SJAA Ephemeris April 2000 | SJAA Home | Contents | Previous | Next

Meteors

The Lurid Lyrids of April and Other Showers

Jane Houston Jones


DurationApril 16-25
MaximumApril 21-22
Hourly Rate10*
RadiantRA=18.1 hours DECL=+33 degrees
Solar Longitude at Maximum32.1 degrees
Atmospheric Velocity49km per second
Average Magnitude2.4
Persistent Trains15%
Radiant DriftRA =+1.1 DECL=0 deg.
*On several occasions this stream will unexpectedly produce hourly rates of over 100 meteors per hour.

Image produced by Gary Kronk using Starry Night 2.0 and Adobe Photoshop 5.0. It represents the view from mid-northern latitudes at about 4:30 a.m. local time around April 23.
The point from where the Lyrid meteors appear to radiate is located east of the constellation Lyra and is referred to as the radiant.

The Lyrids are visible through most of the night, with the radiant rising around 9 p.m. (local time). This year, a bright 85-90% moon just past full will illuminate the sky. Not the best meteor observing conditions, unfortunately. The radiant is located high in the morning sky around 4:00 a.m., with an altitude of about 75 degrees. The chart shows Cygnus and Lyra and the bright stars Altair, Lyra and Deneb, our herald of the summer yet to come. Although Cygnus is the more prominent and well-known of the two constellations, Lyra contains the bright star Vega, which outshines all other stars in that area of the sky.

To best observe the Lyrids wear appropriate clothing for the weather and lay outside in a reclining lawn chair for best, comfortable viewing. Late in the evening it would be best to lay with your feet pointing towards the east and look straight up. During the morning hours, as the radiant gets higher, you could point your feet towards the north, west, or south and adjust your line of sight to about 50 to 60 degrees above the horizon. It is generally not advised to look directly at the radiant, because meteors will not move much and fainter ones might be missed.

When you see a meteor mentally trace it backwards and if you arrive near Lyra it is probably a Lyrid. Meteor observing is great fun in groups. Try arranging a group of lawn chairs and have each observer observe a different quadrant of the sky. This will be great practice for the Perseid Shower in August.

Minor April Shower Activity
RadiantDurationMaximum
Tau DraconidsMar 13-Apr 17Mar. 31-Apr. 2
LibridsMar 11-May 5Apr. 17/18
Delta PavonidsMar 21-Apr 8Apr. 5/6
Pi Puppids (PPU)April 18-25Apr. 23/24

The duration of this shower extends from April 18 to April 25. The short-duration maximum occurs during April 23-24, from a radiant of RA=112 deg, DECL=-43 deg. The shower is associated with the periodic comet Grigg-Skjellerup. Although this comet was officially discovered in 1902, it was only recently perturbed by Jupiter into a close-approach orbit with Earth. Activity was first noted in 1972, and visual hourly rates of 18 to 42 meteors per hour were noted during the comet's perihelion returns of 1977 and 1982. Activity levels are typically very low or nonexistent in other years.

April UrsidsMar 18-May 9Apr 19/20
Alpha VirginidsMar 10-May 6Apr 7-18

Typical of streams lying near the ecliptic, the Alpha Virginids show evidence of a long duration-spanning from March 10 to May 6-and a diffuse radiant. Maximum hourly rates typically reach between 5 and 10 during April 7 to 18, with the average radiant being RA=204 deg, DECL=-11 deg. The meteors are generally slow.

April VirginidsApril 1-16Apr. 7/8
Gamma VirginidsApril 5-21Apr. 14/15


Mail to: Jane Houston Jones
Copyright © 2000 San Jose Astronomical Association
Last updated: July 19, 2007

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