Eridanus, the River
is south of Orion and
Taurus in the evening skies of December and flows further south
well below our horizon. Its brightest star, Achernar, is ninth
on the list of bright stars, but it is a star we cannot see, unless
from Hawaii, Florida or south Texas. Only one other star in the
constellation ranks brighter than third magnitude. That is Cursa,
at magnitude 2.9, just three degrees to the northwest of Rigel
in Orion. From this point in the heavens the river wends a long
and twisted way to its terminus at Achernar. It is indeed the
longest pattern in the sky, and its boundaries enclose the largest
area of any of the constellations.
Phaethon lived with his mother Clymene, who told him that he was
of divine birth and that his father was Apollo, god of the Sun.
At school, however, Phaethon was taunted by his fellows, who demanded
proof of his claims. He went to his mother, who said that if he
needed to know more he must ask for his father's acknowledgement.
So he travelled to the east until he came to the palace of the
Sun, aloft on columns glittering with gold and precious gems.
Approaching his father, the youth was welcomed, and he asked,
Give me some proof by which I may be known as yours.
Apollo replied, My son, I confirm what your mother has told
you. As further proof, ask what you will and the gift shall be
yours. Phaethon immediately asked to be allowed to drive
the chariot of the Sun one day. But Apollo demurred, saying, I
have spoken rashly, for your request is not safe for you, nor
for any of the gods but myselfnot even for Jupiter. Yet
the oath is sworn and must be kept, if you must have it so.
Phaethon was adamant, as daring but unwise youngsters are, and
he was led to the stables where the diamond-studded golden chariot
was ready for the dawn. Apollo admonished the youth to hold tight
the reins and to steer a straight and middle course, avoiding
both the southern and the northern zones. Led by the morning star,
the stars withdrew.
The snorting steeds began their journey, but sensed that they
were being driven by an inexperienced charioteer. They veered
to the right, and the Great and Little Bears felt a scorching
pain and would have plunged into the sea had they been able. The
boy looked to his left and saw the reaching claws of the Scorpion:
his courage failed him and he dropped the reins. The horses dashed
headlong, now high, now low almost to the mountaintops, the trees
and fields withering and ablaze. The deserts remain dry forever
Earth called on Jupiter, ruler of the gods, to deliver all from
the awful scene. And Jupiter, recognizing the peril, launched
a lightning bolt against the charioteer, striking him from his
seat and sending him into the Eridanus, like a shooting star which
marks the heavens with its brightness as it falls. Afterward,
to console Apollo for the loss of his son, Jupiter placed the
river in the sky.
Other associations for this river in the sky have been put forth,
including a representation of the Nile, mentioned by Eratosthenes,
the Greek astronomer and mathematician of the third century bc.
The Tigris and Euphrates are also linked to this constellation,
and even the River Jordan, the Po in Italy, the Rhine in Germany,
the Rhône in France, and the Ebro in Spain. Might it not
as well represent the Rio Grande, flowing south as far as any
major river in the continental United States?
Except for the Alpha Centauri and Sirius systems Epsilon Eridani
is the star closest to us at about eleven light years distance.
As early as 1973 it was found that this star has a companion with
a mass less than 0.05 that of the Sun. Separated from Epsilon
Eridani by about the same distance as Saturn is from the Sun,
this object may be a large planet or one of the smallest stars
In 1998 astronomers reported a ring of dust around Epsilon Eridani
that is strikingly similar to the inner comet zone
in the solar system and shows an intriguing bright
region that may be particles trapped around a young planet. The
research team included astronomers from the Joint Astronomy Center
in Hawaii, UCLA and the Royal Observatory in Edinburgh, Scotland.
image shows the emission from dust particles orbiting around Epsilon
Eridani. The dust lies mainly in a ring around the star, with
a radius of 60 Astronomical Units. The star itself was not seen,
because its small, hot surface radiates very little at submillimeter
On the outskirts of the Solar System, there are vast numbers of
comets beyond the orbit of Pluto (40 AU) making up the Kuiper
Epsilon Eridani is much younger than the Sun, only about 0.5-1
billion years old while the Sun is 4.5 billion years old. It is
likely that tiny dust particles around Epsilon Eridani will gradually
accumulate into comets like those in the Solar System's Kuiper
The one prominent bright peak in the ring around Epsilon Eridani,
seen to the lower left of the star, could be dust particles trapped
in an orbit close to a planet, or (less likely) the remnants of
a major comet collision. No one yet knows if Epsilon Eridani has
planets, but the new image gives a clue that there may be.