When we talk about meteor showers, the Perseids, observed in August, are usually the first to come to mind. But despite all their “promotion”, this is far from the most powerful meteor shower. In fact, this title is now held by the Geminids, which peak this week.
But why are the Geminids mentioned much less often than the Perseids? What is unique about this shower and what are the chances of seeing it this year? Let’s find out.
Comet in asteroid skin
Meteor showers occur when the Earth passes through a plume of dust left by a heavenly body. Usually it is a comet. However, in the case of the Geminids, things are much more interesting.
In 1983, the IRAS Infrared Observatory discovered an asteroid called Phaethon. It immediately attracted the attention of scientists for its unusual orbital characteristics. The fact is that Phaethon moves in a very elongated orbit, which is more like the orbit of a comet. In its movement, Phaethon crosses the orbits of all the planets of the Earth group. At its perihelion, it approaches the Sun at a distance of only 21 million kilometers. At this point, its surface is heated to a temperature of 750 °C. For comparison, Mercury never comes closer to the Sun than 46 million kilometers.
But that’s not all. Almost immediately after the discovery of Phaethon, astronomers suspected that it was somehow connected to the Geminids, as their orbital parameters are almost identical. It was suggested that the asteroid has a long dust tail, and when the Earth passes through it, a meteor shower is created.
In 2009, the STEREO Observatory confirmed this hypothesis by taking the first picture of Phaethon’s tail. Nine years later, the Parker Solar Probe obtained a more detailed image of its tail, which surprised scientists. The analysis showed that it contained much more material than Phaethon could have lost due to evaporation of matter during perihelion. Moreover, further observations showed that the tail probably consists not of dust but of sodium.
All of these oddities raised legitimate questions about the origin of Phaethon. According to one theory, it is a degenerate comet that has practically lost all its volatile substances. As for the tail, it was formed either as a result of a large collision or because Phaethon broke up several thousand years ago due to too much rotation.
Probably, some certainty in this matter will appear in 2030, when Phaethon will be visited by the Japanese DESTINY+ probe. The data it collects should help astronomers uncover the mystery of this mysterious object and establish whether it really was a comet in the past.
The most powerful meteor shower
Whatever the origin of the Phaethon, one thing is certain: the meteor shower it produces is currently the most powerful of all that can be seen in the Earth’s sky. The ZHR (Zenith Hourly Rate) for the Geminids is 150. This number determines how many meteors per hour an observer would be able to see in an “ideal” sky if the radiant were at its zenith. For comparison, the ZHR of the Perseid shower is currently only 100.
Many people have probably already asked themselves a natural question: if the Geminids are so powerful, why is there so little talk about them? The answer is quite simple – just look at the calendar and then at the sky. To put it mildly, December weather in the temperate latitudes of the northern hemisphere is not particularly conducive to astronomy. The sky is often overcast with dense clouds. And clearings occur during frosts, which also do not motivate you to go out of town to see a starfall.
The Perseids are observed in August, when there are many clear and still warm nights. It is not surprising that they are much more popular than the Geminids.
Where and when to observe the Geminids
The Geminids are observed between December 2 and 21. This year, the peak of their activity will be on the night of December 13-14. The radiant of the stream (the point of departure of the meteors) is located in the constellation Gemini.
It’s worth noting that the Geminids are one of the few large meteor showers that can be observed before midnight. By 22:00, the constellation Geminids will be high enough above the eastern part of the horizon. But you don’t have to look directly at the constellation. In fact, meteors will appear all over the sky. The Geminids are distinguished by their brightness, intense color, and relatively low speed.
Unfortunately, in addition to the capricious winter weather, there is another circumstance that will make observing the Geminids this year much more difficult – the Moon. During the Geminid peak, its disk will be 97% illuminated and it will create a very strong illumination of the sky, which will make it extremely difficult to see a significant number of meteors even in perfect weather. In order to see as many meteors as possible, we recommend hiding in the shadow of the Moon – standing so that an object (for example, a tree or a house) blocks it.
However, the fact that it is almost impossible to see the Geminids this year does not mean that it will always be like this. In the following years, the conditions for observing the stream will be much better. During the peak in 2025, the lunar disk will be illuminated by only a third, and in 2026 – by 15%. So observers who are lucky with the weather will be able to see a full-fledged celestial show.
