for National Geographic News
The South Delta Aquarids top the bill of several meteor showers converging in the night sky this week, giving night owls good reason to stay up after the moon sets to catch an eyeful of shooting stars.
"They're the strongest of several low-key showers, the combined activity of which makes the last week of July a productive time," said Neil Bone, director of the British Astronomical Association's meteor section.
Peak rates for the South Delta Aquarids top out in the early morning of July 28 at around a dozen shooting stars per hour for viewers in North America and Europe. Rates are higher in southern latitudes.
Lew Gramer is a Cambridge, Massachusetts-based amateur astronomer who maintains a popular meteor-observation mailing list for the North American Meteor Network. He said the activity from several other simultaneous showers could bring rates to between 25 and 30 shooting stars per hour.
The other showers include the South Iota Aquarids, North Delta Aquarids, Alpha Capricornids, Pisces Austrinids, and even a few early Perseids, which peak on the dark-moon night of August 12.
"Not just the SDAs [South Delta Aquarids], but these lesser showers as well, and other meteors which come from no known shower at all—so-called sporadics—all contribute to that upper bound of 25 to 30 meteors," Gramer said.
According to Bone, the Alpha Capricornids in particular could treat observers to the pleasing sight of long, slow, and bright meteors.
Observing the Show
Robert Lunsford, operations manager for the American Meteor Society, laments the bright moon will swamp many of the faint shooting stars at the end of July. Favorable conditions for viewing the South Delta Aquarids return in 2006.
For the determined, however, he offers this advice:
"Wait until the moon is low in the west or beneath the horizon. On July 27, with the moon only four days before full, the moon will set an hour or two before the start of morning twilight [on July 28], depending on one's latitude. This would be the best time to try to see any activity."
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