Photograph by Greg Hinson, My Shot
Published April 19, 2012
This weekend should offer the best view of the Lyrid meteor shower in years, with a dark moonless night during the peak of the annual sky show.
The Lyrids will put on their best showing overnight on Saturday and into the following morning, when the new moon will be essentially invisible from Earth.
Although the Lyrids usually put on a relatively modest display, astronomers say this April shower has been known to offer a surprise or two.
"Typical hourly rates for the Lyrids can run between 10 and 20 meteors. However, rates as high as a hundred meteors per hour are not uncommon," said Raminder Singh Samra, a resident astronomer at the H.R. MacMillan Space Centre in Vancouver, Canada.
"On rare occasions there may even be fireballs"—especially bright meteors—"streaking across the sky, too, making it quite a spectacular sight for observers."
Crossing the Stream
As with most other annual meteor showers, the Lyrids are thought to be caused by sand grain-size debris left over from a passing comet.
When a comet gets close to the sun, its ices vaporize, releasing dust grains and sometimes small lumps of rock that settle into orbit around the sun.
The Lyrids are thought to originate from comet Thatcher, whose 416-year orbit is nearly perpendicular to the plane of the solar system. That means the comet's debris trail doesn't experience many gravitational disturbances from planets, asteroids, and other comets.
Astronomers believe this stable stream of debris may be the reason the Lyrids have been a reliable sky show for centuries.
"Like clockwork every year in April, the Earth passes through the particle stream of this long-periodic comet, which last approached the sun in 1861," Samra said.
"These particles hit our atmosphere while traveling at high speeds and burn up, leaving behind streaks of light"—what we see as meteors.
Vega Guides the Way
The Lyrids' individual shooting stars will appear to radiate from the shower's namesake constellation, Lyra, near the bright star known as Vega.
Finding the Lyrids' so-called radiant is relatively easy compared with finding the apparent point of origin of other meteor showers, "since Vega can be spotted in even the heaviest of light-polluted cities," Samra said.
In Southern Hemisphere skies, the apparent point of origin will be at or below the horizon, so the Lyrids will seem to produce just a sprinkling of meteors.
But in the Northern Hemisphere, Vega will be shining nearly overhead by the time the shower reaches its peak in the predawn hours Sunday. Combined with a lack of glare from the moon, this alignment should offer ideal viewing conditions for the shower.
"Putting all of these factors together for viewers far away from city lights," Samra said, "this year's Lyrids may end up being better than years past."
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