Early on Thursday morning (May 6), just before the eastern sky rises, we will have the opportunity to see some of the remains of the most famous comet briefly illuminate the early morning sky.
Halley’s Comet made its last passage through the inner solar system in 1986 and should not return until the summer of 2061. However, every time Halley sweeps around the sun, it leaves behind a dusty trail – call her “space litter” – which ends up behind the comet.
And as it turns out, Halley’s Comet’s orbit is close to Earth’s orbit in two places. One point is in the middle to the second part of October, resulting in a meteor display known as the Orionids. The other point comes in early May, producing Eta Aquarids.
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When and where to watch
Under ideal conditions (dark sky without moon), about 30 to 60 of these very fast meteors can be seen per hour at the peak of the display on May 6. The shower appears with about a quarter of the peak power for a few days before and after May 6. This year will be a very good year to watch for them, because the Moon will be in a waning crescent phase, only 28% illuminated and providing little interference for viewing these fast bands of light.
From places south of the equator, Eta Aquarids put on a very good show; Australians consider them their best meteor display of the year.
But for those looking north at the equator, this is a very different story.
What’s the point?
The radiant (the point of emission of these meteors) is in the “Water Jar” of the constellation Aquarius, which begins to rise above the eastern horizon at about 3 o’clock in the morning local summer time, but unfortunately never gets very high, as seen from the north temperate latitude. And shortly after 4 o’clock in the morning, dusk will begin to illuminate the sky.
So if you hope to see up to 60 meteors per hour, forget it; with the radiation so low above the horizon, most of these meteors will rise below the horizon and out of your sight.
In fact, from North America, typical Eta Aquarid speeds are only 10 meteors per hour at 26 degrees north latitude (Miami, Florida or Brownsville, Texas), five per hour at about 35 degrees latitude (Los Angeles or Cape Hateras, North Carolina) and practically zero north of 40 degrees (New York, Chicago and Philadelphia).
So, you might ask, “What’s the point of getting up before dawn to watch?” The answer is that you can still see something spectacular.
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Catch an earthling
For most, perhaps the best hope is to see a meteor coming out of the beam that will orbit the Earth’s atmosphere horizontally – like a bug flying over the side window of a car. Meteor watchers call such shooting stars “Earthlings.” They leave colorful, long-lasting paths that are extremely long and tend to embrace the horizon instead of shooting from above. They are also rarely numerous, but if you are lucky enough to notice only one or two, it will be useful to get up and go outside before the first light.
If you spot any of them early in the next few mornings, keep in mind that you’ll probably see an incandescent strip made of material from Halley’s Comet’s nucleus. When these tiny comet pieces collide with Earth, friction with our atmosphere lifts them to white heat and produces an effect popularly called “shooting stars.”
So, the shooting stars that we came to call Eta Aquarids are really an encounter with the traces of a famous visitor from the depths of space and from the dawn of creation.
Joe Rao serves as an instructor and guest lecturer in New York Hayden Planetarium. He writes about astronomy for Natural History Magazine,, Almanac of Farmers and other publications. Follow us on Twitter @Spacedotcom and onwards Facebook.