All you need to know: Eta Aquariid meteors

Full moon will be May 7. That means there’s an exceedingly narrow window of true darkness between moonset and dawn now. Monday and/or Tuesday morning will be the peak mornings of the Eta Aquariid meteor shower. The meteors will be flying, but moonlight will interfere.

Meteor dropping straight down from a triangular-looking star pattern, with a Saguaro cactus in the foreground.

Eta Aquariid meteor coming straight from its radiant point – the Water Jar asterism in the constellation Aquarius, visible in the top left of this photo – captured by Eliot Herman in Tucson, Arizona on May 4, 2020. Thank you, Eliot!

In 2020, the forecast calls for the greatest number of Eta Aquariid meteors to fall before dawn on (or near) May 5. However, this shower has a rather broad maximum, so just as many meteors may be flying on the mornings before and after. There is one big bugaboo for watching the Eta Aquariids in 2020, though. The shower will have to contend with a nearly full waxing gibbous moon. That’s why we’ve been recommending you try watching for meteors before sunup on May 1, 2 and 3. Fewer meteors will be flying then, but there will be a larger moon-free window between moonset and dawn.

Want to try watching the Eta Aquariids in moonlight on the mornings of May 4 and 5? Here are some tips:

1. Sprawl out in a moon shadow. Notice that the moon casts shadows. Find a moon shadow somewhere that still provides you with a wide expanse of sky for meteor-viewing. A plateau area with high-standing mountains to block out the moon would work just fine. If you can’t do that, find a hedgerow of trees bordering a wide open field (though obtain permission, if it’s private land). Or simply sit in the shadow of a barn or other building. Ensconced within a moon shadow, and far from the glow of city lights, the night all of a sudden darkens while the meteors brighten.

2. Avoid city lights. We know you know this, but just a reminder. A wide open area – a field or a lonely country road – is best if you’re serious about watching meteors. Visit EarthSky’s Best Places to Stargaze to find a dark location near you.

3. Watch with a friend or friends, and try facing in different directions so that if someone sees a meteor, that person can call out “Meteor!” to the rest.

4. Notice the speed and colors, if any, of the meteors.

5. Watch for meteor trains. A meteor train is a persistent glow in the air left by some meteors after they have faded from view. Trains are caused by luminous ionized matter left in the wake of this incoming space debris. Hard to see in the moonlight, but watch for them!

6. Embrace the moon. We hear people bubble with excitement about seeing meteors in all sorts of conditions – moon or no moon – city lights or no city lights. And so, this week, try taking your lawn chair or blanket to a wide open location and bask in the moon’s bright light. You’ll see an occasional meteor streak by. It’ll be beautiful!

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Many short, bright radial streaks indicating meteor pathways, with  glowing moon over desert horizon.

The 2013 Eta Aquariid meteor shower was fantastic as viewed from Earth’s Southern Hemisphere. Colin Legg of Australia created this composite of his experience. He wrote, “Composite of approximately 50 images containing 26 meteors, meteor train, 17% moon, zodiacal light and Pilbara desert.”

Very bright meteor streak against Milky Was, above misty valley in crater of mountain.

Meteor captured over Mount Bromo, an active volcano in Indonesia, during the 2013 Eta Aquariid shower. Photo by Justin Ng of Singapore. See more photos by Justin Ng.

The Eta Aquariid meteor shower favors the Southern Hemisphere; it ranks as one of the finest showers of the year there, in a year when the moon isn’t obscuring the show. 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.

Why more Eta Aquariid meteors in the Southern Hemisphere?

Be aware that the Eta Aquariid shower extends on either side of its peak morning of May 5, 2020. Writing for the International Meteor Organization in 2017, veteran meteor expert Robert Lunsford pointed out:

… There is no sharp peak for this shower, but rather a plateau of good rates that last approximately one week centered on May 6.

So, in 2020, we stand by our hope that some meteors will be flying in the early morning hours prior to the peak. But, of course, you never know.

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 moonset 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.

Sky chart of radiant point of Eta Aquarid meteor shower in the constellation Aquarius.

Radiant point of Eta Aquariid meteor shower. It’s in the constellation Aquarius, in the southeast before dawn on May mornings, as seen from mid-northern latitudes.

Sky chart of constellation Aquarius with Water Jar marked.

A Y-shaped asterism called the Water Jar marks the radiant of the Eta Aquariid meteor shower. It’s noticeable, if your sky is dark.

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 – trillons 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.

Comet, bright head and cone-shaped tail against star field.

Halley’s comet, the parent of the May Eta Aquariid and October Orionid meteor showers. Dust from this comet will streak the nighttime as Eta Aquariid meteors on the mornings of May 5 and 6. Image via NASA Blueshift.

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 kilometers 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. This year, 2020, a nearly full waxing gibbous moon interferes with the peak on the mornings of May 4 and 5.

EarthSky’s meteor shower guide for 2020

Bruce McClure