It might seem to you as if meteor showers are one-night affairs, and, it’s true, there’s usually one late night or early morning that’ll provide the best show. But most meteors in annual showers rain down over many days, or even weeks. In 2021, the forecast for May’s Eta Aquariid shower calls for the greatest number of meteors to fall before dawn on Wednesday, May 5. The mornings around that date – May 4 and 6 – might give you a good sprinkling of meteors as well. Note phase of the moon. There’s more moon on the morning of May 4 than May 5. In 2021, on the mornings of May 5 or 6, we don’t expect the light of a waning crescent moon – rising near the time of dawn – to intrude too greatly. The moon might even add a little something to your early-morning meteor drama, as it joins up with the bright morning planets, Jupiter and Saturn, on May 4 and 5. See the chart below:
The Eta Aquariid meteor shower favors the Southern Hemisphere; it ranks as one of the finest showers of the year there. At mid-northern latitudes, these meteors don’t fall so abundantly, although people in the southern states in the U.S., for example, tend to see more meteors than those at more northerly latitudes.
In a dark sky – when the moon is down – especially at more southerly latitudes, the Eta Aquariids can produce up to 20 to 40 meteors per hour. From mid-northern latitudes, you might only see about 10 meteors per hour.
In general, the best time to watch these fast and often bright meteors is in the hour or two before the onset of morning twilight. Don’t know when twilight begins in your part of the world? Visit Sunrise Sunset Calendars and remember to check the astronomical twilight box.
Want to know the time of moonrise in your area? Visit Sunrise Sunset Calendars, and check the moonrise and moonset box, to find out when the moon sets in your sky.
Give yourself at least an hour of viewing time for watching any meteor shower. Meteors tend to come in spurts that are interspersed by lulls. Also, it can take as long as 20 minutes for your eyes to adapt to the dark.
You need no special equipment to watch a meteor shower, but a little luck always helps. Find a dark, open sky away from artificial lights, and sprawl out on a reclining lawn chair. Meteor watching is a lot like fishing. Sometimes you catch a good number of them, and sometimes you don’t.
Radiant point of the Eta Aquariid shower. If you trace the paths of the Eta Aquariid meteors backward, they all seem to radiate from a certain point in front of the constellation Aquarius the Water Bearer. This point on the sky’s dome is called the radiant of the meteor shower, which nearly aligns with the faint star Eta Aquarii. Hence, this meteor shower is named in honor of this star.
Eta Aquarii is one of the four stars making up the Y-shaped Water Jar asterism in the northern part of Aquarius. If you can find the Water Jar in the constellation Aquarius, you’ve as good as located the radiant point for the Eta Aquariid meteors. The alignment of the radiant and the star is of course coincidental. Eta Aquarii is some 170 light-years away – trillions upon trillions of miles away – while the Eta Aquariid meteors burn up about 60 miles (100 km) above Earth’s surface.
Meteor shower radiants are sometimes misunderstood by casual meteor-watchers. You don’t need to know where they are to watch a meteor shower. That’s because the meteors fly every which way across the sky, in front of numerous constellations. However, the higher a shower’s radiant appears in your sky, the more meteors you’re likely to see. For the Eta Aquariids, the radiant soars highest in the nighttime sky just before dawn. That’s why you can expect to see the most meteors in the wee morning hours.
You can see some Eta Aquariid meteors in late evening, before the radiant rises into your sky. In fact, late evening is the best time to see earthgrazers, meteors that make exceptionally long streaks across your sky. As the radiant rises higher – that is, as the hours of the night tick away to dawn – you’ll see shorter meteors, but more meteors.
Halley’s comet is the source of the Eta Aquariid meteor shower. Every year, our planet Earth crosses the orbital path of Halley’s comet in late April and May, so bits and pieces from this comet light up the nighttime as Eta Aquariid meteors. This shower is said to be active from April 19 to May 20, although Earth plows most deeply into this stream of comet debris around May 5 or 6.
The comet dust smashes into Earth’s upper atmosphere at nearly 150,000 miles per hour (240,000 km per hour). Roughly half of these swift-moving meteors leave persistent trains – ionized gas trails that glow for a few seconds after the meteor has passed.
Our planet also crosses the orbital path of Halley’s comet at the other end of the year, giving rise to the Orionid meteor shower, which is usually at its best in the predawn hours on or near October 21.
Bottom line: What’s a good meteor shower for the Southern Hemisphere? It’s usually the Eta Aquariid shower. We in the Northern Hemisphere can see this shower, too, peaking on the morning of May 5, 2021. If you’re clouded out that morning, try May 6.
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.