As August approaches, sky-watchers are in for month after month of spectacular celestial events. Meteor activity is ramping up, and the Southern Delta Aquariid shower will kick it off this weekend.
Earth is currently traveling through multiple clouds of dusty comet debris, bringing a higher-than-usual amount of meteors to the night sky. When these fragments of rock and metal enter the atmosphere, the air around them heats up, creating a blazing glow visible from the ground. The Delta Aquariids coincide with a few other meteor showers, such as the famous Perseids, that promise to impress spectators for weeks to come.
The Delta Aquariids bring breathtaking meteors—also called shooting stars—that streak through the sky at roughly 25 miles per second. While the shower lasts from roughly July 18 to August 21, it will peak on July 30, with high activity on the nights immediately before and after. A small fraction of the meteors—about 5 to 10 percent—leave behind trails of glowing ionized gas that stick around for a few seconds after the fireball has gone.
While the Southern Delta Aquariids favor observers in the southern tropics, people in the United States can still watch—Americans at lower latitudes, however, will have the best view.
Viewing conditions this year
Under a dark sky with no interference from the moon, the spectacle can bear 15 to 20 meteors per hour. But unfortunately, viewing conditions for the peak this weekend are going to be less than ideal—the moon will be more than 90 percent full in advance of Tuesday’s “Sturgeon Moon,” which also happens to be a brighter-than-usual supermoon.
While the full moon will make for gorgeous lunar viewing next week, it’s the opposite of what you want for a meteor shower. Moonlight brightens the sky, making it more difficult to glimpse the meteors’ glow. But here’s a tip: Try viewing in the early hours of the morning, after the moon has set.
Or, since this shower doesn’t have as noticeable a peak as others—it sort of “rambles along steadily from late July through early August,” as EarthSky writes—you could try viewing the meteors a few days before the peak, when the moon will be slightly less full.
How to find the meteors
As a rule of thumb, the best advice for viewing meteor showers is getting to the darkest sky possible. Like the moon, artificial light will obscure your view and cause shooting stars to appear more faint. Observing from a designated dark sky area, or anywhere away from the glow of cities, will maximize your chance of seeing the most meteors. “The more stars you can see, the more meteors you can see,” Robert Lunsford, the secretary-general of the International Meteor Organization, told the New York Times’ Adam Mann last year. And keep your eyes off your phone screen—it can ruin your night vision.
In this event, the shooting stars appear to radiate from Aquarius, the “water bearer” constellation, which, along with the star Delta Aquarii, gives the shower its name. Aquarius appears in the dark southern sky, located between the constellations Capricornus and Pisces. The bright star Fomalhaut, in the “southern fish” Piscis Austrinus, can direct your eye the right way. Aquarius—and, as a result, the meteors—will be highest in the sky around 2 a.m. local time, and the best viewing is around 3 a.m.
Though Aquarius appears to be the source of the meteors, the Delta Aquariid shower is actually caused when the Earth passes through a cloud of debris in space, likely left by Comet 96P/Maccholz. The ball of rock, dust and ice is a short-period comet that orbits the sun once every five or so years, and it spans about four miles across—or just over half the size of the object thought to have wiped out the dinosaurs, per NASA.
A trio of showers
The Southern Delta Aquariid shower is just one of three prominent celestial shows that will light up skies this weekend. It will be accompanied by the famed Perseids, which are building to a spectacular peak that could boast roughly 100 meteors per hour on August 13 (and viewing conditions will be nearly perfect). For now, though, observers might see only a small handful of Perseids per hour. Any meteors this weekend that appear to emanate from the north or northeast—the opposite side of the sky from the Delta Aquariids—are probably early Perseids.
The other shower, called the Alpha Capricornids, is a weak show that also peaks the night of July 30. This one tends to produce fewer than five slow-moving meteors each hour, but it’s notable for its exceptionally bright fireballs. The Alpha Capricornids can be seen anywhere in the sky. Though right now, as meteor showers go, this event is not so impressive, some astronomers have predicted that by 2220 to 2420, the Alpha Capricornids will become stronger than any meteor shower currently known.