Planets may occult the same star only a few times because of the star's rapid proper motion. Over the long haul, even gravitational perturbations will affect planetary orbital stability. When considering lunar occultation of planets, although more than 200 events occur on average per century per planet, many are not visible. Some occur during daylight while others are visible over small geographical area since the events may not be central to the moon's equatorial axis. Still other types of events, such as certain planet-on-planet occultations will occur several times over a relatively short period only to return after gaps of several millennia.

Table 2.1: Moon-Star Occultation Frequency by MagnitudeThe average worldwide frequency of lunar-stellar occultations based on a 19 year average. Bright star occultations occur during occultation-seasons; when several years may elapse without an event.Star Mag. Frequency Star Mag. Frequency >=1 43.6 days >=5 16.6 hours >=2 23.0 days >=6 5.52 hours >=3 6.38 days >=7 1.92 hours >=4 2.26 days >=8 0.72 hour

Table 2.2: Planet-Star Occultations Frequency by Magnitude Worldwide (AVERAGE) years per eventThe average frequency of planet-star occultations by magnitude. Missing data indicates the event is either very rare or not readily visible.>=8th >=7th >=6th >=5th >=4th Mercury: 41.6 Years Venus: 21.7 Years Mars: 8.47 Years 29.4 Years 167 Years Jupiter: 4.62 Years 14.3 Years 62.5 Years Saturn: 18.5 Years 50.0 Years 250 Years Uranus: 71.4 Years 167 Years 250 Years 250 Years Neptune: 167 Years 500 Years

Table 2.3: Superior Planet-Bright Star (>=3rd Magnitude Conjunctions <= 60' for 100 Years Worldwide (AVERAGE) days or years per eventThe average worldwide average frequency of planet-star conjunctions with stars of 3rd magnitude or brighter as a function of separation. Percentages (observable conjunctions) are based on solar elongation of 15 or greater. Nearly all events will be visible to some extent although separation will be greater. Only Neptune will yield more events during the 21st century than on average over the next 600 years for separation <=10.LOCAL (AVG.) SEP <=60' SEP <=30' SEP <=10' Min. Sep Obs (%) Mars: 205 Days 351 Days 5.26 Years 43 Jupiter: 1.92 Years 2.78 Years 25.0 Years 50 Saturn 4.76 Years 12.5 Years 25.0 Years 19 Uranus: 11.1 Years 16.7 Years 33.3 Years 55 Neptune: 9.09 Years 12.5 Years 33.3 Years 45

Table 2.4: Planet-Bright Star Conjunctions <=10' for 600 Years (2000-2599) Worldwide (AVERAGE) years per eventLOCAL:(AVG.) SEP <=10' SEP <=5' SEP <=99" Min. Sep Obs (%) Mars: 4.80 Years 8.33 Years 30.0 Years 29 Jupiter: 21.4 Years 33.3 Years 120 Years 68 Saturn: 25.0 Years 46.2 Years 200 Years 50 Uranus: 28.6 Years 28.6 Years 85.7 Years 19 Neptune: 50.0 Years 100 Years >600 Years 42

Table 2.5: Planet-Star Conjunctions <= 90 arc seconds for 100 Years (2000-2099) Worldwide (AVERAGE) days or years per eventThe average frequency of planet-star conjunctions of stars of 8th magnitude or brighter as a function of separation. Percentages (observable conjunctions) are based on solar elongation of 10 degrees (except 15 degrees for Uranus and Neptune). Mars data applies for the years 2000-2024.LOCAL (AVG.) SEP <=90" SEP <=50" SEP <=10" Min. Sep Obs (%) Mars: 30.9 Days 54.8 Days 208 Days Jupiter: 156 Days 285 Days 5.00 Years 19 Saturn: 295 Days 1.72 Years 9.09 Years 23 Uranus: 2.00 Years 3.13 Years 20.0 Years 30 Neptune: 2.63 Years 4.55 Years 100 Years 60

Table 2.6: Planet-Star Conjunctions <=99 arc seconds vs. Magnitude Worldwide (AVERAGE) days or years per eventThe average frequency of planet-star very close conjunctions as a function of stellar magnitude. For stars 6th magnitude or brighter, data are based on 500 years; 100 years or less for 8th magnitude events, except 25 years for Mars.Separation: <=90" <=99" <=99" <=99" <=99" Stellar Mag.: >= 8th >=6th >=5th >=4th >=3rd Venus: Mars: 30.9 days 233 days 2.41 years 11.4 years 35.7 years Jupiter: 156 days 2.77 years 5.49 years 167 years 167 years Saturn: 295 days 4.72 years 17.9 years 33.3 years 250 years Uranus: 2.00 years 6.10 years 14.7 years 41.7 years 83.3 years Neptune: 2.63 years 17.8 years 21.7 years 55.6 years >500 years

Return to: Home Page

Go Back To: Chapter 1 (part 1)