The Delta Aquarid shower will appear to radiate from a point in the sky in the zodiac constellation Aquarius about two outstretched fists above Fomalhaut, the sole bright star in the southern sky at the time. The map shows the sky facing south at 2 a.m. Created with Stellarium
Wahoo! It’s that time of year again. Meteor showers are back on the menu beginning with the southern Delta Aquarids which peak Tuesday morning July 30. This long-duration shower begins around July 14 and finally peters out more than a month later on Aug. 18. Tuesday morning we might see between 15-20 meteors per hour.
Southern Delta Aquarid meteor caught on video in 2009 by astrophotographer John Chumack
The Delta Aquarids radiate from low in the southern sky as seen from mid-northern latitudes. A low radiant means many of a shower’s meteors are out of view, streaking away below the horizon. Expect lower counts if you live in the northern half of the U.S. , Canada and Europe. Most of the Delta Aquarids will shoot north, east and west from the constellation Aquarius. The farther south your location then, the more meteors you’ll see.
The Delta Aquarids make for a consistent shower even if the numbers for northerners aren’t particularly good. Lest you lose heart, we experience the same situation every May with the Eta Aquarid meteor shower. Despite the radiant’s location low in the east at the start of dawn, that stream put on a fine show this past May with a volley of memorable Earth grazers.
I got lucky once and caught a portion an Earth-grazing Leonid meteor trail during the November 2009 shower. The trail was white to my eye but shows up green in the photo. I suspect the color comes from oxygen atoms that were ionized or “excited” by the meteor’s passage in the upper atmosphere. Credit: Bob King
Earth grazers are meteors that strike the Earth’s atmosphere at a very shallow angle, coming up from below the horizon and vaulting across more than half the sky. They’re more likely to be seen when the meteor radiant is near or below the horizon. Keep an eye out for them Tuesday morning.
It’s takes fortitude to catch a meteor shower during the work week, but I plan to be out there and hope you will too. To see the bestest, mostest meteors, find a dark location with a good view to the south. Set up a comfortable lounge chair facing south-southeast and plan to watch between about 1 a.m. and dawn. If you wanted to limit your sleep sacrifice to one hour, go for 3-4 a.m. This is when the radiant will be highest in the south just before dawn.
Be aware the last quarter moon, located well off to the east in Aries, will brighten the sky enough to compromise the fainter meteors. As you kick back, you’ll see gritty bits of Comet 96P/Machholz flash to incandescence above. Comets shed dust and small rocks as they round the sun on repeated trips to the inner solar system.
Comet 96P/Machholz, discovered by amateur astronomer Don Machholz on May 12, 1986 is the comet responsible for the southern Delta Aquarid meteor shower. Credit: NASA
When Earth’s orbit intersects the stream of debris, as it does every summer with Machholz, we smack right into the grit, which vaporizes in a streak of light called a meteor. The Delta Aquarids hit the atmosphere at around 90,000 mph (145,000 km/hr), which sounds and is incredibly fast, yet that about average for a meteroid entry.
The northern Delta Aquarids (July 16 – Sept. 10), Alpha Capricornids (July 15 – Aug. 10) and several other minor showers active at the same time as the southern Delta Aquarids add even more spice to late July and August nights.
Like a fireworks display that ends in a grand finale, the Perseid shower will cap off the show on August 12-13 with 60-100 meteors per hour and no moon to interfere. Happy hunting!