पृष्ठम्:ब्राह्मस्फुटसिद्धान्त भाग १.pdf/४७

ASTRONOMY IN ANCIENT NATIONS
In the case of Sirius, the
they were last seen to set after sunset.
brightest fixed star, these would happen when the Sun was about
ten degrees below the horizon. For the less bright stars the
angle would be a larger one.
It must have been almost simultaneously observed that the
Moon in going like the Sun round the heavens always in the
same direction from west to east (i. e., opposite to the diurnal
motion which she shares with the other bodies), kept in general
to the same track in the sky. After a time, however, it must
have been noted by careful observers that this path was not con-
stant, but deviated from the centre line of the Zodiac, getting
away from that line up to a maximum deviation on either side
but slowly returning to it. In the course of a number of years, it
must have become evident that the Moon's path among the stars
does not lie always in the same line on the celestial sphere, but
in a zone or band about twenty moon breadths (10") wide, occu-
pying the middle of the Zodiacal zone itself.
Among the bright stars Mercury. Venus, Mars. Jupiter
and Saturn (the first two of which are never seen very far from
the Sun in the sky) soon must have been noted to be moving in
the Zodiac with varying periods. The English name planet is de-
rived from Greek planetes, meaning a wanderer, since the planets
change their positions among the Zodiacal stars.
There is a word Sty which in the Rgveda always occurs in
the instrumental plural, Strbhiḥ. The English word star is de-
rived from this word. Parāśara and Grtsamada, I have shown
elsewhere, were the first amongst the great observers, inspired by
the Rgvedic hymns, and Vamadeva identified Brhaspati or the
Jupiter planet and Vena Bhargava discovered the planet Venus
which still bears the name of its discoverer.
Constellations
Long before the Zodiacal belt was divided into "signs" (700
B. C.), a number of asterisms, or the configuration of stars in the
sky had been arranged, the brighter stars of these configurations,
thus identifled, proved very useful in indicating the seasons of the
year by the times of their rising or setting, and also in locating
the positions on the celestial vault of such moving objects as
planets, comets and shooting stars and in helping the traveller
by land or sea to determine direction.