The discovery of a new comet is always of considerable interest to the
scientific world. Professor Baade, of Hamburg, has just announced that
he has discovered a new comet in the constellation Cygnus. This comet
is too faint to be seen without a telescope, but is rapidly increasing
in brightness, and has increased since its discovery from magnitude 115
to magnitude 9. It must, therefore, be rapidly approaching our solar
system at great speed.
This question of the velocity of comets is very remarkable, some of
them reaching the inconceivable speed of a million miles an hour.
Some of them are seen but once in several hundred years, but modern
astronomical science is so perfect that it is possible to predict the
precise day and hour of a comet’s return, several hundred years hence.
The comet is usually composed of three parts--the nucleus, the coma,
and the tail. The nucleus is the bright centre which resembles a star
in appearance. The coma is the luminous hood-like envelope by which the
nucleus is covered. The tail of the comet is composed of luminous gas,
which streams out from the coma sometimes for many millions of miles.
One interesting fact about comets has only been explained of late
years, due to the genius of Professor Arrhenius, of Sweden. It had long
been noticed that the tail of a comet invariably turns away from the
sun--that is to say, as the comet travels across the heavens, the tail
turns so that it always streams away from the direction of our central
luminary.
Why is this? The explanation is that the light-rays coming from the sun
exert a definite physical pressure, and this pressure is sufficient to
push the gaseous particles composing the comet’s tail away from it so
that the tail is invariably seen to flow away from the sun.
Comets invariably travel in an elliptical course. They come from the
vast depths of space, approach our sun, traveling with greater and
greater speed as they do so, then “turn tail” (in two senses) and
retreat again into the vast depths whence they have emerged. The size
of the curve taken by the comet enables the astronomers to calculate
the exact date of its return, once they have ascertained the speed with
which the body is traveling.
Comets bring home to us, perhaps, more than any other astronomical
phenomena, the relative brevity of human life. Some comets return
but once in several thousand years. One such was noted a few years
ago. When last seen by inhabitants on this earth it must have been
before the greatness of Greece and Rome, before the building of the
pyramids and the civilization of ancient Egypt! When next it returns,
civilizations now existing may have ceased to be! Continents may
have been submerged. The whole fate and future of our race may have
undergone a profound change. All this in but a single sweep of one body
through the vast stretches of stellar space!