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Restless Nights in May

© Gregg Pasterick

The night sky is a pretty restless place, what with all that expansion of the universe going on. Of course, that takes place on such an incredibly huge scale, involving distances and lengths of time that are too big to hold in our heads without some leakage; the expansion is not obvious during the course of the night, or from one night to the next, or during a lifetime, even. We are too small and too brief in this incredibly huge restlessness to be able to actually see it. Oh sure, we can measure it, we can observe it by inference, but we can't actually see all that restless expansion. Much nearer home, home being Earth, we can see what a restless place the night sky can be, restless beyond the constant, casual wheeling of the constellations, that is.

The Moon and some of the planets change from night to night; occasional bits of interstellar dirt hit the atmosphere, incandesce, and streak among the stars; meteor showers turn the restless night sky into a pinball game; asteroids sneak about; manmade satellites follow precise paths... I'd say the night sky is a very restless place. This month is a good example of that. We have a meteor shower; we have an asteroid; we have the planets and the moon. It might all just sound like more of the same, but more of the same means restlessness.

Early in the month, we have the Eta Aquarid meteor shower, and three nights later the asteroid 1 Ceres is at opposition. The Moon and Jupiter dance cheek-to-cheek on the 19th (of course, during the course of any month, the Moon behaves flirtatiously with a host of suitors.) Saturn and Pollux do the same at month's end as they are in conjunction for the third and final time. Mars and Uranus dance the dance on the 15th. There is all sorts of restless behavior going on in the night skies of May. Let's look at a couple, shall we?

1 Ceres is at opposition on the 8th, at 16:00 U.T., which means it is 180 degrees across the sky from the sun, and thus best situated to be observed. It will be a bit above the second brightest star in Libra, Zubeneshamali. It will be faint - magnitude +7.0 at this time - so observers will need binoculars to see it, but it's a chance for a little homework. Armed with those binoculars and a good star map, observers should be able to pick out 1 Ceres from night to night because it will have moved from west to east. (Zubeneshamali is interesting, by the way. Thomas Webb, an English astronomer during the 19th Century, described its color as "deep green, like blue, is unknown to the naked eye." Eratosthenes, a Greek stargazer way back in the 2nd Century B.C., called Zubeneshamali "the brightest of all" the stars in the region, which included Antares. More than 300 years later, Ptolemy considered Antares and Zubeneshamali the same magnitude, which no longer is the case: Antares is about magnitude +1.0, while Zubeneshamali is fainter at about magnitude +3.0.)

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