(Machine translation by DeepL + adjustments by Gyegyopon, Translated article written for Japan without major changes, Sorry some Japanese language is still there)
Hello, this is Gyegyopon.
The Perseid meteor shower, which is active in mid-August, is one of the “three major meteor showers” and you can see a lot of meteors every year without missing.
If you go to a place with a good view of stars, you can see a lot of meteors, and you may be able to see meteors even in the bright sky of a city.
This article summarizes the status of the Perseid meteor shower in 2024 and information about meteors.
I hope this article will be helpful for those who want to see meteors and learn more about meteors.
Main text
If you want to know the condition of the Perseid meteor shower this year quickly, please read “Summary“.
“What is the Perseid Meteor Shower?” and after that, the contents of ‘Summary’ are explained in a little more detail.
If you want to know more about meteors, please continue reading “What are meteors?“
Summary
The Perseid meteor shower in 2024 is best viewed on one of the three nights1 from the night of August 11 to the morning of August 14, with the greatest number of meteors expected to be visible before dawn on August 13. If you are in a dark sky, you can expect to see about 30 meteors per hour when the most meteors are visible.
On any given night, a modest number of meteors will begin to appear around 21:00, and the number of meteors will increase as dawn approaches after midnight.
Don’t worry about which direction in the sky to look. Meteors can appear in many different directions.
The best place to view meteors is where the sky is dark and you have a wide view of the sky. It is best to stay as far away from large towns as possible.
What is the Perseid meteor shower?
The Perseid meteor shower is a meteor shower that is active in mid-August every year. The Perseid meteor shower is one of the three major meteor showers, which are the three meteor showers where you can see a lot of meteors. The other two meteor showers are the Quadrantids in January and the Geminids in December.
The Perseids are “easy to see” because many meteors appear consistently every year2, they are visible during the warmer months, and many people are on summer vacation. However, the fact that most of the meteors are visible from after midnight to before dawn may pose a bit of a hurdle.
Perseid meteor shower this year
The Perseid meteor shower in 2024 is expected to reach its maximum3 around 23:00 on August 12. Since the Perseid meteor shower is best viewed in the pre-dawn hours, the best time to see a large number of meteors in Japan is after the maximum on August 13, before dawn. We expect to see about 30 meteors per hour in dark sky.
One night earlier, before dawn on the 12th, and one night later, before dawn on the 14th, you can expect to see 15 to 20 meteors per hour.
Regarding the temporal variation in the number of meteors, (this does not depend on the year) meteors of the Perseid meteor shower tend to start appearing there around 21:00 and increase in number after midnight and toward dawn. (This may be a little hard for those who are not good night owls.) However, it is not impossible for meteors to appear before 21:00, so don’t give up and try to observe them even in the early hours of the night.
Around the time of this year’s maximum, the Moon before the waxing moon will set before midnight; on August 12, the Moon will set around 22:004. Moonlight makes it difficult to see dark meteors. This year, however, the moon will set before midnight, so after that we will be able to see meteors in the dark sky without the influence of the moon.
Direction in which meteors are visible
Meteors appear in various directions in the sky. Although it is called the “Perseid meteor shower,” meteors do not appear only in the direction of the constellation Perseus.
Meteors in meteor showers have a distinctive appearance.
They radiate outward from a point in the night sky called the “radiant point”. It is called the “Perseid” meteor shower because the radiant point is located near the constellation Perseus.
Meteors that appear near the radiant point are moving toward us, so their paths are short and they move slowly. On the other hand, meteors that appear some distance away from the radiant point have longer and faster paths because they are moving sideways.
If you find a meteor in the night sky and it is moving in a direction straight away from the Perseid meteor shower radiant point, it is very likely to be a Perseid meteor shower meteor5. On the other hand, meteors moving in other directions are not Perseid meteor showers6, even during the active period of the Perseid meteor shower.
How to observe meteors
To see many meteors, try to view them in a place where the sky is as dark as possible (usually, you can see many stars). If the sky is bright, dark meteors will be obscured by the brightness of the sky, and the number of meteors you can see will be reduced.
As for where the “dark sky” place is, roughly speaking, the further you are from a large city, the darker the sky will be. The sky becomes brighter in a large town, because there is a lot of artificial light there, which illuminates the sky and makes it brighter.
Even when observing in the vicinity, it is best to find a place with as few lights as possible nearby.
It is also important to have a wide view of the sky. Meteors appear in various directions in the sky, so if you have a wide view of the sky, the probability of meteors appearing there will increase.
No special tools are needed to observe meteors. Observe with the naked eye.
If you use binoculars or a telescope, your field of view (range of vision) will be very narrow, which is not good for capturing meteors that may appear anywhere.
