Чтение общенаучной литературы. Кытманова О.А. - 45 стр.

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46
electricity). In some cases nuclear power is used to give the satellites almost
endless working lives. For interplanetary travel lasers might possibly be used.
The laser's very intense beam of light can be modulated by signals to serve as a
carrier wave for speech.
RADIO ASTRONOMY
Until the middle of the 20th century,
astronomers could explore the universe only by
using optical telescopes to study the light from
planets, stars, glowing clouds of gas, and
galaxies However, many objects in the universe
are brightest at wave-lengths of electromagnetic
radiation outside the visible spectrum. In order
to "see" the stars and galaxies that emit radio
waves infra-red radiation, or X-rays, special
telescopes and detectors are needed. The
world's best infra-red telescopes have been set
up on high mountain-tops with pollution-free
atmospheres, such as Mauna Kea, a dormant
volcano on Hawaii. X-ray detectors have to be sent above the Earth's atmosphere
into space. The longest-established kind of "invisible" astronomy is radio
astronomy, and radio astronomers have found many objects whose existence had
hitherto never been suspected. For information on other branches of invisible
astronomy .
TELESCOPE
The view of the Universe through a radio telescope is very different from the
picture obtained by optical astronomers. Using optical instruments, we can observe
directly the light coming from stars, galaxies, and other objects. Radio
astronomers, however, detect the radio waves coming through space and use
complex equipment, such as computers, to interpret them. Radio waves can be
detected coming from our Sun, the strength of which varies with the sunspot cycle
(see SUN). The planet Jupiter is also a powerful radio source. This planet is
surrounded by an extensive and strong magnetic field. Electrically charged
particles passing through this field emit radio waves. Beyond the Solar System,
radio telescopes pick up a glow of emission from the Milky Way as well as from
several of the large clouds of gas, called nebulae. Within our Galaxy there are
rapidly-flashing radio sources called pulsars, while beyond the Milky Way lie
remote but extremely powerful radio galaxies and quasars. From the far depths of
space there is a background of radio emission left over from the birth of the
Universe itself—the echo of the "Big Bang" .
This article explains a little of the history of radio astronomy, the equipment used
by radio astronomers, and some of the great discoveries to which their work has
led.

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