2001 Leonid Meteor Storm

Leonids2001Radiant20(500)0115ps.jpg (108010 bytes)

The Leonid meteor shower occurs annually around November 17 or 18.  Meteor showers are named after the constellation where the radiant is located, which is the point in the sky from which the meteors appear to originate.  Hence, the Leonid radiant is in the constellation Leo.   The Leonid meteors are created by bits of debris originating from Comet Temple-Tuttle passing through our atmosphere at about 70 km/sec.  Most years there is a modest level of activity, with perhaps a dozen meteors per hour visible at its peak.  Comet Temple-Tuttle orbits the Sun every 33 years, and in years when Comet Temple-Tuttle is near the Sun, there may be a dramatic display of Leonid meteors called a "storm," which is defined as a Zenithal Hourly Rate (ZHR) of 1,000 meteors/hr or more.  The Leonid storm of 1966 was one of the greatest in history, with a peak ZHR of about 100,000.  Comet Temple-Tuttle reached perihelion (closest approach to the Sun) in February 1998, and the 1998 Leonids were characterized by a fireball display of unusually bright meteors peaking at a ZHR of about 350.  In 1999, observers in western Asia, Europe, and northern Africa witnessed a storm, with activity peaking at a ZHR of about 3500.  In 2000, observations were hampered by bright moonlight.  2001 promised better viewing conditions, with the Moon setting soon after the Sun on November 17 and 18.  Two storm-level peaks were forecast:  the first, at about 10:00 UT on November 18, favored observers in North America, and the second, at about 18:00 UT, favored observers in East Asia and Australia.

At the Riverside Astronomical Society's observing site in Landers, California, there were partly cloudy skies on the evening of November 17.  As Leo rose over the eastern horizon, more clouds moved in from the west until only a small portion of sky was free of clouds around 1:00 AM PST (9:00 UT) on November 18.  The sky then began to clear to the north, east, and south, and meteor activity began increasing noticeably between 1:00 and 2:00.  Activity appeared to peak at about 10-20/min. between 2:30 and 3:00 PST (10:30 and 11:00 UT), then gradually diminished until dawn.  The International Meteor Society estimates that the first peak ZHR was about 1400/hr. at 10:30 UT, with the second peak ZHR about 2600/hr. at 18:20 UT.

The above image is a composite of 15 separate 5-minute exposures.  About two dozen meteors can be identified in the image.  The "sickle" asterism of Leo, where the radiant is located, is at the center, facing the top of the image.  Jupiter is the bright object at top center in the constellation Gemini near the bright fireball.  M44, the Beehive Cluster, is located between Jupiter and Regulus which forms the base of the sickle.  The triangular glow at bottom center is the zodiacal light, created by dust in the plane of the ecliptic reflecting light from the Sun.

Instrument:   Nikon 20mm/2.8 lens, on a G-11 mount
  15 x 5 minutes
  Ektachrome P1600
  November 18, 2001, exposures taken between approximately 2:15 and 4:30 AM PST (10:15 and 12:30 UT)
  Landers, California, USA
Technical Notes:  Contrast and anti-vignetting adjustments were made to each exposure.  I had repositioned the camera after the seventh exposure, so I made two separate composites using Registar, one with the first seven exposures and the other with the remaining eight.  The two composites were then composited to make a third composite, and then the individual exposures were added as layers in Photoshop using the Lighten function to create the final image. A slight difference in contrast between the two composites used to create the final image is detectable at the bottom of the image.

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