It has been 38 years since Halley's Comet last passed through the inner solar system. This famous comet takes roughly 75 years to circle the sun. But if you're 42 years old or younger, you probably have little or no memory of the 1986 appearance of this famous cosmic vagabond (your next chance will come in the summer of 2061).
Or maybe, if you were around back then, you didn't see Halley at all because of light pollution or the comet's low altitude above the horizon. If you missed out on the 1986 event, or don't want to wait until 2061, you might want to step outside before sunrise during these next few mornings and try to catch a view of some "cosmic litter" that has been left behind in space by Halley's Comet.
The orbit of Halley's Comet closely approaches the Earth's orbit at two places. One point is in the middle to latter part of October, producing a meteor display known as the Orionids. The other point comes in the early part of May, producing the Eta Aquarid meteors.
Related: Meteor showers 2024: When is the next one?
When and where to watch
This year, the Eta Aquarid meteor shower is predicted to be at its best on Sunday morning, May 5, when the moon is a very thin (8% illuminated) waning crescent and safely out of harm's way to cause any disruption to visibility.
This mid-spring meteor display remains above one-quarter of its peak strength for about 10 days. And the 2024 version of this shower is also anticipated to provide a higher number of meteors than usual. More on that in a moment.
This is the best meteor shower of the year for those living in the Southern Hemisphere, typically yielding hourly rates of 60 or more.
There is, however, a bit of a drawback if you plan to watch for these meteors from north of the equator. The radiant (the point from which these meteors appear to originate in the sky) is found at the "Water Jar" asterism of the constellation Aquarius, which comes above the southeast horizon at around 3 a.m. local daylight time, and never gets very high as seen from north temperate latitudes.
That means the actual observed rates are usually lower than the oft-quoted 60 per hour; closer to 10 to 20 per hour at around latitude 40-degrees north (Philadelphia) to perhaps 20 to 40 per hour near latitude 25-degrees north (Brownsville, TX).
Enhanced activity in 2024?
According to the 2024 Observer's Handbook of the Royal Astronomical Society of Canada, this year's Eta Aquarids are "expected to show a noticeable outburst" from meteoroids ejected from Halley's comet about 2,500 years ago.
In a technical paper published in the August 11, 2020 issue of the journal Astronomy & Astrophysics, astronomer Auriane Egal and four colleagues from the University of Western Ontario, present a new numerical model of the Eta Aquarid and Orionid meteor showers (referred to in the paper as the "Halleyids" meteor showers).
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According to Dr. Egal and her colleagues, material that was shed by Halley's Comet, primarily in 983 B.C., with several smaller particle ejections from the 1058 B.C., 835 B.C. and 314 B.C. comet apparitions, augmented by close interactions of these meteoroids with the gravitational pull of Jupiter, should lead to enhanced Eta Aquarid activity in 2024.
Earth is expected to pass closest to this "rubble river" at around 13:30 UT on May 5. Unfortunately, it will be daylight over Europe and North America, but it is hoped that noticeable enhanced activity might last for perhaps a few days on either side of this predicted peak.
The number of meteors that may be seen might be as much as two or three times the normal rate for the 2024 Eta Aquarids. In their paper, Egal et al write that this year's outburst could produce "from 120 to 160 meteors per hour, with a 30% confidence on the predicted rates."
Catch an Earthgrazer
For most who live at mid-northern latitudes, perhaps your best hope is not necessarily to see a large number of meteors, but rather to catch a glimpse of a meteor emerging from the Eta Aquarid radiant that will skim Earth's atmosphere horizontally — much like a bug skimming the side window of an automobile. Meteor watchers call such shooting stars "Earthgrazers." They tend to leave colorful, long-lasting trails.
"These meteors are extremely long," says Robert Lunsford, of the International Meteor Organization. "They tend to hug the horizon rather than shooting overhead where most cameras are aimed."
"Earthgrazers are rarely numerous," cautions Bill Cooke, a member of the Space Environments team at the Marshall Space Flight Center. "But even if you only see a few, you're likely to remember them."
With the prediction of enhanced activity on the table for Sunday (May 5), you might have a better chance of seeing more than a few Earthgrazers in the hour or two prior to the first light of dawn. If you plan to look, try settling down on a long lounge or deck-chair, dress warmly and concentrate on that area of the sky from overhead and down toward the southeast. Consider also trying again on Monday morning (May 6) if your local skies are clear.
Comet crumbs
If you do catch sight of an Earthgrazer early on those mornings, keep in mind that you'll likely be seeing the incandescent streak produced by material which originated from the nucleus of Halley's Comet. When these tiny comet crumbs — likely no larger than a grain of sand or a pebble — collide with Earth, friction with our atmosphere raises them to white heat and produces the effect popularly referred to as "shooting stars."
So it is that the shooting stars that we have come to call the Eta Aquarids are really an encounter with the traces of a famous visitor from the depths of space and from the dawn of creation.
Editor's note: If you snap an amazing Eta Aquarid meteor shower photo that you'd like to share with us and our news partners for a possible story or image gallery, send images and comments to us at spacephotos@space.com.
Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for Natural History magazine, the Farmers' Almanac and other publications.