It takes time for your eyes to adjust to the dark. It is best to let your eyes adjust for about 15 minutes after going to a dark place. During this time, do not look at anything bright, such as a smartphone screen.
It is very tiring to stand and watch the sky for a long time.
You can easily observe the sky by lying down on a leisure sheet or something similar. (Try your best to sleep during the day so you don’t fall asleep.)
Don’t forget to deal with mosquitoes and other insects7. You cannot concentrate on watching meteors if you are worried about insects.
Shouting at night or entering places you are not allowed can cause trouble. Please follow the rules and behave with good manners. Also, since you will be working in the dark, be careful of accidents.
What are meteors?
Here are a few more details about meteors.
A meteor is a phenomenon in which dust particles, like grains of sand flying through space, fly into the Earth’s atmosphere at high speed and shine.
All meteors in a single meteor shower are born from dust grains originally ejected from a single comet8. In the case of the Perseid meteor shower, the comet that ejected the dust grains is Comet Swift-Tuttle (109P/Swift-Tuttle). The dust grains ejected from the comet are spread throughout the comet’s orbit, and when the Earth passes through the orbit every year, the dust grains plunge into the Earth’s atmosphere9. The dust grains collide violently with the Earth’s atmosphere, glowing and becoming meteors.
Since all dust grains fly into the sky from the same direction to the observer, meteors appear to radiate from a certain point. The central point from which meteors appear radially is called the “radiant point”. The radiant point is conceptual (thought up in the mind), so if you look closely at the night sky, you will not see anything there.
If a meteor happens to appear at the radiant point, it appears as if light appears and disappears without moving. Such a meteor is called a “stationary meteor”10. From another point of view, a stationary meteor is a meteor that comes straight toward you.
Number of visible meteors
The number of visible meteors is related to the altitude of the radiant point and the brightness of the sky at the location of observation, in addition to the activity of the meteor shower itself.
Activity of the meteor shower itself
The dust grains spread over the comet’s orbit have thick (dense) and thin (sparse) portions. If the earth plunges into the dense part, many dust grains will fly into the atmosphere and many meteors will appear.
The increase in the number of dust particles entering the atmosphere and the increase in the number of meteors are called “meteor shower is active”.
Roughly speaking, dust grains encircle the comet’s orbit in a cylindrical shape, with the dust grains becoming denser toward the center. Therefore, when the earth approaches the center of the dust grains, the meteor shower becomes more active, reaching a maximum at the densest part, and after the maximum, the dust grains gradually become sparser and the activity of the meteor shower calms down.
Altitude of radiant point
If the activity of meteor showers is the same, the higher the altitude of the radiant point, the more meteors will appear.
Meteors of the Perseids tend to appear around 21:00 and increase in number from after midnight to dawn, because the altitude of the radiant point gradually increases.
The main reason why the number of meteors increases as the altitude of the radiant point increases is due to the difference in the area over which the dust grains fly into.
Let us compare the case where the same number of dust grains come from directly above the head and the case where they come from an angle. When the dust particles come at an angle, the same number of dust particles are spread over a larger area. Therefore, fewer meteors will be visible11.
Meteors do not appear when the radiant point is below the horizon12.
Sky brightness
The more dark the sky (where even the faintest stars are visible) is, the more meteors are visible. Conversely, in a bright sky (where dark stars are not visible), the number of visible meteors will be smaller because dark meteors will not be visible.
Besides differences in the brightness of the sky depending on location, the moon also affects the brightness of the sky.
When the moon is very thin, it has little effect, but the thicker the moon is, the brighter it becomes. It is brightest at the time of the full moon, and the sky lit by the full moon is so bright that only fairly bright meteors can be seen.
In the case of the Perseid meteor shower, the number of visible meteors more than doubles when observed in a sky where stars up to one magnitude fainter are visible13.
Some activities that are out of the ordinary
The Perseid meteor shower reaches its normal annual maximum around 140.0 degrees solar ecliptic longitude14. Based on this, the 2024 maximum is predicted to be around 23:00 on August 13.
On the other hand, in addition to the normal activity of meteor showers, there is sometimes a secondary activity that is expected to be different from the annual trend. Calculations can predict in advance that the earth will plunge into the dense areas of dust grains (called “dust trails,” “filaments,” or simply “trails”) that have been ejected from comets in the past.
Furthermore, unexpected appearances (“sudden appearances”) can be captured by observation without prior forecast.
Secondary activity in 2024
Several secondary activities are expected in 2024.
One is the activity on August 12 around 18:00. It is expected that the earth will cross the sparse trail around this time. However, the radiant point is quite low in Japan at this time, so even if meteors appear more than usual, it will be difficult to catch them in Japan.
