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Sending astronauts to reignite the Sun, the premise of sci-fi feature Sunshine, is the least of our problems when we are currently faced with global warming, global terrorism, and global economic collapse. Nevertheless, astronomers are concerned about recent findings regarding the hot gas surrounding our star and its stellar neighbours. Put simply they cannot find these hot gases. A team of astronomers led by Martin Barstow of the University of Leicester, UK, has used data from the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite to map the local interstellar medium to a distance of 300 light years. They reported details of their observations to the Royal Astronomical Society National Astronomy Meeting in Preston in April. Received wisdom regarding the local interstellar medium says that the whole Solar system is embedded in and close to the edge of a wispy diffuse cloud, known as the Local Cloud, or more esoterically, the 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 researchers used FUSE to probe the interstellar medium around a group of white dwarf stars. The data do not reveal the telltale ultraviolet fingerprint of oxygen, which should be present in the interstellar imprint. Instead, all the oxygen detected was found to be in the atmospheres of the stars with no oxygen present in the spaces in between. This, the team says, implies that, rather than being full of tenuous ionized gas, as supposed, the Local Cavity is instead empty. The team suspect that all gas was blown clear by the blast of an ancient supernova several million years ago. The researchers had initially hoped that the UV fingerprints from gas in the Local Cavity would show us its scars, the effects of nearby stellar events, such as supernova explosions, and radiation bursts from hot young stars. Unfortunately, the lack of hot gas presents us with little detail. One paradox remains, hot interstellar gas was also expected to emit detectable levels of X-rays, X-ray emissions are certainly observed, but obviously cannot originate in a material that is not present. One possible explanation is that the X-rays arise from the exchange of charged particles at the boundary between the Sun's magnetic field and interstellar space. Related links:
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