When asked to name a comet, chances are people will name Halley's and, in most cases, won't remember any others. Tonight, the Eta Aquarid meteor shower will rain bits of the solar system's most famous comet down on Earth as part of the yearly demonstration to remind us that even though we may not be able to see Halley's comet, it is still above streaking through the heavens.
The shower will be best viewed tonight and in the early hours of tomorrow with skywatchers being able to see some of the "comet litter" zipping through our atmosphere in the form of meteors.
Under ideal conditions, about 40 of these meteors can usually be seen shooting across the night sky per hour. While viewing will be best tonight and early in the morning, the shower will appear at about one-quarter strength for three or four days after May 6 as well.
Unfortunately, this year there are two drawbacks if you planned on staying up late to catch a glimpse of Halley's garbage lighting up the atmosphere. First, the moon will be bright. It was full on Sunday and although it is now waning, it will still be rather bright and will likely block from view many of the fainter meteors streaking through the atmosphere.
The other drawback only applies to those watching from north of the equator. The emanation point of these meteors is at the "Water Jar" of the constellation Aquarius, which appears above the southeast horizon around 3 a.m. and never gets very high as seen from the north temperate latitudes, meaning the actual observed rates are much lower than the 40 per hour.
For most people gazing at the heavens in search of these meteors, the best hope of catching a glimpse of them is when the meteors emerge from the radiant and skim the atmosphere horizontally. Meteor watchers call these types of shooting stars "Earthgrazers" and they leave a colorful, long lasting trail as they streak across the sky.
"These meteors are extremely long," said Robert Lunsford, of the International Meteor Organization. "They tend to hug the horizon rather than shooting overhead where most cameras are aimed."
Bill Cooke, a member of the Space Environments team at the Marshall Space Flight Center, said, "Earthgrazers are rarely numerous. But even if you only see a few, you're likely to remember them."
If you do sight these meteors, keep in mind that what you are seeing is being produced by material that originated in the nucleus of Halley's Comet. When these tiny bits of the comet collide with the atmosphere of the Earth, friction raises them to a white heat and produces the effect known as "shooting stars."
Halley's Comet travels around the sun in an elliptical orbit that takes it out beyond Neptune and as close as inside the orbit of Venus. This journey takes the comet about 75 years to complete and is the only comet that is visible to the naked eye. Halley's last visit to Earth occurred in 1986 and it is set to make its grand return in the summer 2061.