The Geminid meteor shower will reach its peak this evening

Dwarfing August’s famous Perseid meteor shower, December’s Geminids are arguably the best meteor shower of the year, with shooting star rates theoretically up to 75-125 per hour in perfectly clear, dark skies and away from any light pollution. More realistically, however, you will see between 30 and 40 meteors per hour (which is still very good), as many are too faint to see with the naked eye and few of us have the perfect spot with a clear viewing location can find skies free of urban light pollution. However, this year we are at a disadvantage because the moon is almost full, reducing the number of possible shooting stars to just 10-20 per hour, possibly even fewer due to patchy cloud cover. But still, it’s always worth a try as you might get lucky and catch a quick shot or even a fireball.

Peak usage will be on Friday evening, December 13th, into the early hours of Saturday the 14th, with significant numbers of meteors likely still visible on the evening of December 14th. And unlike other meteor showers, which are usually best seen in the few hours before sunrise, the Geminids can often see a few bright streaks flying by early in the evening when the sky is clear, with the show only increasing in intensity at night increases.

December’s cold, dry air, free of the haze that often obscures meteors in the warmer months, is one of the reasons, along with the typically high shooting star rates, that this is a great meteor shower to watch. You just have to look it up. It doesn’t matter which way you look, as long as you look up. And to see as many shooting stars as possible, you should try to find a place where you have the widest possible view of the sky and is as far away from light pollution as possible. And although meteor rates will be much lower, the Geminids will remain active until the 17th.

WHY THE SHOW

The Geminid meteor shower occurs when Earth passes through the cloud of dust left behind each time the 3.6-mile-wide asteroid, known as 3200 Phaethon, orbits the sun every 1.4 years. Each time 3200 Phaethon comes closest to the Sun on its journey through the solar system, its surface heats up to a temperature of about 700 degrees Celsius, causing it to shed particles that form the dust cloud.

Interestingly, most meteor showers are caused by particles thrown off by comets. However, this meteor shower and January’s Quadrantids are the only two major meteor showers that originate from anything other than a comet.

The particles that make up the dust cloud are tiny, generally the size of grains of sand or pieces of cereal, and hit the atmosphere at 50 to 75 miles altitude at a speed of about 18 to 22 miles per second, or about 78,000 miles per hour (which is actually considered slow). Due to the relatively low speed of the particles, the Geminid’s light streak is easy to see. This streak of light is caused by the enormous friction between the meteor and the upper atmosphere, which rapidly heats the air molecules in its path to thousands of degrees Fahrenheit, creating a cushion of superheated air that runs ahead of the particle. When these superheated molecules cool, which happens almost instantaneously, they emit light, which creates the streak we see. The faster the particle moves, the greater the friction and the hotter the air and the brighter the meteor streak.

The reason that these and other meteor showers are better in the hours just before sunrise than in the early evening, according to Sky & Telescope, is that the Earth’s orbital speed combines with the speed of shooting stars in the hours before sunrise, resulting in the arrival speed increased, which in turn leads to brighter stripes. However, in the evening, the relative speed of the particle impact is slower, so the meteor streaks are fainter and, in most cases, less visible.