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The Infrared Astronomical Satellite (IRAS)

March 25, 2009 Lowell Bradford Blog, News & Articles 0 Comments


The Infrared Astronomical Satellite (IRAS) was launched to map the sky with a special infrared telescope. A joint scientific project that is sponsored by the Netherlands, UK and USA, IRAS was launched in January 1983, and it completed its mission by the end of that year.


IRAS mapped 96% of the sky at 12, 25, 60, and 100 micrometer wavelengths four times over. Since IRAS was designed to map fixed sources, it scanned the same part of the sky a number of times. The resolutions that were used ranged from 30 arcseconds at wavelength of 12 micrometers to 2 arcminutes at wavelength of 100 micrometers.


IRAS was an infrared satellite, and it lasted for about 10 months. Infrared telescopes require an advanced cooling system because all objects emit infrared radiation at normal temperature. As such, certain parts of an infrared telescope (IR) must be cooled to prevent distortions during observation. Hence, to make the IRAS function, the telescope had to be cooled down to a temperature of 2 Kelvin (about ?271 °C). In IRAS, 475 liters of super fluid helium was used as the coolant. The evaporation of the helium helped retain the extremely low temperature. However, the on-board supply depleted within a year, causing the temperature to rise. With the rise in temperature, the infrared telescope’s observations came to a halt.


During its ten-month long observations, the IRAS discovered more than 350,000 sources, many of which haven’t been identified properly. IRAS observed 20,000 galaxies, 90,000 space objects, and 130,000 stars. About 75,000 of the observed sources are speculated to be starburst galaxies, while some others have been identified as normal stars that have stardust surrounding them. One such example is the dust disk around the star Vega, which is believed to be the nascent stage of a planetary system. The IRAS was also the first satellite to send images of the core of the Milky Way galaxy. It holds the distinction of being the first satellite to discover a comet as well. In fact, it discovered six comets altogether, which included 126P/IRAS, 161P/Hartley-IRAS, and IRAS-Araki-Alcock. The comet IRAS-Araki-Alcock was named after the astronomers who discovered it.


The most significant of IRAS’ discoveries was a new types of galaxies, called starburst galaxies. Compared to normal galaxies, formation of new stars is more rapid in starburst galaxies. Furthermore, a team at Leicester University, which was comprised of Jack Meadows, John Davies, and Simon Green, discovered three asteroids, which included 3200 Phaethon.


Following IRAS, there have been quite a few infrared telescopes which have continued to scan the universe. In the process, numerous stellar objects have been discovered, and invaluable data has been collected. Some of those telescopes in the last couple of decades were the Infrared Space Observatory which was established in 1995, the Spitzer Space Telescope which was launched in 2003, the AKARI Space Telescope which started in 2006, and the European Space Agency’s Herschel Space Observatory which was launched in April, 2009. All of their sensitive and unbiased surveys have contributed to a better understanding of the universe.

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