ALPO Meteors Section

Coordinator: Robert Lunsford
 
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.
[Image: Leonid Meteor Shower Radiant]

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Viewing Meteor Activity

Since meteors are a transient phenomena one cannot go outside at night and expect to see meteor activity. This is especially true during the evening hours when the Earth is moving in the opposite direction from the sky seen above during those hours. At this time of night meteoroids (meteors in space) must catch up to the Earth in order to enter the Earth's atmosphere. Therefore meteor rates are lowest near 1800 (6:00pm) local time. Conditions for viewing meteor activity improves as the night progresses. At midnight a great majority of the meteors seen strike the Earth from a perpendicular angle instead of from behind. These conditions offer better rates than witnessed early in the evening but the general activity is still low when compared to the morning hours. During the dark morning hours the Earth is rotating toward the direction it moves in space, known as the apex. During this time the Earth slams head-on into meteoroids and many more will be seen. This is much like a vehicle driving through the rain. More raindrops will strike the front windshield compared to the rear window. The peak meteor activity occurs near 0600.

In addition to the diurnal cycle there are also annual variations in the meteor activity. As seen from the mid-northern hemisphere the second half of the year is much more active than the first six months. The reason for this are several. First of all the sporadic (random) meteor activity is stronger during this period. Also most of the major annual showers active during the second half of the year have radiants located north of the celestial equator, favoring northern obserevers. The cycle seen from the mid-southern hemisphere is opposite with the better activity occurring during the first half of the year. Observers at the equator enjoy fair, but not exceptional activity all year long.

During certain times of the year the major meteor showers are active and increase the nightly activity severalfold. This is especially true if the moon is near its new phase and not brightening the nighttime sky. The list of these showers is provided below (see the class I showers).

This is also the best time to see fireballs, which are exceptionally bright meteors that can light the nighttime scene. These meteors can range from the light of the brightest planet Venus (magnitude -5) to that beyond the light produced by the full moon (magnitude >-13).


This double bursting fireball was photographed at 23:45 Universal Time on August 6, 2007 by Maurizio Eltri from central Venice, Italy. He estimated this sporadic (random) fireball to be of maximum magnitude -8, which is nearly as bright as the half moon. Picture courtesy of Maurizio Eltri, (Unione Astrofili Italiani Sezione Meteore).
[Image: Double Bursting Fireball]

To keep current on the upcoming meteor activity the Meteors Section invites you to subscribe to their quarterly newsletter, available for the price of postage (currently 44 cents per issue). To subscribe contact our section coordinator Robert Lunsford.


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Viewing Activity from the 2010 Lyrid Meteor Shower

Examples of Lyrid Activity

This chart represents plotted Lyrid meteors (arrows) seen from 40 degrees north latitude while facing north near 0500 local daylight time on April 22nd. This chart was created using SkyChart III Version 3.5.1 from Carina Software.


The Lyrids are active from April 16 through the 25th. Peak rates for this shower occur on the 22nd when rates can approach fifteen Lyrids per hour. Five Lyrids per hour can appear on the 21st and the 23rd. Away from these three nights, the Lyrids are weak, only producing 1-2 each hour.

At the time of maximum activity the Lyrid radiant is actually located in eastern Hercules, seven degrees southwest of the brilliant star Vega (Alpha Lyrae). This area of the sky lies below the horizon during the early evening hours. Therefore no Lyrid activity can be seen until the late evening hours. The radiant attains a decent elevation between midnight and 0100, depending on your latitude. It is best situated high in a dark sky just before the start of morning twilight. Your best rates will occur during the last dark hour before dawn.

On the night of maximum activity the moon will be just past its first quarter phase and will set between 0100 and 0200 local daylight time for most locations. Observers in the southern hemisphere will see very little Lyrid activity as the radiant will be located low in the northern sky. All Lyrid meteors will trace back to the radiant area in eastern Hercules. There will be other showers and random activity visible during this period so not all meteors will be members of the Lyrid shower. Lyrid meteors will appear to travel swiftly through the sky unless they are seen near the radiant or near the horizon. Lyrids seen there will move more slowly as they are moving towards you (if seen near the radiant) or away from you (if seen near the horizon). On occasion the Lyrids produce fireballs, meteors that exceed the brightness of the planet Venus (magnitude -4).

