While the Orionid meteor shower in October is famous as being from the tail of the renowned Halley’s comet, Earth actually passes through this tail twice each year, and we are in the middle of it now.
It truly is the Age of Aquarius, at least this weekend. For the streaks of light known as the Eta Aquarid meteor shower, which comes in early May every year, appear to emanate from that very constellation.
The shower is set to peak in the pre-dawn of May 5, astronomers say, with as many as 20 to 40 meteors hourly, though that depends on one’s latitude. Most of the action will be in the Southern Hemisphere, but the shower could surprise up north too. Unlike the Lyrid meteor shower on Earth Day, the Eta Aquarids will not be upstaged by moonlight, since our satellite is in its dimmer, waning crescent phase. (Related: Lyrid Meteor Shower Graces Pre-Dawn Earth Day Sky)
“This year the peak will occur on the night of May 5 about 9 p.m. EDT with meteor rates of about 30–40 meteors per hour near peak,” said NASA in a media release. “Eta rates will also be good on the evening of May 4.”
Halley itself, perhaps the most famous comet in history, passes through our field of vision once about every 75 years. Having last swung by in 1986, it will not be visible to us again until 2061, Space.com tells us. However, it still is orbiting the sun, and it is such a massive comet that it leaves behind a trail of debris both coming and going. This gives us the Eta Aquarids in May and the Orionids in October. (Related: Peaking Orionid Meteors Give Spectacular Show October 20–21 and Orionid Meteor Shower and the Great Leader Tecumseh)
Several characteristics set the Eta Aquarids apart from other meteors. Their speed, for one: They slam into Mother Earth’s atmosphere at about 66 kilometers per second (40 mps), at the upper part of the 10–70 km per second average for meteors. Moreover, they tend to hit at a shallow angle, skimming the upper atmosphere rather than falling straight down. The ones that do this are known as earthgrazers, and even one can produce quite a show.
“The Etas contain quite a few fireballs,” NASA said in its statement.
“Earthgrazers are meteors that skim horizontally through the upper atmosphere,” says Spaceweather.com. “They are slow and dramatic, streaking far across the sky. The best time to look for earthgrazers is between 2:00 to 2:30 a.m. local time when Aquarius is just peeking above the horizon.”
Unfortunately the farther north one is, the fewer shooting stars you’ll see.
“In fact, from North America, typical Aquarid rates are only 10 meteors per hour at 26 degrees north latitude (Miami, Fla., or Brownsville, Texas), 5 per hour at around 35 degrees latitude (Los Angeles, Calif., or Cape Hatteras, N.C.) and practically zero to the north of 40 degrees (New York, Chicago, and Philadelphia),” reports Space.com.
But the earthgrazers could wow, if a stargazer is lucky enough to glimpse one. And NASA will webcast a live video/audio feed of the Eta Aquarid shower on the night of May 5–6, 2013 via the Marshall Space Flight Center Ustream feed. For those who want to look in person, EarthSky.org describes in detail how to spot the point in Aquarius that the meteors appear to radiate from.
"These meteors are extremely long," Robert Lunsford of the International Meteor Organization told Space.com of earthgrazers. "They tend to hug the horizon rather than shooting overhead."
And what they lack in quantity, they make up for in quality.
"Earthgrazers are rarely numerous," NASA meteor expert Bill Cooke has said, according to Space.com. "But even if you only see a few, you're likely to remember them."