STARRY NIGHTS
by Gary Boyle
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April 19, 2003
APRIL SHOWERS
Our solar system consists of the sun and its nine siblings – the planets. Between the orbits of Mars and Jupiter lies the asteroid belt. This 200 million kilometer wide path of rubble is where a planet should be. However tidal forces simply did not allow this body to form. Some asteroids do pay a visit to our neighborhood as they sails past our earth. Measuring a few kilometers in diameter a collision with us would not be a good thing. Such a mighty collision killed the dinosaur and 90% of biological life around 65 million years ago.
Long after the sun and planets formed some 4.5 billion years ago microscopic dust, sand size grains and larger pieces float helplessly in space. Venturing too close, they fall prey to a planet’s or moon’s gravity. Striking a planet’s atmosphere at tens of kilometers per second, the still of the night is interrupted by a streak of light. Commonly referred as shooting or falling stars, a few meteors can be seen on any given clear night.
There are however, times throughout the year that earthlings can see a great number of bright meteors over a very short time period. Meteor showers can produce tens to hundreds of (shooting stars) per hour. These special displays originate from dusty comets. As flying mountains of ice approach the sun, solar winds literally blow fine particles off the comet’s body thus forming a long dust tail a few million kilometers in length. If by coincidence our planet encounters this dusty path on our yearly orbit around our closest star, we are honored by a meteor shower the same date each year.
A spring time meteor shower called the Lyrids will occur between April 22nd and 23rd. The peak of this weak shower will take place between midnight and 3:00 a.m. on the morning of Wednesday the 23rd. Rates should reach around 18 meteors per hour with a possible outburst of 90 per hour for a short duration. Such outbursts have been witnessed in 1803, 1922, 1945 and most recently in 1982. A 60% lit moon will rise in the southeast at 3:06am EDT thus washing out faint meteors. Look for a red object four lunar diameters above the moon. This is the planet Mars.
The parent comet responsible for producing this dusty path is Comet Thatcher. Discovered by A.E. Thatcher of New York on the night of April 5th, 1861, it returns every 415 years. As it revisits our neck of the woods its tail deposits new material along the same path.
Do not be afraid as grit the size of the period at the end of this sentence burn up high above you. Some showers such as the Leonids in November produce peas size projectiles. These fireballs are so bright they easily light up the ground like a flash photo. During its high speed descent of 49 km/sec, electrons from the particles are stripped off the object. As these atoms recapture its lost electrons, light is emitted. An average meteor’s tube of light around the tiny body is about five meters wide. Occurring 100 kilometers above the earth, the light path resembles that of a human hair. The flash lasts less than a second.
Although the radiant (area where the meteors appear to come from) is in the constellation Lyra sparks can be seen anywhere throughout the sky. The name Lyrids mean the kids of Lyra. This constellation rises around 10:00 p.m. but allowing the sky to shift a couple of hours will result in the radiant rising higher with more meteors seen. To enjoy this display, simply dress warm, pack a lawn chair and head out of town. Escaping the umbrella of light pollution allows you to enjoy a dark sky and catching a glimpse of faint meteors. Do not worry about bringing binoculars or a telescope. Just use your eyes.
One of the best meteor showers of the year is the Perseids in August. Here the nights are warm with about 120 meteors blazing in all directions per hour. But do not bypass the Lyanids if the night is clear. Although the numbers are low, a cloudy night could ruin the August display.
Who knows you might be treated to an outburst you might never forget.
