If you missed out on seeing Halley’s Comet in 1986, you’ll have an opportunity this week to see not the comet (it won’t return to the Sun’s vicinity until the summer of 2061), but bits and pieces of it. The orbit of Halley’s Comet very nearly intersects the orbit of the Earth at a portion in our orbit during the first week of May. Obviously, the comet is not there now, but the dusty debris left in the wake of previous apparitions of this famous comet flows along its orbit like a river of cosmic rubble.
When Earth passes through this region of space these tiny particles crash into our atmosphere at high speeds and are consumed in a fiery streak of light—a meteor, or “shooting star,” is the result.
The Eta Aquarid Meteor Showers
During the early morning of May 5th and 6th, in the predawn sky, will be the peak of the Eta Aquarid meteor shower, made up of tiny particles shed by Halley’s Comet. It’s usually the year’s richest meteor shower for Southern Hemisphere observers, but north of the equator it’s one of the more difficult annual displays to observe.
From mid-northern latitudes, the radiant (from where the meteors appear to emanate) rises about 1:30 a.m. local daylight time, scarcely two hours before morning twilight begins to interfere. At peak activity, from latitude 26-degrees north—that’s around Brownsville, Texas, or the Florida Keys – about a dozen shower members can be seen per hour by a single observer with good sky conditions. But that number falls to practically zero north of latitude 40-degrees.
But don’t give up hope, for you still might want to check out the sky for the chance at sighting a very special kind of meteor: an Earthgrazer.
What is an Earthgrazer?
Earthgrazers are meteors that skim the top of Earth’s atmosphere like a stone skipping across the surface of a pond. They appear when the radiant of a meteor shower is near the horizon, spewing meteoroids not down, but horizontally overhead.
But Earthgrazers are rare. An hour’s watching might produce no more than one or two at most, but that’s plenty. Earthgrazers are colorful and gracefully slow. People who are lucky enough to see one talk about it for years. Looking for Earthgrazers is simple: Spread a blanket on the ground, lie down and look up. A reclining lawn chair facing southeast works just as well. Eta Aquarid Earthgrazers streak overhead, flying generally southeast to northwest.
The Eta Aquarids are considered to be the best meteor shower of the year—if you live in the Southern Hemisphere. Up in our latitudes, the constellation of Aquarius remains very low in the sky at the break of dawn, so you likely would not see more than a handful of shooting stars.
Of course, the “draw” of the Eta Aquarids is that they are the dross or “junk” left behind by Halley’s Comet. So if you see any of these meteors, you can at least say that you sighted pieces of Halley that broke off its nucleus from one of its previous visits to the solar system!
What’s In Store for 2020?
The swift Eta Aquarid meteors follow paths that seem to spray out from a point near the star Eta in the constellation Aquarius the Water Carrier, which lies low to the east-southeast horizon at the break of dawn.
William Tyler Olcott (1873-1936), an American lawyer and amateur astronomer, characterized them as “streak-leaving meteors” because the brightest ones often have persistent trains. Unfortunately, this year the Moon will be heading toward the full phase (on the 7th) and thus very bright on the morning of May 6th, the predicted date of shower maximum. But the display lasts several weeks, and observers who arise just before dawn on the first few mornings of the month will have a chance to view a dozen or more Eta Aquarids per hour.