Meteor Showers

The peak of the 1998 Leonid meteor shower (rich in bright fireballs), shown in a four-hour time exposure through a fisheye lens, and taken by Juraj Toth of Modra Observatory. This photograph demonstrates how the meteors in a particular shower appear to emanate from a certain point in the sky called the radiant. On a given night, this radiant point will remain relatively stationary with respect to the background star constellations; but will rise, traverse the sky, and set in the same manner as the sun and moon.

• Viewing Activity from the 2010 Perseid Meteor Shower
• Meteor Shower Basics
• Major Showers Through the Year
• 2010 Meteor Shower Calendar
• Explanation of the 2010 Meteor Shower Calendar
• Additional On-Line Resources

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Viewing Activity from the 2010 Perseid Meteor Shower

This chart represents plotted Perseid meteors (arrows) as seen from mid-northern latitudes while facing north near 4:00 a.m. local daylight time on August 13. This chart was created using SkyChart III Version 3.5.1 from Carina Software.

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In mid-July the Earth begins to encounter debris released from long period comet 109P Swift-Tuttle. The particles encountered at this time travel in a path far from the mainstream orbit of debris from the comet. Their radiant (the area of the sky these meteors seem to come from) lies on the Andromeda/Cassiopeia border and only their swift velocity reveals their identity as early arrivals of the Perseid meteor shower. The moon is favorable for observing these early Perseids up to July 23, when the waxing gibbous moon will remain in the sky most of the night, obscuring all but the brightest meteors. From then until August 3rd, the moon will interfere with observing during the prime morning hours. During the first week of August the Perseids will share the spotlight with the Delta Aquariids (SDA). Both showers will be equally strong producing 5-10 shower members per hour, depending on your latitude. During the morning hours the SDA radiant will be located low in the south while the Perseid radiant will lie in the opposite direction. It will be somewhat of a battle between the two showers with them shooting meteors at each other. As the second week of August arrives activity from the Delta Aquariids will wane while the Perseids will surge in activity.

The moon becomes a non-factor by August 7th. Also by now the Perseid meteors now become more noticeable as their rates are approaching that produced by the random (sporadic) activity seen each hour. The radiant has traversed the southern portions of the constellation of Cassiopeia and now lies among the stars of Perseus. At this time of year, the constellation of Perseus (the hero and slayer of the dreaded Medusa) lies on or near the northern horizon at dusk. This is the absolute worse time to try to view Perseid activity as a great majority of the meteors occur below the horizon or are blocked by trees and hills. The occasional Perseid that does manage to shoot upward at this time of night is often a magnificent sight as it only skims the upper portions of the Earth's atmosphere. This allows it to last several seconds instead of the normal sub-second streak. The Perseids seen at this time of night will also travel in long paths adding to the impressive scene.

As the evening progresses, the stars of Perseus begin to climb higher into the northeastern sky. Just how high depends on your latitude. The further north one lives, the further the radiant will lie above the horizon. If you are located too far north though, the sun sets later and rises earlier limiting the time you have to view the activity. For those located south of the equator, the Perseids are strictly a post midnight affair, as the radiant does not clear the horizon until the morning hours. For those located south of 35 degrees south latitude, the Perseids are not visible at all as the radiant never clears the northern horizon. So those situated near 30 degrees north latitude probably enjoy the best combination of high radiant altitude and long nights in which to enjoy the display.

As the midnight hour passes the Perseid activity begins to kick into high gear. The radiant now lies high enough above the horizon from most locations to allow meteors to be seen shooting in all directions, including straight down. To see the most activity it would be advisable to view approximately half up in the sky with the radiant toward the edge your field. Personally, I like to view above the radiant at this time and then have it move through my field of view as the night progresses. This basically means that I face northeast at an altitude of 45 degrees the entire night. I was never one that wished to get out of a warm sleeping bag to move my chair in the middle of the session!

The best Perseid activity, no matter the date or location, is usually seen during the last hour before the start of morning twilight, when Perseus lies highest above the horizon in a dark sky. This is usually between the hours of 0400 and 0500 local daylight time for most of us. While gazing high into the sky, one must be comfortable in order to avoid neck strains and fatigue. A folding lounge chair is the perfect solution. It is easily portable and comfortable. Be sure to also have a blanket or sleeping bag too, even if temperatures seem balmy. It's surprising how the inactive body can become chilled even though the air temperatures seem warm.

The Earth is predicted to pass closest to the core of P109 Swift-Tuttle near 0100 Universal Time on August 13. This timing favors western Asia. Both the mornings of August 12 and 13 will be good for North America, with perhaps the 13th offering slightly more activity due to the fact we are closer to the predicted time of maximum activity.

