(meteorobs) Meteor Activity Outlook for August 4-10, 2012

[Robert Lunsford]

Meteor activity kicks into high gear in August as seen from the northern hemisphere. The main reason for all this activity is the Perseid shower that peaks on August 12. This shower is active most of the month and remains above the level of the sporadic background for a week centered on August 12. The sporadic activity is also near maximum as seen from the northern hemisphere and is now more than double the rates from just three months ago. As seen from south of the equator, meteor rates are still decent but falling rapidly. The sporadic rates continue their downward slide and the Perseid radiant does not rise high into the sky as seen in the southern hemisphere so rates from this shower are greatly reduced when compared to the northern hemisphere.

During this period the moon reaches its last quarter phase on Thursday August 9th. This weekend the bright waning gibbous moon will rise during the late evening hours and will effectively ruin the sky for meteor watching the remainder of the night. The estimated total hourly rates for evening observers this week is near four for observers located in the northern hemisphere and two for observers south of the equator. For morning observers the estimated total hourly rates should be near fifteen for those located in the mid-northern hemisphere (45 N) and ten for those viewing from the mid-southern hemisphere (45 S). Locations between these two extremes would see activity between the listed figures. These rates assume that you are watching from rural areas away from all sources of light pollution. 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. Morning rates are reduced during this period due to the intense moonlight.

The radiant (the area of the sky where meteors appear to shoot from) positions and rates listed below are exact for Saturday night/Sunday morning August 4/5. These positions do not change greatly day to day so the listed coordinates may be used during this entire period. Most star atlases (available at science stores and planetariums) will provide maps with grid lines of the celestial coordinates so that you may find out exactly where these positions are located in the sky. A planisphere or computer planetarium program is also useful in showing the sky at any time of night on any date of the year. Activity from each radiant is best seen when it is positioned highest in the sky, either due north or south along the meridian, depending on your latitude. It must be remembered that meteor activity is rarely seen at the radiant position. Rather they shoot outwards from the radiant so it is best to center your field of view so that the radiant lies at the edge and not the center. Viewing there will allow you to easily trace the path of each meteor back to the radiant (if it is a shower member) or in another direction if it is a sporadic. Meteor activity is not seen from radiants that are located below the horizon. The positions below are listed in a west to east manner in order of right ascension (celestial longitude). The positions listed first are located further west therefore are accessible earlier in the night while those listed further down the list rise later in the night.

The list below presents a summary of the expected activity this week. Rates and positions are exact for Saturday night/Sunday morning August 4/5, but may be used all week. The full descriptions of each radiant will continue next week when the moon becomes less of a nuisance to observers.

Kappa Cygnids (KCG) - 18:06 (274) +46   Velocity 23km/sec
Northern Hemisphere - <1 per hr    Southern Hemisphere - <1 per hour

Alpha Capricornids (CAP) - 20:36 (309) -09   Velocity 25km/sec
Northern Hemisphere - 1 per hr    Southern Hemisphere - 1 per hour

Antihelions (ANT) - 21:40 (325) -12   Velocity 30km/sec
Northern Hemisphere - <1 per hr   Southern Hemisphere - 1 per hour

Delta Aquariids (SDA) - 22:42 (346) -14   Velocity 42km/sec
Northern Hemisphere - 2 per hr   Southern Hemisphere - 3 per hour

Piscids Austrinids (PAU) - 23:12 (348) -27   Velocity 35km/sec
Northern Hemisphere - <1 per hr   Southern Hemisphere - 1 per hour

Perseids (PER) - 02:28 (037) +56   Velocity 61km/sec
Northern Hemisphere - 6 per hr   Southern Hemisphere - 3 per hour

Alpha Triangulids (ATR) - 02:40 (040) +37   Velocity 67km/sec
Northern Hemisphere - <1 per hr   Southern Hemisphere - <1 per hour

Eta Eridanids (ERI) - 02:52 (043) -13   Velocity 64km/sec
Northern Hemisphere - <1 per hr   Southern Hemisphere - <1 per hour

Clear Skies!
Robert Lunsford
American Meteor Society