If you’ve looked in a dark this week, you might have seen some of these meteors, although we’re hearing that they’ve been sparse so far. In 2017, the forecast calls for the greatest number of Eta Aquariid meteors before dawn on May 5 or 6. The moon is in a waxing gibbous phase and will set in the wee hours after midnight. This shower favors the Southern Hemisphere, ranking as one of their finest showers of the year. At mid-northern latitudes, these meteors don’t fall so abundantly – and twilight is long and so interferes at northerly latitudes – but mid-northern meteor-watchers who try will likely catch some Eta Aquarids, too. Follow the links below to learn more about the Eta Aquariid meteor shower.
When and how should I watch the Eta Aquariids? The 2017 Eta Aquariid meteor shower is expected to produce the greatest number of meteors in the wee hours before dawn on May 5 and 6. However, the broad peak of the Eta Aquariid shower may present a decent showing of meteors during the predawn hours on May 4 and May 7, too. And in fact the shower extends much beyond these dates on either side. Writing for the International Meteor Organization on May 1, 2017, 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.
In fact, Lunsford recommended watching earlier in the week, to avoid the moon. Whether you have tried that – or plan to watch closer to the peak – you’ll want to keep an eye on moonset times. A waxing gibbous moon will shine in the sky during the shower’s peak. On the peak mornings, the moon is setting a few hours before dawn, leaving a window for meteor-watching. But the moon is now setting later each morning, interfering more and more with the shower. For this reason, for example, the morning of May 5 might be a better time to watch than the morning of May 6. Click here, and check the moonrise and moonset box, to know when the moon rises and sets in your sky.
In general, the best time to watch these fast and often bright meteors is in the early morning hours, before the onset of morning twilight. Don’t know when twilight begins in your part of the world? Try one of the links on our almanac page.
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. 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 Aquarid 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 Aquarid 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 Aquarid 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 Aquarids, 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 Aquarid 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.
No special equipment is needed to watch a meteor shower. Find a dark, open sky away from artificial lights, and sprawl out on a reclining lawn chair.
How many meteors should I expect to see? In a dark sky, especially at more southerly latitudes, the Eta Aquarids can produce up to 20 to 40 meteors per hour. From mid-northern latitudes, you might only see about 10 meteors per hour. Or you might see more.
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 Aquarid 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 240,000 kilometers (150,000 miles) 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.
Why not see how many Eta Aquarid meteors you’ll catch in the dark hours before dawn on May 5 and 6?
Bottom line: What’s a good shower for the Southern Hemisphere? In 2017, it’s the Eta Aquariid shower on the mornings of May 5 and 6. It’s possible to see some Eta Aquariids in the Northern Hemisphere, too, but the farther south you live in the Northern Hemisphere, the better! How to watch, some history, chart showing radiant point in this post.
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.