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Updated November 19, 2011
TABLE OF METEOR SHOWERS, 2004
By M. Campbell-Brown and P. Brown
The table lists the major visual showers as well as those detectable by radio/radar methods during the day. The two showers expected to produce the best visual displays of the year are the Perseid and Geminid showers, conventionally taken to be among the three strongest along with the Quadrantid shower (which is heavily affected by moonlight in 2004). In 2004, the Perseid shower may also show heightened activity near 21h UT on Aug. 11 associated with meteoroids perturbed inward toward Earth’s orbit by Jupiter. The strength of this outburst activity is unclear; it might be comparable to the early maxima detected in the stream during the 1990s, suggesting that ZHRs in the range 100 to 200 are possible.
The column Max Date lists the date and hour (in Universal Time) when Earth intersects the densest part of the stream, based on the solar longitude λ (J2000.0) given in the fourth column. The fifth column, D, gives the duration of the shower in days, which is the total number of days for which the activity level is over half the maximum activity.
The ZHR, or Zenithal Hourly Rate, is given for the peak of the shower. The
The R column gives the local times for which the radiant is above the horizon for an observer at 43° N latitude (and therefore meteors from the shower are visible); a ü symbol indicates that the radiant is up throughout the night hours, while “day” indicates that the shower is not visible at night. The Moon column gives the percent illumination of the Moon at the time of the shower peak. The population index, r, at the time of the maximum is a measure of the size distribution of particles in the stream. A larger r value indicates an excess of small particles, while smaller r values indicate larger numbers of brighter meteors. A shower with a higher r value will therefore suffer more from background light such as moonlight or light pollution. Sporadic meteors at observable visual magnitudes have an r value near 3.0.
The RA and Dec are given in the next two columns: They give the position in the sky of the radiant at the time of the shower peak. The position of the radiant will vary from these values away from the time of the peak; tables published by the International Meteor Organization in their annual shower calendar provide details of radiant drift. The last column, v, gives the geocentric speed of the meteors in the shower.
Excerpted from the Observer's Handbook 2004 © The Royal Astronomical Society of Canada, 2003. Used with permission of The Royal Astronomical Society of Canada. The Observer's Handbook can be ordered at http://www.rasc.ca/publications.htm.