Pisces, the Fish
swim in the ocean of the sky where also can be found the sea monster Cetus. Nearby to the west along the ecliptic, Aquarius, god of the waters, may be seen as he pours out water to bring the gentle rains without which the Earth would be fruitless. (However, it was he who also caused the flooding of the Nile.) Above the swimming fish and to the west, look for the flying horse, Pegasus. The Great Square of Pegasus is one of the most prominent asterisms of autumn skies.
In the lore of the sky, these fish started out as gods. To the Greeks, they were Aphrodite and her son Eros. The Romans knew them as Venus and Cupid. A myth describes the mother and son strolling along a river bank. They encountered a terrible giant—Typhon. Startled and frightened, Venus and Cupid jumped into the river and assumed the form of fish. The other gods then elevated the fish to the sky as one of the groups of the zodiac. The stars were known as “Venus and Cupid,” in Roman times.
M74 is a
spiral galaxy seen “face-on.” It is typical of a grand-design
Sc galaxy. According to a classification scheme first worked out
by Edwin Hubble, the notations Sa to Sd refer to a simple spiral
form with a to d indicating increasing pitch angle. This galaxy
is at a distance of 30 to 40 million light years and is receding
at a rate of 800 km/sec. Along the spiral arms are clusters of
blue young stars. The spiral reaches out to cover a region of
more than 10 minutes of arc in diameter, corresponding to roughly
95,000 light years, about the same size as our Milky Way galaxy.
Discovered in 1780 by Messier’s associate P. Méchain,
this faint object in Pisces was not determined to have its spiral
characteristics until 1848. In smaller telescopes it appears as
a fuzzy disk with a brighter center. The constellation Pisces is a faint, but graceful and pretty pair of delicate streams of stars which come together to form a V. The point of the V is sometimes called the Heavenly Knot. Starlore says it’s the knot that ties two fish together by their tails. The two strings of stars diverging from the Knot culminate in the diamond-shaped figure called the Northern Fish, and the Western Fish, an attractive oval of fourth- and fifth-magnitude stars called the Circlet. The Circlet can be easily found below the Great Square of Pegasus.
The Vernal Equinox now lies in Pisces (originally this point where the Sun crosses the plane of the ecliptic was in the constellation of Aries). This is the point from which all right ascension coordinates are measured.
One of the brightest stars in Pisces is Al Rischa at the point where the two fish are tied. In fact, the name comes from the Arabic word for “cord.” Al Rischa, a-Piscium, is really a double star—two stars af magnitudes 4.2 and 5.1 that orbit each other once every 720 years or so. It’s interesting to note that the two stars whose name means “cord” really are tied together—by the long cord of gravity. With a separation of just 2 seconds of arc, this pair is a challenge for small telescopes, but the rewards justify the effort, for the stars are green and blue, with remarkable contrast.
Within the constellation lies one of our closest celestial neighbors. The faint star known as Wolf 28 is also called Van Maanen’s star, named for an astronomer who discovered the star in 1917, Adrian Van Maanen. He noticed that the star appeared to move quickly across the sky relative to other stars, indicating that it was nearby. Van Maanen’s Star is only 14 light-years from the Earth. Only a few stars are closer. It’s a white dwarf—a star that’s used up its nuclear fuel. Our own Sun will become a white dwarf—in another five or six billion years.
First seen in the late 1960s, a bizarre class of objects called gamma ray bursters can outshine the entire gamma-ray sky. For them to appear so bright, they must result from cataclysmic events—although there’s no consensus about their nature. The puzzle became even more complicated in February, 1997, when the orbiting Compton Gamma Ray Observatory and another spacecraft detected a burst in the constellation Pisces that lasted for an hour and a half—50 times longer than any other burst ever detected. Its energy level was 12 times stronger than any other burster. The burst might have come from matter spiraling into a black hole billions of light-years away or possibly from a collision between two neutron stars. But no one knows for sure.
Beginning in August bc7 there occurred in Pisces a rare triple conjunction of the planets Jupiter and Saturn. Three times in a single year these bright celestial objects appeared close to each other. Could this event have been the Star of Bethlehem?