On the mornings of August 12 and 13, I would estimate peak rates to be near 60 for those under transparent rural skies. Those under dark but hazy skies should still be able to see 30-40 Perseids per hour. Those under urban skies will be lucky to exceed 20 per hour.

Transparency is an important factor as many of the Perseid meteors are faint. A hazy, humid night can hide these faint meteors making the display seem much weaker than it actually is. This haze also scatters light from ground fixtures, making it difficult to view the display from urban areas. It is difficult for those in the eastern half of North America to escape this haze. Their only recourse is to find a safe rural site away from urban lighting. This will help with the problem of scattered surface light but not the dimming of the stars above. Observers in the west often have the ability to travel to mountain sites above the haze where one can see the stars and meteors right down to the horizon.

The characteristic Perseid is a bright white or yellow meteor lasting less than a half second. The brighter meteors usually leave a persistent train or "smoke trail" that lasts a second or two after the meteor has vanished. This is not really smoke at all but rather ionized gas created by the meteor passing through the atmosphere at tremendous velocities.

One of the best times to try and photograph meteors is during the Perseid meteor shower. All you need is a camera capable of exposures lasting one minute or longer. Simply aim the camera high enough to clear the horizon and set the focus to infinity. Don't aim the camera straight up as this is the worst direction for meteor activity. The layer of air directly above you is the thinnest therefore less activity will be seen there compared to the denser portions of the atmosphere located closer to the horizon. Also try to center the camera 30-60 degrees from the radiant so that the meteors are long enough to be easily seen on your photograph. Meteors appearing near the radiant will appear shorter as they are traveling in a direction toward you. It is also advisable to use the fastest film/ ISO setting possible to increase the sensitivity of you camera. Meteors will appear as straight streaks overlapping the curved trails created by the stars moving through the field of view. The length of the star trails will depend on the length of your exposure and the direction you point the camera. Pointing your camera northward will decrease the length of the star trails. Some photographers eliminate the stars trailing by mounting their cameras on motor driven mounts. With this setup the stars remain as pinpoints while meteors are obvious streaks.

It is also enjoyable and scientifically useful to record the meteor activity you see. Experts in meteor astronomy can reduce your data and compare it to others all over the world if you use certain standards in your reporting. First and foremost is to provide the accurate time of your observing session. It is helpful to time each meteor but not absolutely necessary as long as the start and finish times are provided. The observing conditions are very important to properly record, especially if your field of view is obscured by clouds or trees. These obscurations should be recorded to the nearest ten percent. Once per session is fine for trees but at least every 15 minutes for changing conditions such as cloudiness. The limiting magnitude of the sky in your field of view should also be recorded at least once an hour. The easiest way to do this is to count the number of stars visible in pre-selected areas of the sky. These areas and the resulting limiting magnitudes are available from the IMO web site at: http://www.imo.net/visual/major01.html#table2

It is also necessary to classify each meteor seen. On August 13, a majority of the meteors seen will be Perseids. There is no way that every meteor is a Perseid that night. There are on average 5-10 random meteors occurring each hour. These can come from any direction and be of any velocity, usually slower than the Perseids. Perseids will always line up with the radiant in Perseus and will usually be swift unless they occur close to the radiant or close to the horizon. There are also minor showers active during the Perseids that will also add a few meteors per hour to the total count.

If you would like to contribute more to our knowledge of the Perseids, then I invite you to get serious about meteor observing and to make an hourly count of the activity you witness. Other more detailed projects include the estimating the magnitude, velocity, and color of each meteor. Others also note whether there was a persistent train after the meteor has vanished. Meteor watching can be both fun and scientifically useful endeavor. To be scientifically useful you must share your data with an active meteor organization such as the the AMS. We accept data from observers with all levels of experience. The easiest way to send in observations is to email your data to our visual coordinator Kim Youmans. We look forward to hearing from you!

From earliest times, humankind has noticed flurries of meteors that seemed to emanate from points in the sky at particular times of the year. These flurries, now called meteor showers, are produced by small fragments of cosmic debris entering the earth's atmosphere at extremely high speed. Each time a comet swings by the sun, it produces large amounts of small particles which will eventually spread out along the entire orbit of the comet to form a meteoroid "stream." If the Earth's orbit and the comet's orbit intersect at some point, then the Earth will pass through this stream for a few days at roughly the same time each year, producing a meteor shower.

