Sky Watch: Watery constellations

Scientists have estimated that our planet may be home to at least 10 trillion trillion animals fitting into more than 7.8 million species. Spend any time under a dark night sky with a star map and you'll be surprised at how many of these have made their way into the heavens. Of the 88 official constellations, at least half represent some sort of animal -- real or mythological.

Not all of these celestial creatures come from the land; many are animals whose homes are in the watery depths of the rivers, lakes and seas. And they are not just animals, either. Other watery subjects also appear among the stars -- particularly at this time of year.

One of the largest and most prominent of these is the constellation of Aquarius. Look for this relatively faint star grouping high in the southeastern sky during late nights this week.

Aquarius forms a small Y-shaped pattern that is known today as the water-bearer or water jar; classically, sky watchers have often depicted it as a standing man, pouring liquid from a jar. Try to see that form in the sky, however, and your hair will turn as white as mine.

The figure of Aquarius first appeared on ancient Babylonian stones, but it seems to have represented water in many ancient cultures including Persia, Israel, Syria, Turkey and Arabia. Ancient Egyptians, for example, knew it as Monius who filled his giant urn by descending into the Nile River and causing it to flood each June when the midnight sky showed Aquarius at its zenith.

Of course, one would expect that where there's water, there's fish. And, sure enough, that's true in the heavens as well. A quick glance to the east of Aquarius reveals the constellation of Pisces, the fishes, supposedly tied together with rope. More precisely, it should be called the northern fishes, because there's also a constellation of the southern fishes (Piscis Austrinus) just south of Aquarius. And if you thought it was tough to outline the namesake of the northern fishes, get ready for some fun here! Fortunately, a bright star named Fomalhaut marks the constellation and makes it much easier to find.

Just below Pisces swims one of the largest creatures in the sea: Cetus, the sea monster or whale. Cetus is said to be the beast that Poseidon sent to plague the king Cepheus when the queen Cassiopeia claimed to rival the Nereids in beauty -- placed in the heavens to commemorate his heroic deed. With some imagination, one might almost be able to make out the whale's huge body, with its tail and fluke stretching toward the east.

Pay close attention to the nighttime sky throughout the year and you'll discover many more of these watery constellations: Delphinus, the dolphin, Dorado, the swordfish, Carina, the ship's keel, Hydra and Hydrus, the water snakes, Vela, the sails, and many more. Stargazers in the Earth's Northern Hemisphere can see many of these in their entirety -- others only partially -- but some can be seen entirely from south of the equator.

All have rich histories that date back centuries, and often, millennia, so get out there this week and begin your search!