This year, 2020, has been a bad year for many things. However, it should be a good year for the Geminid meteor shower. It usually is the best meteor show of the year, but this year it might be even better. It will peak tonight in the late hours of December 13 and early hours of December 14.
If you are familiar with meteor showers, you know that they are caused when the Earth, on its journey around the Sun, passes through the remnants of a comet. As comets travel through our solar system, the Sun’s heat vaporizes the outer layers of those rocky snowballs leaving debris in the comet’s path. When our planet crosses that path, tiny rock fragments enter our atmosphere and burn up as friction with the air superheats them. The annual December Geminid meteor shower is different and not caused by a comet.
One difference is that the Geminids are younger than other annual meteor showers, which people have observed for hundreds or thousands of years. People first observed the August Perseids in A.D. 36. The Lyrids, which occur in April, were recorded by the Chinese in 687 B.C. However, the Geminids were first seen in December 1862. Since then, they have returned every year, and they have gradually become more numerous as they reach more than 100 meteors per hour.
So if a passing comet does not cause the Geminids, what does? Astronomers solved that mystery in 1983 when the Infrared Astronomical Satellite discovered a small asteroid, which they named Phaethon. It travels in a very elliptical orbit around the Sun in a little less than a year-and-a-half. That orbit takes it closer to the Sun than Mercury and then beyond Mars to the asteroid belt. The asteroid becomes superheated in its close pass by the Sun. Phaethon also spins on its axis about every three-and-a-half hours meaning that the surface fries as it faces the Sun’s heat and then freezes in the cold of space. The freezing and thawing crack the surface, and the centrifugal force throws out fragments.
Most of the particles resulting from the rapid temperature change and spin are probably only about a millimeter in diameter. For that reason, astronomers believe that Phaethon was struck by another space object in the recent past, causing more meteoroids, which could explain the Geminid show’s quality. This year should be better than average, because the Moon will be new, meaning we will have a dark sky. Another thing that makes the Geminids the best meteor show of the year is that they came in at a much slower speed, so they move more slowly across the sky.
If you have clear skies and can find a dark place with an open view of the sky, you could be in for a treat. However, for those of us in the north, it will be cold. Wear warm clothes, lean back in a lounge chair, cover yourself with a blanket, and be patient. According to the Royal Astronomical Society of Canada, the peak should occur around 8 p.m.EST December 13 (0100 GMT December 14). However, there should be plenty to see for hours before and after that.
As you look at the night sky, remember that the shepherd boy David was looking at the same sky around three millennia ago when he wrote, “The heavens declare the Glory of God, and the sky above proclaims his handiwork (Psalms 19:1).” I am sure that David enjoyed an open dark sky with no light pollution from electric lights, but he also didn’t get to see the Geminids, the best meteor show of the year.
— Roland Earnst © 2020
