Leap Day

Types of Year:

Calendar- 365 days (calculated by crop and planting cycles)

Tropical- 365.2422aka Mean solar year, corresponds to the cycle of the seasons. (based on the equinoxes)

Siderial- 365.256 days (period of earth in orbit with respect to the stars)

Synodic- relative alignment

Computing the synodic year for Mars.

Mars' Sidereal year 1.881 Years

The 4th planet from the sun revolves: 0.128 times that of Mercury, 0.327 times Venus, 0.532 times Earth, 6.31 times faster than Jupiter, 15.66 times Saturn, 44.67 times Uranus, and 87.61 times Neptune.

Mars' Synodic year 2 Years + 1 to 2.5 Months

Interval (779.7 days) when Mars reaches opposition. The synodic period (opposition to opposition) occurs 764 days near perihelion and about 811 days near aphelion. On average, Mars is in retrograde 73 days centered on opposition. During this period, Mars' movement forms a loop near 9 hours and 21 hours R.A. and a zigzag paths near 3 hours and 15 hours R.A. Next oppositions will occur: 13 Jun 2001 (20.8") and 28 Aug 2003 (25.1"). Oppositions occurring in August (during this epoch) are the most favorable; with Mars' brightness exceeding Jupiter's. Extreme brightness range at oppositions is -1.2 to nearly -3.0 which correlates to the planet's apparent size. At aphelion oppositions, the planet's size can be as small as 14".

In Class Exercise:

Add a leap year every 4 years
but, when year is divisible by 100 DON'T add
but, when year is divisible by 400 add
but, when year is divisible by 3200 DON'T add
but, when year is divisible by 80000 add

Back to the homepage!