for National Geographic News
In the coming days and weeks, the trainedor perhaps luckyobserver will be able to step outside in the evening or morning twilight hours and get a rare glimpse of one of three so-called naked-eye comets. These are comets that can be seen without a telescope or binoculars.
While comet buffs are excited at this opportunity, Fred Krupp, director of the Griffith Observatory in Los Angeles, California, cautions that the naked-eye cometsnamed Bradfield, NEAT, and LINEARwill appear faint and will be difficult for the inexperienced observer to see.
Comets are named after their discoverers. Comet Bradfield was found by amateur astronomer William Bradfield of Yankalilla, Australia, on March 23. It is his 18th comet discovery since he started looking in 1972.
NEAT and LINEAR are acronyms for automated Earth-threatening asteroid surveysthe Near-Earth Asteroid Tracking project (NEAT) and the Lincoln Near-Earth Asteroid Research project (LINEAR).
Speaking about LINEAR, Krupp said, "It may be that you can look up and see it without binoculars, but if you don't know the sky, you won't recognize it, whereas if you have binoculars you'll see the distinct shape of a comet."
For comet enthusiasts, the potential to glimpse three different naked-eye comets within a span of a few weeks is an anomaly. On average, a comet visible to the unaided eye appears about once every five years.
Brighter, more distinguishable comets like Hale-Bopp, which blazed across the night sky in 1997, appear about once a decade, according to Gary Kronk, a St. Louis, Missouri-based science writer who maintains the Comets & Meteor Showers Web site.
Kronk, who is keeping close tabs on these naked-eye comets, said "Bradfield will be fading and should be below naked-eye visibility by the end of April. LINEAR and NEAT are both brightening."
The comets are all near the sun, meaning the best time to view them will be in the twilight hours. Because of the lengthening days in the Northern Hemisphere, LINEAR, which appears in the morning sky, is a better target for observers in the Southern Hemisphere.
"The comet is a naked-eye object for observers in the Southern Hemisphere, and conditions steadily improve for them. Chances of Northern Hemisphere observers seeing the comet are nonexistent after the first full week of May," Kronk said.
Astronomers are uncertain as to how bright comet NEAT will become but say it will begin appearing above the southwestern horizon toward the end of evening twilight after May 4 and could remain visible to the naked eye through the end of May.
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