16 May 2002
Global Telescope to Observe Ringing Star
Over the coming weeks an international team, led by Professor Ulrich Heber
of the University Erlangen-Nuernberg, Germany, will use over fifteen
different telescopes around the world to make over one hundred nights of
observations of just one star to learn about its internal structure.
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 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.
The Multi-Site Spectroscopic Telescope represents an international project
led by Professor Ulrich Heber of the University of Erlangen-Nuernberg,
Germany. Drs Simon Jeffery of the Armagh Observatory, Northern Ireland,
Simon O'Toole of the University of Sydney, Australia, and Stefan Dreizler of
the University of Tuebingen, Germany lead three teams, each making a
different type of observation. 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. 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 asteroseismology 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 will start taking data on Tuesday 14th May, and
observations will continue until the 24th June.
Contact:
Dr C Simon Jeffery
Armagh Observatory, College Hill, Armagh BT61 9DG, Northern Ireland
email: csj@star.arm.ac.uk
tel: +44 28 3752 2928 ext. 25
mobile: +44 78 1062 8212
fax: +44 28 3752 7174
WWW: http://star.arm.ac.uk/~csj/
Notes:
1. The project team comprises:
Ulrich Heber, Bamberg Observatory, Germany
Simon Jeffery, Armagh Observatory, UK
Simon O'Toole, University of Sydney, Australia
Stefan Dreizler, Universität Tübingen, Germany
Sonja Schuh, Universität Tübingen, Germany
Vincent Woolf, Armagh Observatory, UK
Siggi Falter, Bamberg Observatory, Germany
Oliver-Mark Cordes, Universität Bonn, Germany
Darragh O'Donoghue, SAAO, South Africa
Ilidio Lopes, Oxford, UK, and Instituto Superior Tecnico, Portugal
Don Pollacco, Queens University Belfast, UK
Roberto Silvotti, University of Naples, Italy
Silvia Marinoni, Bologna University, Italy
Roy Oestensen, Isaac Newton Group, La Palma,
Malvina Billeres, European Southern Observatory
Betsy Green, Steward Observatory, Az, USA
Mike Reed, Iowa State University, USA
Atsuko Nitta, Apache Point, NM, USA
Scot Kleinman, Apache Point, NM, USA
Jurek Krzesinski, Apache Point, NM, USA
Hans Kjeldsen, Teoretisk Astrofysik Center, Aarhus, Denmark
Stephane Charpinet, Observatoire Midi-Pyrenees, France
Richard Townsend, University College, London, UK
Jiang Xiaojun, Beijing Astronomical Observatory, China
Noella D'Cruz, University of Sydney, Australia
Andrew Jacob, University of Sydney, Australia
Amir Ahmad, Armagh Observatory, UK
and The Whole Earth Telescope collaboration
2. Telescopes used by the project include:
Calar Alto Observatory 3.5m, Spain
European Southern Observatory, New Technology Telescope 3.5m, Chile
Apache Point Observatory 3.5m, New Mexico, USA
Mount Stromlo and Siding Springs Observatory 2.3m, Australia
La Palma Observatory, Nordic Optical Telescope 2.5m, La Palma, Spain
European Southern Observatory, Danish Telescope 1.5m, Chile
Steward Observatory, Bok Telescope 2.3m, Arizona, USA
Mount Stromlo and Siding Springs Observatory 1.0m, Australia
Beijing Observatory 0.85m, China
South African Astronomical Observatory 1.0m,, South Africa
Loiano Observatory 1.5m, Italy
Calar Alto Observatory 2.2m, Spain
La Palma Observatory, Jacobus Kapteyn Telescope 1.0m,
Isaac Newton Group, La Palma, Spain
Erwin Fick Observatory, Mather Telescope 0.60m, Iowa, USA
McDonald Observatory 2.1m, Texas, USA
and other telescopes in The Whole Earth Telescope collaboration
3. Information about the Whole Earth Telescope collaboration may be
found on the WWW at: http://wet.iitap.iastate.edu/