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This satellite can observe wavelengths that cannot be seen
from earth. This instrument can image dust clouds and planets around nearby
stars. The new Hubble infrared spectrometer will replace many of the tasks
that this satellite has performed.
Infrared radiation has lower energy than visible light and is produced by
relatively cool objects, in the temperature range between 3 degrees and
1500 degrees Kelvin. (Ambient temperature on earth is about 300K.) Quite
often, visible light from cosmic sources is obscured by interstellar dust,
but infrared light passes through. Thus, invisible stars and galaxies can
be "seen" in the infrared region. The redshift due to the expansion
of the Universe shifts energy to longer wavelengths. The amount of the shift
is directly proportional to how far away an object is. As a result, the
high z objects we observe today are as they appeared when they (and the
Universe) was younger (because the speed of light is finite). Since the
Universe is expanding most of the visible and UV radiation from astronomical
objects has shifted into the IR.
©1997 The
Exploratorium
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