Nov 22 1983
From The Space Library
The Infrared Astronomical Satellite (IRAS), launched on January 25, 1983, as a joint project of the United States, the Netherlands, and the United Kingdom, depleted its supply of helium at 1:30 a.m. GMT. The superfluid helium refrigerant cooled the telescope, which would cease operations in about a week, mission officials said. Throughout the mission, the telescope's focal plane was cooled to a temperature of about 2.5 ° above absolute zero (-455 °F), making the instrument the coldest manmade object ever flown in Earth orbit.
The telescope surveyed more than 95% of the sky, pinpointing the locations and intensities of more than 200,000 infrared objects. During its 300 days of observations, IRAS carried out the first complete survey of the infrared sky and made many discoveries, including the detection of a ring of solid material around the star Vega and seven comets and bands of dust around the Sun between the orbits of Mars and Jupiter. More than 200 billion bits of data came from IRAS, and results announced to date represented only a hurried look at a very small proportion of this data. It was evident, however, that IRAS would have a major impact on many areas of astronomy and that astronomers would be making new discoveries from its data for years to come.
On November 9, NASA announced two IRAS findings: a new object in the solar system-possibly an asteroid or a dead comet-that passed closer to the Sun than any planet or known asteroid and three giant rings of dust that circled part of the solar system. The unknown object, temporarily designated minor planet 1983TB, appeared to be less than 2 kilometers (1.2 miles) in diameter and about 30 million kilometers (19 million miles) from Earth. 1983TB passed within 15 million kilometers (9 million miles) of the Sun, closer than any planet or known asteroid and 10 times closer than Earth. And its orbit almost exactly matched that of the Geminid stream of meteoroids, which were visible as a shower of meteors (shooting stars) in December 1982. Astronomers were planning additional observations with photometers and spectrometers in an effort to clear up the mystery of the identify of 1983TB. The three dust rings were 100 million miles wide and were circling the asteroid belt between Mars and Jupiter 200 to 300 million miles from the Sun. The dust bands appeared to defy the laws of physics by encircling the asteroid belt in three extremely stable and symmetrical rings. Particles making up the dust bands "this small can only survive in stable orbits for a few ten-thousands of years before they are pulled apart by the sun," said Dr. Frank Low of the University of Arizona. "There must be something that replenishes the rings because three stable bands that large cannot exist any other way." In addition, NASA announced that same day that astronomers studying IRAS data at the University of Groningen, the Netherlands, had discovered three giant dust shells that were asymmetrically placed around the star Betelgeuse. It was already known that the red supergiant star lost material, but IRAS data showed evidence of the presence of dust shells that extended more than four light years from the star. At that distance, the material must have left the star 100,000 years earlier. The IRAS observations thus allowed astronomers to study the earliest stages in the episode of mass loss. (NASA Release 83-162, 83-171, 83-172, 83-181; W Post, Nov 10183, A-1)
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