Astronomers have made rare images of the heart of a popular comet and revealed jets of gas spiraling thousands of miles into space. Comet McNaught has been called the Great Comet of 2007 for the show it put on first in the Northern Hemisphere and then south of the equator. The ball of ice and dirt hung frustratingly close to the Sun, however, so many skywatchers never got a good look. The New Technology Telescope (NTT) at the European Southern Observatory in Chile was used to make detailed observations that were released yesterday. Scientists found sodium in the comet's emissions,...