Tiny Star's Clues to Climate Change (Forwarded)

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03 Feb 2006

Tiny Star's Clues to Climate Change

New investigations of a tiny star in the constellation of Pegasus have
provided a novel insight into the Sun and its potential impact on Earth.

An international team of astronomers, including scientists from the
University of St Andrews, have developed a new understanding of how
stars, including the Sun, generate their magnetic fields. The new
finding may help develop further understanding of how changes in the
magnetic field of the Sun impact on Earth's climate.

The researchers from France and Scotland made a crucial discovery when
studying a small cool star 20 light-years from the Sun. The researchers
used new methods to make the first magnetic map of the star, and found
that this star has a very simple magnetic field, much like that of the
Earth's.

They explained: "Studying magnetic fields of stars is a novel way of
studying the magnetic field of our Sun. Although it always looks the
same, the Sun is variable, and the changes in its magnetic field,
although small, appear to affect the Earth's climate. Scientists think
that a well-documented decrease in the Sun's magnetic activity is the
most probable cause of the Little Ice Age, the cool period that
prevailed on Earth from the 15th to the 18th century."

The star, named V374 Pegasi, lies about 20 light-years from the Sun, in
the constellation of Pegasus. Although it is one of the Sun's closest
stellar neighbours -- much nearer to us than most of the stars visible
in the night sky -- V374 Peg is more than 100 times too faint to see
with the unaided eye. It is an ultra-cool star, one-third of the size of
the Sun, with a surface temperature of only 2900 C, in contrast to the
Sun's 5500 C.

The researchers examined the magnetic field of the star using the most
powerful instrument worldwide for carrying out this kind of research,
currently attached to a telescope in Hawaii. The new instrument was
especially designed by the Observatoire Midi-Pyrenees in France for
observing and studying magnetic fields in stars other than the Sun, and
is the only instrument that can study magnetic field topologies of
small, faint stars such as V374 Peg, that are notoriously difficult to
observe in detail.

The researchers were surprised to discover that the star had a simple
form of magnetic field.

"Scientists had previously predicted that magnetic fields of such small,
cool stars should be more chaotic and less structured than those seen in
the Sun. The new observations show instead that the ultra-cool star V374
Pegasi has a very simple, organised global magnetic field structure
rather like that of the Earth. It came as a complete surprise to us,"
they explained.

Further investigations on similar stars may reveal more clues about the
Sun itself and its likely impact on Earth.

They said: "These changes of the Sun are attributed to long-term changes
of the magnetic field that the Sun produces in its interior, through a
mechanism which is not yet fully understood. But it's like trying to
understand a disease with only one patient. By studying the magnetic
diseases of other stars, we should develop new insights into the Sun's
behaviour."

The results are published in the 3 February 2006 issue of Science.

NOTE TO EDITORS:

Copies of the embargoed paper are available from the AAAS Office of
Public Programs, Tel: +1-202-326-6440.