Late July 2019 – around July 28 – presents the nominal peak of the Delta Aquariid meteor shower. But don’t let that date thwart you, if you have a chance to be in a dark place for meteor-watching, anytime in the coming weeks. The long and rambling Delta Aquariid shower is officially active from about July 12 to August 23 each year. The coming new moon on July 31/August 1 (depending on your time zone) means lovely waning crescents in the optimum predawn hours in late July. It means dark skies throughout most of the night all through the first week of August.
The Delta Aquariid shower favors the Southern Hemisphere, though is still visible 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. This shower overlaps with the more famous Perseid meteor shower, which in early August is rising to its peak (this year on the mornings of August 11, 12 and 13, unfortunately under the light of a bright moon). Those who observe the Perseids are likely to see some Delta Aquariid meteors flying on the same nights.
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 five to ten percent 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 2019 – the prospects for watching the Delta Aquariids in late July and early August are very good, with little moonlight to ruin the show.
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, coinciding with the Perseids. The nominal peak is in late July, shortly before the new moon on August 1, 2019. 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.