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Sky Watch
by J. Alex Knoll
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Blazing Cosmic Flotsam
It’s not a pyrotechnic bonanza, but July’s Southern Delta Aquarids put on a show
The waxing crescent moon begins its climb into our evening skies, appearing as a thin crescent low in the west at dusk Thursday. Lined up diagonally beneath it are Mars and Regulus, the heart of Leo the lion. Spying either is a challenge so close after sunset, around 8:20, and so near the horizon. Although Regulus is lower and of course much more distant, Mars is near its farthest point from both the sun and from earth, so that it shines no brighter than your average star.
Friday marks the peak of summer’s best meteor shower, the Southern Delta Aquarid, with stray shooting stars appear sporadically for more than a week afterward. The young crescent moon sets early, and this display is at its best close to dawn, so skies will be dark. This is not a major shower, but it is consistent, producing 10 and even 20 meteors an hour, so if you spend even a half-hour looking, you’re likely to be rewarded.
Meteors appear in the sky year-round as earth collides with bits of interstellar ice, dust and debris that ignite as they streak through our atmosphere. However, meteor showers deliver more than a random burst, as they are caused by long trails of this cosmic flotsam following the wake of comets orbiting our sun. Unlike the more prominent meteor showers like the Leonids or the Perseids, the Delta Aquarids, the result of an unknown comet, were not recognized as an annual phenomenon until the 19th century. One meteor shower, the Geminids, is caused by a passing asteroid.
The Southern Delta Aquarids emanate from Aquarius, which by 3am is as high as it gets, 45 degrees above the southern horizon. Meteors will appear to shoot to the north, east and west of this radiant.
