The surprising Lyrid meteors

This week, Earth encounters the richest part of the Lyrid meteor stream, providing us with the opportunity to see a spritzing of 'shooting stars.' The best time to observe this shower is in the after-midnight hours, when the night side of Earth faces into its orbit, thus sweeping up more meteoritic debris. Avoid streetlights and brightly lit billboards, as their glare masks the fainter meteors. The Moon, too, can overwhelm the brief flash of a meteor, though if it displays no more than a crescent phase and is low in the sky, it should not pose too much of a problem.

Meteor showers are not really 'showers' at all, but an increase in the number of meteors seen per hour coming from a particular point in the sky, called the radiant. In the case of the Lyrid meteors, their paths, if traced backward on the sky, point in the general region of the constellation Lyra - hence the name 'Lyrids.' Meteors seen at this time coming from other directions are not associated with the Lyrids and are referred to as 'sporadics.'

Meteoroids - the stuff that actually causes the brief streaks of light in the sky during meteor showers - essentially consist of comet debris. When a comet ventures into the inner solar system, the Sun's warmth boils off the volatile ices and rocky particles that comprise the comet's crust, leaving a trail of comet crumbs. As Earth passes through the comet's detritus, some of the tiny bits of dirty ice burn up in the atmosphere, where they may be seen from the ground as shooting stars.

This week's meteor shower appears to radiate from a region of the sky between the constellations Lyra and Hercules. Lyra, a parallelogram of four stars with the brilliant blue-white star Vega near one corner, is overhead around 4 a.m. The radiant itself is located west-southwest of Lyra. In most years, observers can expect to see less than ten meteors per hour. Take note, however, that the rate can be significantly higher. A great display was seen in 1803 and once again in 1922. The shower pla-teaued in activity for the next 59 years, but picked up again in 1981. And in 1982, American observers reported between 75 and 90 meteors per hour around the peak. The shower's unpredictability makes the Lyrids an event not to miss.

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