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A new comet that will pass close to Earth early next week has been discovered by scientists working on the international Infrared Astronomical Satellite project.
The comet first appeared in data sent to Earth on April 25, in IRAS' routine search for asteroids. When it was photographed later by ground-based telescopes, the object was identified as an extremely fast-moving comet.
This marks the first time comet has been discovered using an instrument that measures temperatures, rather than visible light. It is also the first time comet has been seen at far-infrared wavelengths, where very cold objects emit most of their radiation.
The new comet will make its closest approach to Earth on the evening of Tuesday, May 10. The accumulated brightness of the entire comet will be equal to that of the brightest stars in the sky, but because its light will be spread over an area 16 times greater than the area of the Moon, it will be difficult to see with the unaided eye unless the sky is quite dark.
Preliminary data on its orbit indicate the comet will pass about 5 million kilometers (3.1 million miles) from Earth -- 12 times the distance of the Moon. Only one other comet has been known to pass closer to Earth.
At the time of its discovery by IRAS, the comet was about 90 degrees from the Sun. It was too dim to be seen with the unaided eye, the IRAS scientists said, although it was extremely bright in the IRAS infrared telescope.
The new comet will pass quickly across the sky, scientists say, and will move the equivalent of four times the Moon's apparent diameter every hour.
The comet has been named IRAS-Araki-Alcock, for the observers who reported its discovery. Genichi Araki is Japanese amateur astronomer and G.E.D. Alcock is British amateur astronomer. They reported sighting the comet simultaneously with the IRAS science team.
The Infrared Astronomical Satellite is joint project of the U.S. National Aeronautics and Space Administration, the Netherlands Space Agency, and the British Science and Engineering Research Council. Jet Propulsion Laboratory is the U.S. management center. Data from IRAS are received at the ground station at Chilton, England.
Comets have been observed since ancient times. The best known of all comets was named for Edmund Halley, and has been observed every 75 to 76 years. Halley's Comet was recovered last October using the 200-inch telescope at the Palomar Observatory, and will make its next pass by the Sun in 1986. Astronomers are not certain where comets originate, but many believe they exist in cloud of matter left over from the formation of the solar system. The so-called Oort Cloud, they say, is at the far edge of the solar system.