Page 255 - Inventions - A Visual Encyclopedia (DK - Smithsonian)

SPLITTING LIGHT
US_252-253_Studying_the_stars_Main.indd
The spectroscope was invented in 1814 by the German physicist
Joseph von Fraunhofer. It spreads light rays from stars onto different
paths depending on their color or energy. Fraunhofer discovered
dark, narrow lines in the sun’s spectrum, which later scientists linked
to light being absorbed by particular chemicals. Astronomers today
use spectroscopy to study what celestial objects are made of.
Dark absorption
lines are created
Light from the by star’s chemicals
sun enters here absorbing light
Overall pattern of
Laser beams projected from spectrum from
the VLT produce artificial infrared up to
stars in the upper atmosphere, ultraviolet reveals
which the telescope uses to temperature of star
monitor its performance
and create sharper images.
Solar spectroscope, Spectrograph
1881 of a star
SPACE TELESCOPES
Visible light is just one part of the electromagnetic
radiation emitted by cosmic objects. Things too cool
to shine visibly still emit infrared radiation (heat), while
very hot objects and violent events release high-energy
ultraviolet, X-rays, and gamma rays. Earth’s atmosphere
blocks most of this radiation, so astronomers use
space-based telescopes to map the sky.
Chandra X-ray Observatory Nested mirrors
deflect and focus
X-rays from distant
exploding stars.
SMART TELESCOPES
All modern large telescopes are reflectors. Some have
huge one-piece mirrors made of thin, lightweight
materials, but most use interlocking honeycomb grids
of smaller mirrors to reduce their weight. Computer-
controlled motors behind the mirrors can adjust their
overall shape to correct distortions and ensure perfect
focus for whichever direction the telescope is pointing.
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