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RAS PN 07/17 (NAM 13): WHERE IS THE GAS IN INTERSTELLAR SPACE?

Last Updated on Wednesday, 07 April 2010 18:15
Published on Tuesday, 17 April 2007 00:00
A team of astronomers led by Professor Martin Barstow of the University of
Leicester have searched for the hot gas thought to be present in the interstellar space around the Sun but found it just isn’t there.
Speaking at the Royal Astronomical Society National Astronomy Meeting in Preston on Tuesday 17 April, Professor Barstow will present a map of the local interstellar medium, the gas lying between the stars out to distances of about 300 light years from the Sun, made using the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite.
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Anita Heward
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WHERE IS THE GAS IN INTERSTELLAR SPACE?
A team of astronomers led by Professor Martin Barstow of the University of
Leicester have searched for the hot gas thought to be present in the interstellar space around the Sun but found it just isn’t there.
Speaking at the Royal Astronomical Society National Astronomy Meeting in Preston on Tuesday 17 April, Professor Barstow will present a map of the local interstellar medium, the gas lying between the stars out to distances of about 300 light years from the Sun, made using the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite.
Professor Barstow and his team used FUSE to observe a group of white dwarf stars (compact remnants of stars like our Sun will be at the end of its life). The scientists intended to probe the structure of interstellar space in the vicinity of the Sun by searching for the imprint of oxygen in the ultraviolet light from the stars. However, all the oxygen detected was found to be in the atmospheres of the stars and no interstellar oxygen was found. This implies that, rather than being full of tenuous ionized gas, as expected, this region of interstellar space (the Local Cavity) is actually empty and was probably swept clear by an ancient supernova explosion a few million years ago.
Our present picture of the local interstellar medium is that the Sun and Solar system are embedded in and near the edge of a wispy diffuse cloud, known as the Local Cloud (or Local Fluff). This cloud, which is only 20-30 light years across, is itself in a larger much less dense region called the Local Bubble or Local Cavity.
The gas in the Local Cavity was expected to bear the scars of recent nearby events, such as supernova explosions, and radiation from hot young stars. These would make the cavity gas hot and ionized, with the electrons stripped from the constituent atoms, and should be detected by FUSE. The hot gas should emit also X-rays that are detected as a diffuse background in X-ray telescopes. However, if there is no hot gas present, then we need to find another explanation for this X-ray background. One novel suggestion is that it arises from the exchange of charged particles at the boundary between the Sun’s magnetic field and interstellar space.
CONTACT:

Professor Martin Barstow
University of Leicester
Tel:  +44 (0)116 252 3492
On 17 and 19 April, Professor Barstow can be contacted via the NAM press office (see above).
NOTES FOR EDITORS

The 2007 RAS National Astronomy Meeting is hosted by the University of Central Lancashire. It is sponsored by the Royal Astronomical Society and the UK Science and Technology Facilities Council.
This year the NAM is being held together with the UK Solar Physics (UKSP) and Magnetosphere, Ionosphere and Solar-Terrestrial (MIST) spring meetings. 2007 is International Heliophysical Year.
The FUSE satellite was launched on 24 June 1999 and is a collaboration between NASA and other space agencies.
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