Sunday, July 28, 2013

Delta Aquarid meteor shower peaks tonight

Comet 96P Machholz, the possible parent of the Delta Aquarid meteor shower, was discoverd on May 12, 1986, by Donald Machholz. Photo: Wikimedia Commons

The Delta Aquarid meteor shower is predicted to be at its best during the wee hours before dawn on Monday, July 29, and Tuesday, July 30, 2013. The most favorable viewing window is from about 1 a.m. (2 a.m. Daylight Saving Time) until the onset of morning dawn. These viewing times apply to all time zones around the world. Although this shower is visible from both the Northern and Southern Hemispheres, it tends to favor the more southerly latitudes. North of the equator, it’s better seen in the tropical and subtropical regions rather than farther north. This is a long, rambling shower that’ll stretch out for weeks beyond the peak, combining with the Perseid meteor shower peak on August 11-13. So if you miss the shower tonight, keep watching!

Just one caveat tonight, but it’s a big one. We’ll have a waning gibbous moon or last-quarter moon on the peak nights of the Delta Aquarid shower. Try your luck watching these meteors anyway, starting at late evening or around midnight – or before the moon rises into the night sky. In the Southern Hemisphere, especially, there could be a few dark hours of viewing before moonrise. The radiant for this shower climbs above the horizon at an earlier hour at more southerly latitudes – and what’s more, the moon rises later at more southerly latitudes.

The Great Square of Pegasus can point you to the constellation Aquarius and the Delta Aquarid meteor shower peak. Copyright: Earthsky Communications Inc.
The Great Square of Pegasus can point you to the constellation Aquarius and the Delta Aquarid meteor shower peak. Copyright: Earthsky Communications Inc.

Unless you live in the far northern part of the globe – where there is little or no nighttime at this time of year – mid-northern latitudes can expect some viewing time before dawn, though in moonlit skies. Around the world, the planets Jupiter and Mars adorn the eastern predawn sky, and the planet Mercury rises in the east just as darkness gives way to dawn.

The Delta Aquarid shower is, at best, a modest shower, offering perhaps 15 meteors per hour. About five to ten percent of these relatively faint, medium-speed meteors leave persistent trains – glowing ionized gas trails that last a second or two after the meteor has passed.

The parent body of the Delta Aquarid meteor is not known with certainty. It was once thought to have originated from the breakup of what are now the Marsden and Kracht sungrazing comets. More recently, the Comet 96P Machholz has loomed as the primary candidate for being the Delta Aquarids’ parent body.

Donald Machholz discovered this comet in 1986. It’s a short-period comet whose orbit carries it around the sun once in a little over five years. At aphelion – its greatest distance from the sun – this comet goes out beyond the orbit of Jupiter. At perihelion – its closest point to the sun – Comet 96P Machholz swings well inside Mercury’s orbit. Comet 96P/Machholz last came to perihelion on July 14, 2012 and will next come to perihelion on October 27, 2017.

Credit: earthsky.org

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