Чтение общенаучной литературы. Кытманова О.А. - 48 стр.

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49
optically but show up strongly in radio maps of the sky.
Radio Galaxies. The year 1951 was a crucial one for the new science of radio
astronomy, One of the strongest sources was found to be a galaxy 500 million light
years away, then considered a fantastic distance. Astronomers realized that this
object, called Cygnus A, had to be making the radio waves in some extremely
powerful way in order for them to be detectable at such a distance. In fact the
radiation from Cygnus A is about a million times more powerful than the waves
from our own Galaxy. Hundreds of similar galaxies are now known to be radio
galaxies.
The radio waves are produced by electrons accelerated to near the speed of light
through magnetic fields that surround the galaxies. This form of radio emission is
known as synchrotron radiation. Some sources are double, some have jets, and yet
others have long tails as if leaving a wake caused by motion through the Universe.
The investigation of these energetic and remote galaxies led to an even more
intriguing discovery—quasars. Quasars, Discovered in 1963, quasars are objects
with starlike images and very large redshifts (see UNIVERSE.) If the redshifts can
be interpreted as equivalent to vast distances, then quasars are extremely remote
objects, perhaps about the size of the Solar System, putting out as much energy
(both light and radio waves) as 1,000 normal galaxies. It is possible that radio
galaxies and quasars have at their centers enormously massive black holes .
The Nature of the Universe
Radio astronomy has made two major contributions to our understanding of the
Universe. The first is connected with radio galaxies and quasars. The work of radio
astronomers suggests that there were once a lot more radio galaxies than there are
now, because there seem to be many more of them at great distances (and therefore
earlier times) than there are nearer to us. This suggests that the ''steady state"
theory of the Universe once held by some astronomers is wrong, for according to
it, the Universe never changes its basic appearance.
The second discovery was that of the "microwave background radiation" in 1965.
Many theorists consider this the most important finding in astronomy in the last
half century. US radio astronomers found that surprisingly strong radiation was
reaching the Earth, which did not seem to have any particular source. It was
equally strong in all parts of the sky. Most astronomers accept that it is left over
from a much earlier phase of the Universe. It may even be the remains of the
fireball that started the expansion of the Universe.

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