GEMINID METEOR SHOWER

The annual Geminid meteor shower might bring some excitement starting the midnight and to the early morning hours of coming Monday-Tuesday (13-14/12/2004).

Rates of 20 meteors an hour are considered good, however this year, predictions of rates of around 100 meteors per-hour are being estimated for those lucky enough to be awake during those hours and of course in the right region. The prediction is that North America may be more suitable for the high rate than the others. The other areas may see the shower, such as Asia, Africa, and Europe, but it will be during early morning hours or it could be around sunrise time.

The peak is expected to be between 1:20 am and 4:30 am for the Saudi Arabia. We may observe between 30 to 40 meteors per hour in our area provided we choose a dark area, weather permitting, and away from man made light pollution. Make sure to start observing about 2 hours earlier so as not to miss a thing.

For more detailed information you may visit my homepage: faculty.kfupm.edu.sa/PHYS/alshukri

Or send an email to alshukri@kfupm.edu.sa.

Check out the following links for complete information, observing tips and charts :

The Geminid Meteor Shower at www.kcbd.com/Global/story.asp?S=2674666

Strong Meteor Shower Peaks Monday Night : story.news.yahoo.com/news?tmpl=story&cid=96&ncid=753&e=10&u=/space/20041210/sc_space/strongmeteorshowerpeaksmondaynight
The 2004 Geminid Meteor Shower : www.yubanet.com/artman/publish/article_15953.shtml
Meteor shower predicted : taree.yourguide.com.au/detail.asp?class=news&subclass=local&category=general news&story_id=356079&y=2004&m=12
IMO Meteor Shower Calendar 2004 : <www.imo.net/calendar/cal04.html

The following article which I wrote in 2002 may give you more information about meteor showers:

Dr. Ali Mohammad Al-Shukri - Physics Department, King Fahd University Of Pertoleum And Minerals

Geminid Meteor Shower

A comet is a celestial body consists of frozen water, gasses, and dust. As it approaches the sun during its journey around it, the comet will be heated up and some of its outer part will be evaporated by the solar heat and radiation and a tail or more of gas and dust will be formed. Short period comets spend most of their time in the solar vicinity, which are constantly subjected to gravitational tidal forces of planets especially giant ones such as Jupiter and Saturn which may lead to their decay or disintegration and continual lose of their mass in a fast rate. The leftover debris continues to move in the same orbit, but due to solar wind and perturbations from the planets they will disperse in much wider area. Comets leave behind the evaporated dust particles during their close approach to the solar vicinity in the course of their journey around the sun.

Those debris move in the same orbit around the sun. Those particles will be scattered in a form as a stream around the entire orbit. Also some asteroid may shed some dust as it orbits the sun

In a course of a year as earth moves in its orbit around the sun, it crosses with orbits of many periodic comets (or strangely some times asteroids). That passage causes the comets (asteroid) debris of dust and gas to enter the earth's upper atmosphere and at high speeds (typical speed ranges from 20 to 50 kilometers per second and it may be as high as 70 km/hr.). The outcome is streaks or trails of lights as a result of igniting and burning and vaporizing or exploding of those materials due to friction with the atmospheric constituent. The phenomenon is called a meteor shower if there are few to tens of those lines of light per hour. On the other hand if the number is in the range of hundreds to thousands per hour or more it is called a meteor storm. A single streak of light is called a shooting or falling star. Meteor showers are named for the constellation that is seen in the region where apparently those meteors are radiated from. It is similar to the case of driving at high speed in a rainy day where you notice as you look in front of you that rain streams are rushing toward you as if it is radiating from a point in the direction of motion. Of course this is not true, the rain is falling vertically down word, but the relative velocities create such phenomena. The Earth is regularly bombarded with material from outer space and a meteor that does not belong to an identified meteor shower, which may come from any direction and at any time, is called a sporadic meteor. An extremely bright meteor is called a fireball. A meteor that explodes along its track is called a bolide. The size and brightness of those streaks of light differ depending on the size, composition, and the speed of those particles (object ranges in size from rocks down to extremely tiny grains). Some may partially survive and fall on the ground as meteoroids. It is estimated that several millions of kilograms of materials are deposited on the earth surface each year, mostly as dust.