The peak of the 1997 Leonid meteor shower as seen from ABOVE, in Earth orbit, by the MSX satellite. 29 meteors were imaged over a 48 minute period entering the Earth's atmosphere. Note the roughly parallel paths followed by the meteors, with the entry angle increasing slightly over the period of the time exposure. Compare this figure to the one the top of this page, which shows how the shower appears from BELOW. (image courtesy of Peter Jenniskens)

Because meteor shower particles are all traveling in parallel paths (see the figure above), and at the same velocity, they will all appear to radiate from a single point in the sky to an observer below (see the figure at the top of the page). This radiant point is caused by the effect of perspective, similar to railroad tracks converging at a single vanishing point on the horizon when viewed from the middle of the tracks. This effect is illustrated in the photograph shown above. Meteors seen near the radiant are approaching the observer and will appear as short streaks in the sky. Meteors seen 45 to 135 degrees from the radiant are moving in a more parallel direction to the observer. These meteors will produce longer streaks in the sky. Those seen in excess of 90 degrees from the radiant are actually moving away from the observer and their paths will again shorten the further the are from the radiant.

Meteor showers are usually named for the constellation in which their radiant lies at the time of shower maximum. Thus, the Perseid meteor shower (peaking about August 12) will appear to radiate from the constellation of Perseus, while the Leonid meteor shower (peaking about November 18) will appear to radiate from the constellation Leo.

Specific suggestions for observing meteor showers may be found on our Visual Observing Program page.

The meteor showers discussed below recur each year; in some cases they have been recognized for hundreds of years. The name of the shower in most cases indicates the constellation from which the meteors appear. Also discussed are sporadic rates. Sporadic meteors are those random meteors not associated with a particular shower; they are the random detritus left over from the creation of the solar system or are old dispersed debris not recognizable today as shower meteors. Click on the shower names (when linked) for more detail on any given shower. For meteor observers, those located in the northern hemisphere have a distinct advantage as shower activity is stronger there than that seen by observers located south of the equator. The reason for this is that most of the major showers have meteors that strike the Earth in areas located far above the equator. As seen from the northern hemisphere these meteors would appear to rain down from high in the sky in all directions. From those situated in the southern hemisphere only a small percentage of this activity is visible. Any activity would appear to travel upwards from radiants located low in the sky.

There are a few meteor showers best seen from the southern hemisphere. These would include any radiant with a declination (celestial latitude) below -20 and those that reach maximum activity during the southern hemisphere's winter months (July-August-September). These showers would include the Alpha Centaurids, Gamma Normids, Pi Puppids, Piscis Austrinids, Delta Aquarids, Alpha Capricornids, Dec Phoenicids, and the Puppid/Velids.

The year begins with the intense but brief Quadrantid maximum (January 3/4). Its brevity combined with typically poor winter weather hampers observation. January overall has good meteor rates restricted to the last third of the night. Rates to 20/hour can be obtained. A large number of radiants spread along the ecliptic from Cancer to Virgo. This activity diminishes somewhat in February with the same areas active.

Late-night rates are fair in the first half of March, but become poor rather suddenly after mid-March. The very poor rates, seldom reaching 10/hour, continue into early June. However, two major showers appear in this interval. The Lyrids past mid-April (max: April 22/23) raise meteor rates for several nights. The Eta Aquarids (max: May 7/8) enrich late nights of May's first half, sometimes substantially.

February, March, and April evenings have another notable feature. An unusual number of sporadic fireballs come in this interval, possibly one every few nights.

June to mid-July has fair rates. The last half of July has rates increasing steadily as the Delta Aquarids (July 29/30) and Alpha Capricornids (July 27-28) have maxima at month's end. Even the Perseids are beginning to show a little.

Overall, late July to mid-August is very rich in meteors. The Perseid maximum, just before mid-August (August 12/13), is fairly prolonged and quite rich.

High sporadic activity after midnight continues for the rest of the year, but especially in September and the first half of December. Sporadic rates over 20/hour are possible for this entire interval. September radiants are numerous in Aries and Taurus.

Mid-October to mid-December is a nearly continuous period of heavy meteor activity. The Orionids (max: October 21/22) during the second half of October have a prolonged, plateau maximum for several nights, usually rich. The Taurids (max: October 11 for S. Taurids, November 13/14 for N. Taurids), active for two months, are most numerous in November's first half, and can be rather variable in strength. This period is the best for a couple of Taurid fireballs each night, if the shower is not too weak. The Leonids of mid-November (max: November 17-19) are quite unpredictable, with rich displays occuring roughly every 33 years. The last Leonid storm period occurred from 1998 through 2002. Studies have shown that no Leonid storms will occur in either 2033 or 2066. We will have to wait until 2099 for a return of the activity recently seen during the past few years.

Finally the Geminids of mid-December (max: December 13/14) climax the year with the strongest dependable and observable display. Geminid rates usually pass 60-70/hour at maximum. Concurrent activity from Leo and Canis Minor is also notable during the Geminids. Finally, the oft-overlooked Ursids complete the year's activity, reaching maximum on December 22/23. Nearly half the year's visual meteor activity is crammed into the two-month interval just described.