About the Perseid Meteor Shower

The Perseid meteor shower is a meteor shower which is active around August 12, 13 each year.

The Perseid meteor shower is a very easy meteor shower to observe.

One of the reasons is because every year it is almost guaranteed that many meteors will appear. It is known as one of “The 3 Major Meteor Showers,” along with the Quadrantids in January and the Geminids in December. If you observe from a location where the night sky is dark around the peak of the activity (note), during times when there are the most meteors, it is possible to observe over 40 per hour.

Also, because the active period of this meteor shower overlaps with the O-Bon holidays in Japan and summer vacation for many people, it is easy to stay up late and the meteor shower provides a reason to go someplace where the stars can be seen clearly. Furthermore, the active periods of the “Quadrantids” and the “Geminids“ fall in the cold winter season, but the active period of the Perseids falls in the lush summer time, so we don’t need to worry much about the cold during observations.

(note): The “peak” of meteor shower activity indicates the maximum activity of the meteoric swarm itself and the time when this maximum activity occurs, without consideration of the observing location or the moonlight conditions.

This Year’s Perseid Meteor Shower

This year (2016), we can observe the Perseid meteor shower under extremely good conditions.

One of the reasons why conditions are good is that because August 11 is the waxing quarter moon so that the Moon sets around midnight. After that, we can observe in a dark sky free from the effects of moonlight, and should be able to see even faint meteors. Another reason is that the peak is predicted to occur around 22:00 on August 12, Japan Standard Time, close to the time when it will be easy to observe meteors from Japan.

Also, it is expected that this year the meteoric activity will be more vigorous than most years.

For People Who Would Like to Know More

Please refer to “What is a Meteor Shower” for more information about what kind of phenomenon a meteor shower is, and to “The Perseid Meteor Shower” for a summary of the Perseids.

• What is a Meteor Shower? (Japanese only)
• “The Perseids Meteor Shower” (Japanese only)

To Observe the Perseid Meteor Shower

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

The Appropriate Time for Observations

The Appropriate Date for Observations

It’s predicted that the most meteors will be visible starting from midnight on August 12 until dawn on the 13th. It is also thought that many meteors will be visible before and after this, from midnight on the 11th to dawn on the 12th and from midnight on the 13th to dawn on the 14th.

The peak of the 2016 Perseid meteor shower is expected to occur at 22:00 on August 12, Japan Standard Time. At that time, there will still be an effect from moonlight, so the best time for observations is after the Moon sets around midnight. It is thought that meteors should continue to appear vigorously until dawn.

Furthermore, they’re not exactly at the peak, but from midnight on the 11th to dawn on the 12th and from midnight on the 13th until dawn of the 14th, we think that many meteors should appear, but not as many as on the peak night.

However, we don’t know when the weather will be clear, and this year in particular there is the possibility that meteoric activity will occur at times other than the predicted times. 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 Period when Many Meteors can be Seen

It is thought that more meteors than normal should be visible from about August 7 to August 15.

From about August 7 to August 15, the relatively active period of the Perseid meteor shower continues, so we think it should be possible to see more meteors than normal. However, as we move away from the day of the peak, the number of meteors which will appear decreases.

The total active period of the Perseid meteor shower is thought to last even longer, extending from around July 17 to August 24.

Time Period Suited for Observations

It would be best to observe between midnight and dawn as much as possible.

(For constant meteoric activity) the higher the elevation of the radiant point, the more meteors will appear. For the Perseid meteor shower, the meteor appearance conditions in each time period are as follows.

Before 21:00

Because the radiant point is still positioned low near the horizon, not many meteors will appear.

21:00 to Midnight

The elevation of the radiant point gradually rises and meteors begin to appear.

Midnight to Dawn

The elevation of the radiant point continues to increase, reaching its maximum before dawn. The number of meteors that appear increases along with the elevation of the radiant point.

But this year, it is necessary to consider the effects of moonlight, as explained in the following section.

The Effects of Moonlight

We Recommend as Much as Possible, Observing After the Moon Sets.
When observing at times when there’s moonlight, make sure that the Moon is not in your field of view.

This year the waxing quarter moon falls on the 11th and the full moon falls on the 18th. On the nights best suited to observations, the 11th to the 13th, around the time the sky gets dark after sunset, the Moon is in the sky; it sets around midnight. The Moon is bright after passing first quarter, so when the Moon is out, dim meteors drowned out in the moonlight can’t be seen. We recommend observing meteors after the Moon sets as much as possible. The moonlight goes away when the Moon sets around midnight.

If you observe when there is moonlight, it is best to observe in a direction where as little moonlight as possible enters your field of view and wait for meteors bright enough to standout in the moonlight.

You can look up the times when the Moon sets in the Koyomi Station of the Ephemeris Computation Office, NAOJ.
Ephemeris Computation Office

Directions Suited for Observation

If it is possible to watch a large area of the sky, it doesn’t matter what direction you look.

Meteors appear in all directions around the central point of the meteor shower. This central point is called the “radiant point.” For the Perseid meteor shower, the radiant point is near the γ (Gamma) star of the constellation Perseus. This is not to say that meteors appear only around the constellation Perseus where the radiant point is located. Meteors can appear anywhere in the 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.

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 we can see as wide an area of the sky as possible, where there are few streetlights, etc.

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 across 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 alone 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 is best to observe from locations as far away as possible from large cities.

How to Distinguish Shooting Stars Belonging to the Perseid Meteor Shower

Trace the meteor trail backwards and see if it passes through the radiant point in the constellation Perseus.

The following figure shows the night sky near the radiant point of the Perseid meteor shower around 0:00 midnight on mornings in August. Let’s look for the location of the radiant point by referring to this figure. It is a good idea to use familiar constellations, such as Cassiopeia, and bright stars, such as 1st magnitude Capella in the constellation Auriga, as guides. In a city, you probably can’t see stars as dim as some of the ones in this figure, but the faint stars are depicted to assist finding the radiant point. (In the actual sky, there is no mark to indicate the radiant point.)

The stars shift due to diurnal motion. Please be aware that a few hours before or after midnight the locations where the stars appear will differ from what is shown in this figure. (Within Japan there isn’t much difference due to observation location. Locations other than Tokyo can use this figure around midnight.) If you use a star finder, you can understand the starry sky at other times as well.

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, is it possible to see more than 45 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 to the naked eye.)

If you observe from inside 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.

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, your neck will get tired. It is best to prepare a reclining deck chair 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.

Video

Please take a look at this video of the Perseids taken on August 13, 2009.

The dots at the center of the image moving from upper right to lower left are meteors.

Reference Information

International Meteor Organization

This page summarizes meteor shower observation information and observational results.
Perseids 2015: visual data quicklook

Special Astronomical Phenomenon Pages • Campaign List (Japanese Only)

A list of past special astronomical phenomenon pages and campaigns conducted by NAOJ.

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