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Transit Motion Applet

The different views of the simulation:

Looking onto the ecliptic plane:

The Earth and Venus are moving couterclockwise around the Sun.

The orbital plane of Venus is inclined (by 3.39°) against the ecliptic plane. The grey part of Venus' orbit is below the ecliptic plane.

At the point D (Descending Node) Venus is passing the ecliptic plane from north to south, and at A (Ascending Node) from south to north.

This constellation (inferior conjunction and Venus passing a node) is a transit: Earth, Venus and Sun are in a straight line.

Looking parallel to the ecliptic plane

from D to A. Venus is seen within the disc of the sun (transit).

The actual inclination angle of Venus' orbital plane is only 3.39°, and 7.00° for Mercury.
Orbit eccentricity for:
Earth 0.0167
Venus 0.0067
Mercury 0.2056

Geocentric view

looking to the Sun from the moving Earth.

At inferior conjunction and passing a node Venus is seen within the disc of the Sun (transit).

The next figure traces the geocentric path of Venus starting from an inferior conjunction (transit) over a time interval of 4 years, ending by a superior conjunction (Venus is behind the Sun). There are 13 node passages of Venus:

Choose from the time interval menu to get this drawing.

The out most horizontal distance between the Sun and Venus is determined by the maximum elongation angle (46° neglecting the small orbit eccentricity of the Earth and Venus):

The maximum vertical angle may be up to 9.6° for Venus, and 6° for Mercury. To see a transit this angle must be smaller than 0,25° (radius of the Sun), i.e. Venus has to pass a node.

The geocentric path of Venus starting from an inferior conjunction during a time interval of 8 years ends by another inferior conjunction (transit):

The (sidereal) orbit period of Venus is TV=224.701 days, and TE=365.256 days for the Earth. The time interval T between two inferior conjunctions is:

1/T = 1/TV- 1/TE or T = TVTE/(TV-TE) = 583.92 days

After 8 years Venus will be back at the starting point with a difference of only 2.5 days:

5 x 583.92    d = 2,919.6  d
8 x 365.25636 d = 2,922.05 d

The coincidence is better after a period of 243 years:

152 x 583.92    d = 88,755.8 d
243 x 365.25636 d = 88,757.3 d

Four transits will happen within 243 years following a transit:

8 years + 121 1/2 years + 8 years + 105 1/2 years = 243 years

5 syn. per. + 76 syn. per. + 5 syn. per. + 66 syn. per. = 152 synodic periods

Use to check out.

 Web Links Transits of Venus (Peter M Langford) In fact there is a rather curious pattern to transits of Venus and the purpose of this article is to explore why.

Last modified: 2012, Apr 15