The most sensitive X-ray observatory ever built, known as XMM-Newton, is
now enabling scientists to study the hottest objects and most violent
events in the far reaches of the Universe.

UK astronomers played a major role in developing the instruments on this
giant telescope, and they are now seeing the benefits of their labours by
receiving remarkable new data on the normally invisible X-ray Universe.

Dr. Hilary Magee of University College London’s Mullard Space Science
Laboratory will be speaking to the UK National Astronomy Meeting in
Cambridge on Wednesday 4 April about her research with XMM-Newton into
the atmospheres of nearby stars.

Many of these stars show explosions, or flares, similar to those which
occur on the Sun which are believed to be caused by twisting of magnetic
fields embedded in the Sun’s outer atmosphere, or corona. “Although flares
on the Sun can have dramatic effects on the Earth, flares on other stars
can be hundreds of times more energetic,” said Dr. Magee.

“The instruments on XMM-Newton are so sensitive that we can now get data on
nearby stars which allows us to compare them with observations of the Sun,”
she added. “By studying the X-rays from these stars, we can learn a lot
about the temperatures and physical processes taking place on these stars.”

“A major question that needs to be addressed is whether the same mechanism
that produces solar flares can also produce the 100-times larger flares
seen in some stars,” she said.

Preliminary analysis of the XMM-Newton data has already revealed intriguing
differences between the Sun and a flaring star known as AB Dor. Although AB
Dor is a close neighbour to our Sun, only about 50 light years from Earth,
it is much younger (about 20-30 million years old) and much more active.
Flares on AB Dor have been known to reach temperatures as high as 100
million degrees.

In addition, XMM-Newton data show that the huge magnetic loops linked to
flares on AB Dor reach a height of about a third of the star’s radius,
compared to less than a tenth for the Sun.

XMM-Newton has also detected flares from all three components of the system
known as Castor, which contains three binary stars and makes up one of the
two bright naked-eye stars in the constellation of Gemini.

This complex star system is located about 50 light years away and was
observed by XMM-Newton for 25 hours. For one of these binary stars, known
as YY Gem, most active regions are found between latitudes of plus and
minus 50 degrees on each star, which is a much wider band than on the Sun.

“Clearly conditions on these stars are very different from those on the
Sun,” said Professor Keith Mason of MSSL. “By studying the explosions that
occur under extreme conditions on other stars, we hope to shed light on the
way our own Sun works.”


Dr. Hilary Magee

Solar Physics Group

Mullard Space Science Laboratory

University College London

Dorking, Surrey, RH5 6NT

Phone: +44 (0)1483-204178

Mobile phone: 0771 8178937




* ESA web site

* UK XMM-Newton Information Centre