Night owls and early birds can catch a glimpse of Comet Ikeya-Zhang as it passes by Earth in the next few weeks on its four-century journey around the Sun.
The comet passed closest to the Sun on March 18th, and is now headed out of the solar system past Earth, passing closest to us (just 37.5 million miles, or 60 million kilometers) on April 29. To see the comet, look low in the western sky during late evening twilight. The comet will get lower and lower on the horizon until April 4; after that it will be visible in the early morning sky in the east.
"The comet is bright enough to see with the naked eye, but having binoculars or even a small telescope will help pinpoint its location," said Dr. Don Yeomans, head of NASA's Near-Earth Objects Program Office at the Jet Propulsion Laboratory, Pasadena, Calif.
Among the comet-watchers will be Dr. Michael Hicks, a comet scientist from JPL. Hicks will use a telescope to study the dust from Ikeya-Zhang, dust that comes from the very edges of the solar system and has a sharply slanted orbit, compared to the planets. The information he hopes to gather includes the dust particles' size, temperature and composition.
"Comet dust is some of the most pristine material from the solar system's formation," said Hicks. "Studying comets adds another little bit to the puzzle of how the solar system came to be."
Comets, clumps of rock and ice, were made when the solar system formed 4.5 billion years ago from the same material that made the planets and Sun. When its orbit takes it far from the Sun, the low temperature of deep space keeps the comet frozen. As the comet comes close to the Sun, it heats up, emitting gases and the dust that reflects the Sun's rays and makes the comet visible from Earth.
Ikeya-Zhang, which was discovered in early February by a Japanese and a Chinese astronomer, was likely seen in 1661 on an earlier journey through the solar system.
JPL, a division of the California Institute of Technology, manages the Near-Earth Objects program for NASA's Office of Space Science, Washington, D.C. More information is available at http://neo.jpl.nasa.gov and http://www.jpl.nasa.gov.