The Geminid meteor shower is a meteor shower which is active around December 14 each year.

One characteristic is that many meteors are almost guaranteed to appear every year. It is known as one of “The 3 Major Meteor Showers,” along with the Quadrantids in January and the Perseids in August because many meteors appear every year. When you observe around the peak time under a dark night sky, you might observe over 40 per hour at most.

Another characteristic of the Geminids is that they appear before midnight and are visible throughout the night. Among the 3 Major Meteor Showers, the Perseids and the Quadrantids appear mainly from midnight to dawn. However, the Geminids mainly appears from an early time around 20:00. This meteor shower is easy to observe for many people, especially children.

Therefore, the Geminids is ideal for people who want to observe their first meteor shower.

Here we have collected information which could be useful for observing this year’s Geminid meteor shower.

The Appropriate Time for Observations

The Appropriate Date for Observations

It’s predicted that the most meteors will be visible starting from the night of December 13 until dawn on December 14.
It is also thought that a certain amount of meteors will be visible on the nights of the 12th and the 14th.

The peak of the Geminids is predicted to occur around 16:00 on December 14, Japan Standard Time. But, this time is during the daytime, so you cannot observe meteors in Japan. It is expected that the largest number of meteors can be seen a few hours before and after 0:00 on the 14th (after midnight on the 13th), which is the last night before the peak.
Furthermore, you can enjoy some meteors on the nights of the 12th and the 14th.

However, we don’t know when the weather will be clear. It is also possible for meteoric activity to occur at times other than the predicted time. Regardless of the above predictions, please observe for as long as possible, as many nights as possible. This is the only way to improve your chances of seeing meteors.

The total active period of the Geminids is thought to last even longer, extending from around December 4 to December 17. However, as we move away from the day of the peak, the number of meteors which will appear decreases.

Time Period Suited for Observations

It would be best to observe between 22:00 and dawn as much as possible.

When the meteoric activity is constant, the higher the elevation of the radiant point, the more meteors will appear.

For the Geminids, meteors will appear from around 20:00. Continue observing for a while and you can see some meteors. However, since the radiation point is still not so high around this time, it is not the full shower. From about 22:00, meteors begin to appear, and it is thought that the meteor shower will be visible until the morning.
The radiant point reaches its highest elevation around 2:00.

The Effects of the Moonlight

There are almost no effects from the Moon.

This year, December 10 is the last quarter Moon and the 18th is the new moon. So, there are times when the Moon shines around the peak period. However, the Moon is not very bright because it is thin. Also, it appears around the dawn, so there will be little influence when observing meteors.

You can look up the times when the Moon rises and sets in the “Koyomi Station” of the NAOJ Ephemeris Computation Office.

Number of Meteors Which Can Be Seen

If you observe from a location with a sufficiently dark sky at the time with the most meteors, it should be possible to see around 40 per hour.

Here we assume that you are observing from a location with a sufficiently dark sky (i.e. 5.5 magnitude stars are visible with the naked eye when there is no moonlight.)
If you observe under town lights or at times other than the peak, the number of meteors which can be seen will be reduced to a fraction of this amount. On the other hand, people with sharp eyesight or veteran meteor observers might be able to catch twice as many.

Directions Suited for Observation and How to Distinguish Meteors Belonging to the Geminids

It doesn’t matter which direction you look. Please watch a large area of the sky.

Meteors appear to radiate around the central point of the meteor shower. This central point is called the “radiant point.”
For the Geminid meteor shower, the radiant point is near the star Castor, which is one of the two bright stars in the constellation Gemini.

This is not to say that meteors appear only around the constellation Gemini where the radiant point is located. Meteors can appear anywhere in the night sky. For example, even if you look in the opposite direction from the radiant point, on average you can see as many meteors as if you watched in the direction of the radiant point.
So, you should concentrate on a wide area of the sky without worrying about the radiant point. The wider the area of sky you watch, the more likely you are to see many meteors.

During the period when the Gemini meteor shower is active, meteors other than the Geminids might also appear.
To determine whether it is one of the Geminids or not, please follow the meteor trail backwards and see if it passes through the radiant point of the Geminids. If it doesn’t point back towards the radiant point, it isn’t one of the Geminids; if it does, it is highly probable that it is one of the Geminids.

The length of the meteor trails changes based on their relative position to the radiant point. Because meteors which appear near the radiant point are flying towards us, most of them have short trails. In contrast, in directions removed from the radiant point, we see meteor trails from the side, so most of them appear long.

Locations Suited for Observations

Let’s observe from locations where you can see as wide an area of the sky as possible, where there are few streetlights.

In locations where it’s not possible to see much of the sky, such as in the woods, or a veranda where only a portion of the sky is visible, you won’t be able to catch meteors appearing over the entire sky. Please search for a site where you can see as wide an area of the sky as possible, with few objects blocking your view.

Also, you should choose a location with few streetlights or other artificial lights. The light from meteors is very dim compared to the brightness of streetlights, etc. If there is much artificial illumination, you won’t be able to see faint meteors overpowered by that brightness. This will reduce the number of meteors you can see.

In a large city or the surrounding area, the light from the entire city interferes with viewing the meteors, making it impossible to see faint ones. It's better to observe from locations as far away as possible from large cities.

Points for Observations

• Specialized equipment, like telescopes or binoculars, is not required. You should observe with the unaided eye. When using a telescope or binoculars, your field of view narrows drastically, so this equipment is not suited for meteor observations.
• If you observe for long periods while standing, you will get tired. It is best to prepare a picnic sheet so that you can observe while lying down.
• After going outside, your eyes need to adjust to the darkness, so please observe for at least 15 minutes.
• As with any outdoors activity late at night, please be careful to avoid accidents.
• Please use good manners: do not use loud voices near people’s homes, do not enter off-limits areas, etc.

This video, taken in the middle of the night of December 14, 2014, captured 7 of the Geminids meteors in the span of about 3 minutes, including one of startling brightness.

Meteor Shower Explanation Movie

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