Looking back: The Sky at Night

1 October 1983

On 1 October 1983, The Sky at Night took a look at the work being done by NASA’s Infrared Astronomical Satellite (IRAS). Since January of that year, the observatory had been surveying the entire night sky at infrared wavelengths. As the

Earth’s atmosphere soaks up most of these wavelengths, the space-based IRAS was the first time astronomers had

NASA’s IRAS revealed over a quarter of a million infrared sources been able to accomplish this task.

The mission ended in November 1983, when the spacecraft ran out of the helium it used to cool itself. By then it had surveyed the sky four times and revealed over a quarter of a million infrared sources. These ranged from asteroids and comets, to dusty discs around stars that would go on to form planets, all the way out to distant galaxies bursting with newly born stars.

With rules to mitigate space junk still decades away, NASA left the satellite in orbit. It was a decision it almost came to regret when, on 29 January 2020, IRAS nearly collided with a defunct military satellite: astronomers watched nervously as the two craft squeaked past each other, passing with as little as 13m between them. Fortunately, no new space debris was created by the meeting.

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