There is a marvelous story from Chinese
legend about the Goddess of Weaving, Chih Nü, and her beloved,
Ch'ien Niu, a handsome young shepherd in the Emperor’s household.
This myth tells of the separation of the two by royal decree,
with the final provision that only on the seventh day of the seventh
month might the two lovers meet. It seems that on that day all
the magpies of the world gather to form a bridge across the river
of heaven with their wings; and on that bridge Chih Nü may
cross. Chih Nü is Vega; Ch'ien Niu is Altair, the Eagle of
our constellation Aquila, lying across the river of heaven, the
Milky Way. This story was repeated in the September, 1995, issue
of the Refractor.
There is another story from the
Far East that confirms this tale. The account begins two thousand
years ago, in the Han Dynasty, when it was supposed that the Yellow
River had its source in the Milky Way. The emperor Wu Ti determined
to know the truth, and he selected the courtier Chang K'ien, an
able and experienced adventurer, to sail upstream to the headwaters
of the Yellow River.
Chang K'ien set out, and he sailed for several moons, past farms
and villages, through fine weather and foul, through narrow gorges
and through placid waters, following the river as it twisted its
way, always to the west. At length, he came to a place like no
other; and when twilight came the night remained bright, more
brilliant than under a full moon. The stars did not twinkle and
they seemed exceedingly near. He recognized none of the constellations
he knew so well.
He saw no people as he sailed along; but he did find a paradise
of fragrant trees, with rainbow-winged birds happily singing among
the branches. He caught a glimpse of the rabbit of the moon, and
as he traveled onward, he passed the great beasts who ruled the
four quarters of the sky: the blue dragon, the scarlet bird, the
black tortoise and the white tiger.
Finally, Chang K'ien noticed a beautiful young maiden, along the
bank of the river, weaving a magnificent tapestry of iridescent
colors on her loom. He stopped and asked her where he was, for
he was surely beyond the Han empire of Wu Ti.
The maiden smiled and shook her head. She replied, “Take
this shuttle from my loom and return to your own city. Show it
to Kün P'ing, the astronomer, and tell him of your travels.
He will tell you where you have come to.”
Chang K'ien made the arduous journey down the river, and, on his
return to the court of Wu Ti, he requested that he be allowed
to see Kün P'ing. He gave the shuttle to the most learned
man, who studied it with curiosity and amazement.
“There is no doubt,” the astronomer said. “On the
seventh day of the seventh month I was observing the annual meeting
of the Weaving Goddess Chih Nü and the Herdsman Ch'ien Niu,
when I also saw a guest star come between them. I wondered about
it, but now it is certain that the stranger star was you, sailing
on the celestial river.”
The bright star Altair forms one vertex of the familiar Summer
Triangle, together with Deneb in Cygnus and Vega in Lyra. Long
ago, the constellation of Lyra was known as a vulture. It is possible
that in ancient times, these were identified as the three Stymphalian
birds, man-eating beasts with claws of iron, that Hercules faced
in the sixth of his twelve labors.
Aquila, Cygnus and Lyra (as the vulture) are among several birds
represented in the mythology of the heavens. The early seventeenth-century
German astronomer Johann Bayer, the first to publish an organized
chart of the constellations, the Uranometria, added the
southern constellations Grus, the crane, Tucana, the toucan, Avis
Indicia (now Apus, the bird of paradise), Pavo, the peacock, and
the miraculous Phoenix. Columba, the dove, was not established
until 1679, by Augustin Royer.
Altair is the brightest star in the constellation, and it is easily
recognized, accompanied on either side in a straight line by Alshain
and Tarazed (Beta and Gamma Aquilae). Altair is a remarkable star.
It is one of the nearest of the bright stars, and it has a large
proper motion. It is also known for its exceptional rotational
rate. As measured by Doppler shifts, it turns more than three
times in one of our days, compared to one turn in 25 days for
our Sun.
For some time, in 1918, Altair was only the second brightest star
in Aquila, for on the night of June 8 Nova Aquilae 1918 appeared
with a brilliance second only to Sirius in the entire sky. By
the following spring, however, the nova had faded below naked-eye
visibility. Other novas have appeared more than eight times in
Aquila during the last hundred years. Perhaps there was indeed
a guest star there during the Han Dynasty.
Eta Aquilae is a supergiant Cepheid variable which brightens from
magnitude 4.4 to 3.5 and dims again with a period of just over
a week’s time. For binocular viewing, there is an open cluster
of stars, NGC6709, seen against a rich background of Milky Way
stars. There are several fine multiple stars and planetary nebulas
for appreciation in a small scope.