The Lyrids are particles from Comet Thatcher (C/1861 G1). This comet has an orbital period of 415 years and the last time it was a perihelion was back in 1861. This shower has produced several notable outbursts. These occurred in the years 1803, 1849, 1850, 1884, 1922, 1945, and 1982. The 1803 event seems to the strongest as rates exceeded 500 Lyrids per hour at maximum. The 1982 event was seen from eastern North America where rates were estimated near 100 per hour at maximum. I witnessed the final portions of this outburst as I drove out to dark sky site. At that time, Lyrid meteors were seen shooting upward from the northeastern horizon. Once I arrived at my site the outburst was over and very little activity was seen the remainder of the night. The next possible outburst for this shower is predicted to occur in 2040 and 2041.

If you would like to contribute more to our knowledge of the Lyrids 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 ALPO. We accept data from observers with all levels of experience. Our data is published in our quarterly newsletter. The easiest way to share your data is to email your results to our section coordinator Robert Lunsford. We look forward to hearing from you!


2009 Meteor Shower Calendar

Shower Activity Period Maximum Radiant Velocity r ZHR Class Moon
    Date S. L. R.A. Dec. km/s        
Antihelion Source (ANT) Dec 01-Sep 07 - - - - 30 3.0 3 II -
Quadrantids (QUA) Dec 26-Jan 13 Jan 03 283°16 15:20 +49° 42 2.1 120 I 6
Alpha Centaurids (ACE) Jan 28-Feb 21 Feb 07 319°2 14:00 -59° 56 2.0 5 II 12
Delta Leonids (DLE) Feb 15-Mar 10 Feb 25 336° 11:12 +16° 23 3.0 2 II 0
Gamma Normids (GNO) Feb 25-Mar 22 Mar 13 353° 16:36 -51° 56 2.4 4 II 16
Lyrids (LYR) Apr 16-Apr 27 Apr 23 033° 18:12 +33° 46 2.1 18 I 27
Pi Puppids (PPU) Apr 15-Apr 28 Apr 23 033°5 07:20 -45° 18 2.0 var III 27
Eta Aquarids (ETA) Apr 27-May 23 May 07 047° 22:36 -01° 68 2.4 60 I 12
Eta Lyrids (ELY) May 06-May 14 May 10 050° 19:22 +43° 43 3.0 3 II 15
June Bootids (JBO) Jun 22-Jul 02 Jun 27 095°7 14:56 +48° 18 2.2 var III 5
Piscis Austrinids (PAU) Jul 15-Aug 10 Jul 28 125° 22:44 -30° 35 3.2 5 II 7
Alpha Capricornids (CAP) Jul 12-Aug 08 Jul 28 125° 20:20 -10° 24 2.5 4 II 7
Delta Aquarids (SDA) Jul 21-Aug 30 Jul 30 127° 22:42 -17° 43 3.2 20 I 9
Perseids (PER) Jul 13-Aug 26 Aug 12 140° 03:12 +58° 59 2.6 100 I 20
Kappa Cygnids (KCG) Aug 03-Aug 25 Aug 17 145° 19:04 +59° 25 3.0 3 II 25
Alpha Aurigids (AUR) Aug 28-Sep 03 Sep 01 158°6 06:06 +39° 65 2.6 7 II 11
September Perseids (SPR) Sep 06-Sep 13 Sep 10 168° 03:12 +40° 65 2.9 5 II 19
Delta Aurigids (DAU) Sep 18-Oct 10 Sep 29 186° 05:52 +49° 64 2.9 2 II 13
Draconids (GIA) Oct 06-Oct 10 Oct 08 195°4 17:28 +54° 20 2.6 var III 18
Southern Taurids (STA) Sep 18-Nov 26 Oct 11 198° 02:18 +09° 29 2.3 5 II 21
Epsilon Geminids (EGE) Oct 14-Oct 24 Oct 20 207° 06:48 +28° 71 3.0 2 II 2
Orionids (ORI) Sep 28-Nov 10 Oct 21 208° 06:22 +16° 68 2.5 23 I 3
Leo Minorids (LMI) Oct 17-Oct 27 Oct 23 209° 10:40 +37° 61 2.7 2 II 4
Northern Taurids (NTA) Oct 20-Nov 30 Nov 13 231° 03:52 +22° 29 2.3 5 II 25
Leonids (LEO) Nov 07-Nov 28 Nov 18 236° 10:16 +22° 71 2.5 var III 1
Alpha Monocerotids (AMO) Nov 15-Nov 25 Nov 21 239°32 07:48 +01° 65 2.4 var III 4
Dec Phoenicids (PHO) Nov 28-Dec 09 Dec 06 254°25 01:12 -53° 18 2.8 var III 18
Puppid/Velids (PUP) Dec 01-Dec 15 Dec 07 255° 08:12 -45° 40 2.9 10 I 19
Monocerotids (MON) Dec 06-Dec 20 Dec 07 255° 06:32 +09° 41 3.0 2 II 10
Sigma Hydrids (HYD) Nov 22-Dec 23 Dec 09 257° 08:24 +03° 60 3.0 3 II 21
Geminids (GEM) Dec 03-Dec 19 Dec 14 262°2 07:36 +32° 35 2.6 120 I 26
Coma Berenicids (COM) Dec 10-Jan 27 Dec 19 268° 11:40 +25° 64 3.0 5 II 3
Ursids (URS) Dec 16-Dec 25 Dec 22 270°7 14:34 +75° 32 3.0 10 I 5

