The long and rambling Delta Aquariid shower is officially active from about July 12 to August 23 each year. The nominal peak is on July 28. There’s a waxing crescent moon up in early evening now. First quarter moon – a moon that sets around midnight – will come on July 27. In other words, this weekend and the coming week will offer us moon-free viewing from midnight until dawn. Then – as we move into early August – a wider waxing gibbous moon will fill up more hours of the night until full moon around the nights of August 2 and 3. A bright moon will be in the sky for this year’s Perseid meteor shower, peaking on the mornings of August 11, 12 and 13.
So heads up! This weekend, and the coming week, are a good time to watch for meteors in the peak hours before sunup, in a moon-free sky. Be sure to find a dark place to watch.
The Delta Aquariid shower favors the Southern Hemisphere, though is also wonderful from mid-northern latitudes. In years when the moon is out of the way, the broad maximum of this shower can be expected to produce 10 to 20 meteors per hour. But, even in early August, you’ll likely see some Perseids, too.
For the Delta Aquariids, as for most meteor showers, the best viewing hours are after midnight and before dawn for all time zones around the world.
How can I tell Perseid meteors from Delta Aquariid meteors? This is where the concept of a radiant point comes in handy. If you trace all the Delta Aquariid meteors backward, they appear to radiate from a certain point in front of the constellation Aquarius the Water Bearer, which, as viewed from the Northern Hemisphere, arcs across the southern sky. The radiant point of the shower nearly aligns with the star Skat (Delta Aquarii). The meteor shower is named in the honor of this star.
Meanwhile, the Perseids radiate from the constellation Perseus, in the northeast to high in the north between midnight and dawn. So – assuming you’re in the Northern Hemisphere – if you’re watching the Perseids, and you see meteors coming from the northeast or north … they are Perseids. If you see them coming from the south … they are Delta Aquariids. In a particularly rich year for meteors, if you have a dark sky, you might even see them cross paths! It can be an awesome display.
The Delta Aquariid meteors may tend to be a bit fainter than the Perseids and meteors seen in other major showers. That makes a dark sky free of moonlight even more imperative for watching the annual Delta Aquariid shower. About 5% to 10% of the Delta Aquariid meteors leave persistent trains, glowing ionized gas trails that last a second or two after the meteor has passed. The meteors burn up in the upper atmosphere about 60 miles (100 km) above Earth’s surface.
Rememeber, you never have to locate a shower’s radiant point to enjoy the meteors. However, it does help to have a dark night without moonlight. This year – in 2020 – the Delta Aquariids at their peak will be somewhat marred by a waxing gibbous moon, and August Perseids will be somewhat marred by the last quarter and wide waning crescent moon.
Delta Aquariid meteors may come from Comet 96P Machholz. Meteor showers happen when our planet Earth crosses the orbital path of a comet. When a comet nears the sun and warms up, it sheds bits and pieces that spread out into that comet’s orbital stream. This comet debris slams into the Earth’s upper atmosphere at about 90,000 miles (150,000 km) per hour, vaporizing – burning up – as meteors or shooting stars.
The parent body of the Delta Aquariid 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, Comet 96P Machholz has loomed as the primary candidate for being the Delta Aquariids’ 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 October 27, 2017, and will next come to perihelion on January 31, 2023.
Bottom line: The Delta Aquariid meteor shower lacks a very definite peak. It rambles along pretty steadily in late July and August, intermingling with the Perseids. The expected nominal peak happens in late July, and in 2020, comes a day or so after the first quarter moon on July 27. From any time zone, the best viewing window lasts for several hours, centered on roughly 2 a.m. (3 a.m. daylight saving time). Find an open sky away from artificial lights, lie down on a reclining lawn chair and look upward.
Bruce McClure has served as lead writer for EarthSky's popular Tonight pages since 2004. He's a sundial aficionado, whose love for the heavens has taken him to Lake Titicaca in Bolivia and sailing in the North Atlantic, where he earned his celestial navigation certificate through the School of Ocean Sailing and Navigation. He also writes and hosts public astronomy programs and planetarium programs in and around his home in upstate New York.