The Meteor Activity Outlook is a weekly summary of expected meteor activity written by Robert Lunsford, Operations Manager of the American Meteor Society and contributor to this blog. The original unedited version of this week’s Meteor Activity Outlook can be found at the American Meteor Society’s site.
Meteor activity picks up a bit during April as two major showers are active during the month. The first of these, the Lyrids, are active from the 16th through the 25th, with a pronounced maximum on the 22nd. The Eta Aquariids start appearing near the 28th and reach maximum activity during the first week in May. Sporadic rates are low but steady as seen from the mid-northern hemisphere (45 N). Sporadic rates seen from the mid-southern hemisphere (45 S) rise this month toward a maximum in July.
During this period the moon reaches its first quarter phase on Wednesday April21st . At this time the moon lies ninety degrees east of the sun and sets near 0100 local daylight time (LDT), depending on your location. This weekend the waxing crescent moon will set shortly after the end of evening twilight and will not cause any inteference to meteor observers. The estimated total hourly rates for evening observers this week is ~2 for those in the northern hemisphere and ~3 for those south of the equator. For morning observers the estimated total hourly rates should be ~10 from the northern hemisphere and ~15 as seen from the southern hemisphere. The actual rates will also depend on factors such as personal light and motion perception, local weather conditions, alertness and experience in watching meteor activity.
The radiant positions and rates listed below are exact for Saturday night/Sunday morning April 17/18. These positions do not change greatly day to day so the listed coordinates may be used during this entire period.
The following showers are expected to be active this week:
Pi Puppids (PPU)
The elusive Pi Puppids (PPU) are now active from a radiant located at 07:12 (108) -46. This area of the sky lies in western Puppis near the double star Iota Puppi. This radiant is best placed as soon as it becomes dark as it culminates during the afternoon hours when the sun is still above the horizon. These meteors are nearly non-existent away from the night of April 23rd. Even on that night it would be lucky to spot just one, especially from the northern hemisphere, where the radiant lies low in the southwest at dusk. This shower has produced outbursts in the past so it should be monitored whenever possible, especially from the southern hemisphere. With an entry velocity of only 18 km/sec., the average Pi Puppid meteor would crawl through the sky at a snails pace.
Sigma Leonids (SLE)
The team of Sirko Molau and Juergen Rendtel have discovered a weak radiant active at this time in the constellation of Virgo. Video data shows that the Sigma Leonids (SLE) are active from April 18th through the 25th with maximum activity falling on the evening of April 21st (22nd UT). The radiant is currently located at 13:16 (199) +05. This position lies in central Virgo, five degrees northeast of the third magnitude star Delta Virginis. The radiant is best placed near midnight LDT, when it lies highest above the horizon. At 20km/sec. the Sigma Leonids would produce obvious, slow meteors. Expected rates are less than one per hour no matter your location.
h Virginids (HVR)
There is also a second new radiant active in Virgo this time of year. Video data shows that the h Virginids (HVR) are active from April 22-25 with maximum activity occurring on the 22nd. On the evening of the 21st (22nd UT), the radiant is currently located at 14:16 (220) -16. This position lies on the Virgo/Libra border, two degrees southeast of the fourth magnitude star Kappa Virginis. The radiant is best placed near 0200 LDT, when it lies on the meridian and is highest above the horizon. At 24km/sec. the h Virginids would produce more obvious, slow meteors. Expected rates would also be less than one per hour no matter your location.
The wide Antihelion (ANT) radiant is now centered at 14:40 (214) -13. This area of the sky lies in western Libra, three degrees west of the second magnitude star Zubenelgenubi (Alpha Librae). This radiant is best placed near 0200 local daylight time (LDT) when it lies on the meridian and is located highest in the sky. Due to the large size of this radiant, any meteor radiating from eastern Hydra, Libra, or eastern Virgo could be a candidate for this shower. Rates at this time should be near two per hour no matter your location. With an entry velocity of 30 km/sec., the average Antihelion meteor would be of medium-slow speed.
The major shower known as the Lyrids (LYR) are active from April 16th through the 25th. Maximum activity occurs on the morning of April 22th. The radiant is currently located at 18:00 (270) +35. This position actually lies in eastern Hercules, eight degrees southwest of the brilliant blue-white zero magnitude magnitude star known as Vega (Alpha Lyrae). The radiant is best placed during the last dark hour before dawn, when it lies highest above the horizon. At 48km/sec. the Lyrids would produce meteors of medium velocity. Expected rates this weekend are near one per hour during the last dark hour before dawn. At maximum, hourly rate between 10-20 can be expected. Due to the northerly declination of the radiant, these meteors are not well seen from high southern latitudes.
Nu Cygnids (NCY)
The team of Sirko Molau and Juergen Rendtel have a third weak radiant active at this time in the constellation of Cygnus. Video data shows that the Nu Cygnids (NCY) are active from April 18th through May 7th. Maximum activity occurs on the morning of April 20th. The radiant is currently located at 20:08 (302) +38. This position lies in central Cygnus, four degrees southwest of the second magnitude star Sadr (Gamma Cygni). The radiant is best placed during the last dark hour before dawn, when it lies highest above the horizon in a dark sky. At 42km/sec. the Nu Cygnids would produce meteors of medium velocity. Expected rates are near one per hour during the last dark hour before dawn. Due to the northerly declination of the
radiant, these meteors are not well seen from south of the equator.
The list below presents a condensed version of the expected activity this week. Rates and positions are exact for Saturday night/Sunday morning.
Shower Name RA DEC Vel Rates km/s NH SH PPU Pi Puppids 07h 12m -46 18 <1 <1 SLE Sigma Leonids 13h 16m +05 20 <1 <1 HVR h Virginids 14h 16m -11 24 <1 <1 ANT Antihelions 14h 40m -16 30 1 2 LYR Lyrids 18h 00m +35 48 1 <1 NCY Nu Cygnids 20h 08m +38 42 1 <1 RA - Right Ascension DEC - Declination Vel - Velocity relative to Earth (in km per sec) Rates - Rate of visible meteors per hour from a dark site NH - Northern Hemisphere SH - Southern Hemisphere