According to legend, St. Patrick banished all snakes from Ireland, which is why we celebrate his life today. So, with the focus today being on St. Patrick and, to a lesser extent, snakes, why not take a moment to try and view the cosmic snake, Hydra, tonight?
When it comes to constellations, Hydra is a big as they come. While most people, when they hear the word ‘constellation,’ think of a pattern of stars, there is actually more than meets the eye. In truth, constellations are not just patterns of stars, but areas of sky that are dominated by a central stellar picture from which the constellation derives its name. Example: go out and look at Orion tonight and see the man-shaped pattern of stars. However, the constellation comprises the sky around the familiar shape, not just the shape itself. When it comes to fencing off the sky, that job falls to the International Astronomical Union (IAU).
Okay, back to Hydra.
While definitely not the most conspicuous constellation in the sky (actually far from it), at least in terms of sky area as defined by the IAU, Hydra is far and away the largest, comprising over 1,300 square degrees, or 3.16%, of the sky. In terms of length, the constellation spans over 80 degrees, stretching from just below Cancer nearly to Libra. When it comes to seeing Hydra, first look for its head just below Cancer, then go East, coming to +1.9 magnitude Alphard, the only star reasonably bright star in the entire constellation. From there, continue East, snaking your way (sorry) through the sky, going under Crater and Corvus and eventually coming to Gamma Hydra, just below Spica, and, from there, hopping one more star East to the end of the water snake’s tail.
Unfortunately, when it comes to seeing Hydra, the light-polluted skies of the Cleveland metro area do not bode well at all as the constellation is so dim. Now, if you live in the country or suburbs, the best time to see Hydra (at least in March) is about 2 in the morning, give or take an hour, as, being so large, one has to wait for meridian transit for the entire constellation to even be above the horizon. If you wait until 3am, Hydra’s head will be almost due West and about 20 degrees up while its tail will end just about due South at the same elevation.
As is the norm, be sure to keep an eye on the Cleveland weather forecast and, for hour-by-hour cloud predictions, the Cleveland Clear Sky Clock. So far, the upcoming week is looking rather cloudy. However, maybe a little luck of the Irish will be with you tonight in the form of a clear window in between all the clouds. Live somewhere else? Find a clock and see if it will be clear near you.
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