Information and Table Template Courtesy the International Meteor Organization.


Explanation of the 2009 Meteor Shower Calendar

Shower: named for the constellation or closest star within a constellation where the radiant is located at maximum activity.

Activity Period: the dates when the ZHR (Zenith Hourly Rates) are equal to or greater than one.

Maximum: the date on which the maximum activity is expected to occur.

S.L.: the equivalent solar longitude of the date of maximum activity. Solar longitude is measured in degrees (0-359) with 0 occurring at the exact moment of the spring equinox, 90 at the summer solstice, 180 at the autumnal equinox, and 270 at the winter solstice.

Radiant: the area in the sky where shower meteors seem to appear from. This position is given in right ascension (celestial longitude) and declination (celestial latitude).

Velocity: the velocity at which shower meteors strike the Earth's atmosphere. The velocity depends on the angle meteoroids (meteors in space) intersect the Earth. Meteoroids orbiting in the opposite direction of the Earth and striking the atmosphere head-on are much faster than those orbiting in the same direction as the Earth. This velocity is measured in kilometers per second.

r: The Population Index, An estimate of the ratio of the number of meteors in subsequent magnitude classes. Simply stated: the lower the "r" value, the resulting overall mean magnitude of each shower will be brighter. "r" usually ranges from 2.0 (bright) to 3.5 (faint).

ZHR: Zenith Hourly Rate, the average maximum number of shower meteors visible per hour if the radiant is located exactly overhead and the limiting magnitude equals +6.5. Actual counts rarely reach this figure as the zenith angle of the radiant is usually less and the limiting magnitude is usually lower. ZHR is a useful tool when comparing the actual observed rates between individual observers as it sets observing conditions for all to the same standards.

Class: A scale developed by Robert Lunsford to group meteor showers by their intensity:

Class I: the strongest annual showers with ZHR's normally ten or better.

Class II: reliable minor showers with ZHR's normally three or better.

Class III: showers with widely variable rates. They may be strong one year and totally inactive the next.

Class IV: weak minor showers with ZHR's rarely exceeding three. The study of these showers is best left to experienced observers who use plotting and angular velocity estimates to determine shower association. Observers with less experience are urged to limit their shower associations to showers with a rating of I to III. These showers are also good targets for video and photographic work.

Moon: the age of the moon in days where 0 is new, 7 is first quarter, 14 is full, and 21 is last quarter. Meteor activity is best seen in the absence of moonlight so showers reaching maximum activity when the moon is less than 10 days old or more than 25 are much more favorably observed than those situated closer to the full moon.