During December 7-17 every year a meteor shower (tens of streaks of lights per hour) is expected, assuming the debris collective motion and spread are as predicted, as earth crosses the debris of Asteroid 3200 Phaethon while the asteroid is near the crossing point either ahead or behind of it, where it sheds off some of its dust due to solar heat and wind. The meteor shower associated with Asteroid 3200 Phaethon is radiated from Gemini constellation therefore it is called Geminid meteor shower or simply Geminids.

December 13-14 of 2004 is expected to be good a candidate date for Geminid meteor shower. Lack of information about the amount of material added to the stream and the perturbation on it by recent passages of the asteroid through that region, the inconsistencies within the dust shed by and the size of the asteroid, and degree of the spread and dispersion of the debris in addition to effects of planetary perturbations and solar radiation pressure led scientists to develop several diverse theoretical models which put the rate of the shower or storm for 2004 between 100 to 200 meteors per hour. This rate is called Zenithal Hourly Rate (ZHR) and it gives the hourly rate of the shower in a clear sky for the case of radiant is directly over head, at zenith and away from light pollution. Even though the predictions of peek rate and timing are most difficult, matching the theoretical models with past records of data of the maximum magnitude of the storms, the dates of the past perihelion (the closest approach to the sun) passages of the asteroid (it adds some additional material to the stream during each passage), and the knowledge of previous activity profile, let scientists to put the estimated maximum ZHR to less than 150 and may be closer to 100, but definitely not less than 50. And the predicted peek time of the Geminid meteor shower is estimated to occur at 1::20 a.m. on 14 December 2004 according to Saudi Arabian time when earth begins to enter the dense region of the comet's debris (head on collision between the earth and the debris). During that moment, as earth crosses the orbit of the asteroid, North America will be on the side of the earth that is in direct collision with those particles with the peak of the shower lasting few hours, But still people in Europe, Africa, and Asia can see less intense shower of about 50 meteors per hour, but you need to choose a dark area with clear sky. Please note as mentioned above the diversity of conditions may force the show to go either way.

If you are interested, dress appropriately for the weather and just be prepared to choose a dark area away from all city lights and obstacles. Then start at about midnight (1:00 a.m. to 4:00 a.m. may be the best time) looking up towards the east in the area of Geminid constellation, as it rises from the east,. Try not to concentrate only on the small area of the radiant. A Geminid meteor starts at the upper left part of the constellation, but it may be visible to the naked eye as it moves away. Therefore, try to look in different directions, at least to keep your neck away from stress and strain. You may continue looking and counting those meteors to just before the sunrise time. Form time to time an isolated shooting star may appear anywhere in the sky; it is called a sporadic meteor. Another way to observe meteor showers is by using a simple multi-banded radio. Usually meteor showers re-enforce radio signals due to bouncing the signals off the meteors, therefore one of the ways to observe meteor activities is to tone to a far away station of a very weak signal and listen to any random re-enforcement of the signals.

Meteor showers take place in the higher atmosphere and present no danger except, of course if part of it is survived and hit the surface of the earth as a meteorite, but that is infrequent and hitting a particular location is very rare. Unfortunately, it is not the case for upper atmosphere and outer space. Therefore satellite operators are concerned that even small impacts could impair some of the 600 operational satellites orbiting the earth and may short-circuit their sensitive sensors. NASA, the U.S. Air Force, and the University of Western Ontario in London, Ontario and other organizations will coordinate a team that helps track changes in the shower that could be a storm. Meteor Storms may cause a potential threat and risk to NASA and U.S. Air Force spacecraft and satellites. A worldwide network of radar and optical observation sites were made available for monitoring the storm. In reducing the impact effect to the satellites, their solar panels (arrays) are aligned parallel to the incoming debris stream. See the Constellation figure at the end of this article.

For more detailed information you may visit my homepage: faculty.kfupm.edu.sa/PHYS/alshukri

Or send an email to alshukri@kfupm.edu.sa.

Also you may visit the following sites for additional information about meteor showers:

1) http://aio.arc.nasa.gov/

2) International Meteor Organization at http://www.imo.net/

3) Jordanian Astronomical Society http://www.jas.org.jo

Kindly send me an email (alshukri@kfupm.edu.sa) or a fax (860-2293) regarding your observations including the following information for each observing period: Date and time, number of meteors observed, total time, location, and direction.

Your comments and suggestions are welcomed.

Dr. Ali Mohammad Al-Shukri, Assistant Professor, Physics Department, KFUPM,, Phone 860-2255, Fax 860-2293, KFUPM Box # 378, Dhahran 31262, Saudi Arabia