Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer. Perhaps 20 kilometers across but with more mass than the Sun, this ultracompact object is the collapsed core of a massive star. The core collapsed when the star, located a reassuring 5,000 light-years away in the constellation Gemini , exploded long ago. Judging from the characteristic bow wave shape of the x-ray nebula the researchers have estimated the speed of the neutron star as it plows away from the explosion site. Comparing the speed to the measured distance traveled from the center of IC443, the team , three high school students and a teacher from the North Carolina School for Science and Mathematics, calculated that the light from the supernova explosion arrived at Earth about 30,000 years ago.
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