 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. From Armagh, Dr Vincent Woolf will travel to the European Southern Observatory in Chile and Mr Amir Ahmad will observe from the Isaac Newton Group of Telescopes on La Palma in the Canary Islands. Drs Simon Jeffery and Don Pollacco (of Queen's University Belfast) will coordinate some of the data analysis as the observations are being made.

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 asteroseismology of a star of this class. It will also lead to the development of a whole range of new techniques for studying the interiors of many other stars."

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

Contact: Dr Simon Jeffery

Last Revised: 2002 May 15th
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