A researcher believes that five old trails and the Earth’s orbit will intersect between about 13:00 and 20:00 on August 12. Four of the trails were ejected from comets more than 1,300 years ago.
In 2021, sudden appearance a day and a half after the normal maximum
The normal maximum for the Perseid meteor shower in 2021 was around 4:00 on August 13. As expected, many meteors appeared around that time. However, one and a half days later, at around 17:15 on August 1415, the activity more than twice that of the normal maximum was observed.
A similar, even though weaker, phenomenon seems to have been captured on the radio observation in 2022.
Let’s actually observe
Predicting the date and time of meteor maxima and the number of meteors is not a sure thing. You will not know when and how many meteors you will see until you actually see them. Even if the date and time are outside the predicted time of maximum or activity, you may be able to catch an unexpected appearance when you actually observe it.
Related Information
reference
- National Astronomical Observatory of Japan
- Perseid meteor shower at its maximum (August 2024) (General)
- Koyomi Station (Time of moonset in various locations)
- SATO Mikiya: Information on the Perseid meteor shower in 2023 (General)
- International Project for Meteor Radio Observation
- Meteor showers in August (Radio wave observation) (General)
- Meteor showers in August (General)
- IMO (International Meteor Organization): 2024 Meteor Calendar [in English] (expected appearance, population index, secondary activities)
*On page 12, you will find an explanation of the Perseid meteor shower. - UCHIYAMA Shigeo: Aggregate calculation method for visual observation of meteors (difference in the number of meteors depending on the altitude of the radiant point)
Others
脚注
- Or all three nights, of course.
- The Geminid meteor shower is also stable. The Quadrantid meteor shower can be hit or miss depending on the year.
- It says the meteor showers are most active or the time when the meteor shower is most active.
- The time of moonset varies from place to place. This article describes the time in Tokyo, but the times are not significantly different in other areas. For example, on August 12, moonset is at 22:13 in Tokyo, 21:46 in Sapporo, 22:33 in Osaka, and 22:57 in Fukuoka.
- It is possible that meteors that do not happen to be in the Perseid meteor shower will move in a similar direction, so this is not a 100% reliable method of identifying meteors. In order to identify meteors with certainty, you observe meteors from two or more points and use the principle of triangulation to determine the three-dimensional path and velocity of the meteors. If the original dust grain has the same orbit as the parent comet, then it can be judged to be a meteor from that meteor shower.
- Meteors that do not belong to a specific meteor shower are called “sporadic” meteors.
- Gyegyopon often uses mosquito coils because I don’t like insect repellents applied to my skin. (This is not a recommendation. Use your own judgment in each situation.) If you place mosquito coils in four places around you, they will protect you from insects no matter which way the wind blows. Please be careful with fire.
- It is called “Parent comet.”
- Therefore, the meteors in a given meteor shower appear at the same time each year. Also, only comets whose orbits intersect with the Earth’s orbit can be the parent comet of a meteor shower.
- You may want to know the probability of seeing a stationary meteor. However, there is no clear definition of a stationary meteor, so the probability depends on how much movement you consider acceptable. If you are willing to call it a stationary meteor even if it moves a little, the probability will be high, and if you think it moves at all, the probability will be close to zero.
- If the altitude of the radiant point is θ degrees, the area into which the same number of dust particles fly is (1/sin θ) times larger than when the radiant point is at zenith (directly above the head).
This means, for example, that if the altitude of the radiant point is 30 degrees, the area of the atmosphere over which the same number of dust particles can fly into is twice as large (1/sin 30° = 1/0.5 = 2), thus halving the number of meteors. (The figure on the right shows the radiant point altitude as 30°.) - The radiant point is below the horizon, which means that dust grains are flying in from behind the earth. In that situation, no meteors will appear because the earth is in the way and the dust particles will not fly into the atmosphere above you. However, when the radiant point is “just below the horizon,” meteors may appear, although they are very few in number.
- “Population index” is a numerical expression of how many times more meteors are visible when stars up to one magnitude fainter are visible. For example, suppose you observe a meteor shower with a population index of 2, and you see 10 meteors in the sky where you can see stars up to 3rd magnitude (the faintest stars). If you observe a meteor shower in the sky where you can see stars up to 4th magnitude, you would expect to see 10 x 2 = 20 meteors. And 10 x 2 x 2 x 2 = 80 meteors in a sky where you can see stars up to 6th magnitude.
The population index of the Perseid meteor shower is 2.2. - Although the name “solar ecliptic longitude” is “solar…,” it is best to think as indicating the position of the earth as it orbits the sun. It is an angular measure of how much the earth has moved from a specific location, the vernal equinox, around the sun by its orbit.
- Around 141.48 degrees of solar ecliptic longitude.
