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This image from NASA's Wide-field Infrared Survey Explorer (WISE) features comet 65P/Gunn. Comets are balls of dust and ice left over from the formation of the solar system. As a comet approaches the sun, it is heated and releases gas and dust from its surface, which are blown back by the solar wind into a long, spectacular tail. Comet 65P/Gunn's tail is seen here in red trailing off to the right of the comet's nucleus. Comet 65P/Gunn was discovered by James Gunn, a professor at Princeton University, N.J., in 1970. WISE observed the comet on April 24, 2010, in the constellation Capricornus (just one month after the comet's closest approach to the sun). This is a single-frame observation, covering an area of 1.5 by 1.5 full moons (0.76 by 0.76 degrees). Comet 65P/Gunn is what is called a short-period comet. It orbits the sun inside the main asteroid belt between the orbits of the planets Mars and Jupiter. The orbit of 65P/Gunn is relatively round compared to many comets, and it takes 6.79 years to complete one trip around the sun. At the time that this image was taken, the comet was at a distance from Earth of 392 million kilometers (243 million miles). For reference, the average distance between the Sun and Earth is 150 million kilometers (93 million miles). The comet's speed relative the sun, when this picture was snapped, was about a whopping 7,700 kilometers per hour (4,800 miles per hour). Just ahead of the comet is an interesting fuzzy red feature that makes it look something like a swordfish, or narwhal. This "sword," or dust trail, is made of dust particles that have previously been shed by 65P/Gunn as it orbits the sun. The dust is warmed by sunlight and glows in infrared light. Trails appear both ahead and behind the comet?s nucleus and have a narrow, contrail-like appearance. They represent the first stages in the evolution of meteoroid streams. Over time, the material in the debris trail can drift away from the comet?s orbit and become clouds of debris t (KEYSTONE/SCIENCE SOURCE/Science Source)