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By pointing NASA’s Chandra X-ray observatory towards Comet LINEAR,
astronomers have worked out how icy comets generate X-rays. Normally only very
hot objects produce X-rays, but some were spotted coming from Comet Hyakutake
four years ago. The researchers found that the X-rays LINEAR is giving off come
from ionised oxygen and nitrogen in the solar wind, which capture electrons from
the cometary material. As the electrons drop to lower energy levels they emit
X-rays, says Carey Lisse of the Space Telescope Science Institute in Baltimore.
Cometary X-rays could be used to probe the solar wind anywhere in the Solar
System, Lisse says.