Чтение общенаучной литературы. Кытманова О.А. - 47 стр.

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the 76.2-meter (250-foot) paraboloid dish at Jodrell Bank, in Cheshire. England,
completed in 1957, and the instruments at Parkes, New South Wales (Australia),
and Goldstone, California (United States). The huge size of these single-dish radio
telescopes makes them very expensive to construct and maintain, and they take
years to build. For these reasons radio astronomers developed a different type of
telescope consisting of several smaller dishes which are linked electronically.
These act together just like one enormous instrument. By joining two or more
dishes together, thus forming what is called an interferometer, some of the qualities
of a very large telescope can be obtained, in particular the ability to "'see" fine
detail in a radio source. Each dish in the array, or linked group, is pointed at the
same radio source. The Earth spinning on its axis causes the array to rotate beneath
the sky. Computer analysis of the signals obtained over many days of observing
the same object can then mimic the effect of a huge optical telescope.
A telescope of this type, 4.6 kilometers (2.8 miles) long, at Cambridge in England
stands on the site of a former railroad track. There are others in The Netherlands
and Australia. At Socorro in New Mexico is the world's largest interferometer, the
Very Large Array (VIA), completed in 1979. It has 27 antennas, each of which is
movable along the three arms of a Y-shaped array; each arm is 20 kilometers (12.4
miles) long. The VLA can map small radio sources with the same precision as the
best optical telescopes.
Radio telescopes in different countries a great distance apart can be linked
electronically. This arrangement, called very-long-baseline interferometry (VLBI),
allows fine structure to be mapped in very distant radio sources in greater detail
than any optical telescope has achieved.
Radio Sources
The unfolding picture of the radio universe, as briefly described in the first
section of this article, has provided some surprise discoveries. Here in more detail
are just some of them.
Pulsars are tiny, heavily condensed neutron stars that rotate at very high speeds.
The first pulsars were detected by radio astronomers in Cambridge, England, in
1968. Their radio emission consisted of a series of extremely regular pulses
separated by a second or less. For a time scientists thought the pulses might
Ionized hydrogen in the Horsehead Nebula in Orion is set aglow by nearby hot
stars. It emits radio waves as well as visible and ultraviolet light be interference,
but they soon realized that they were really linked with neutron stars many light-
years beyond the Solar System.
Hundreds of these pulsars are now known. Some send very rapid signals: 30
times a second for the one located in the Crab Nebula, and 642 times a second for
one found in 1982 in the constellation Vulpecula. An explanation of pulsars and
why they generate regular bursts of radiation can be found under STAR.
Supernova Remnants. The gas thrown into space by a supernova explosion (a
huge explosion in which some massive stars meet their ends) may itself be a
detectable radio source. One of the strongest of these supernova remnant sources is
the Crab Nebula in the constellation Taurus. This glowing cloud is the remains of a
star seen to explode in 1054. Some supernova remnants are almost invisible

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