Clive mentioned the peculiar periodicity - 8 years, 121.5 years, 8
years and 105.5 years.
There is this further peculiarity - two June transits within the 8
year periodicity folowed by 2 December transits -
1631 and 1639 were December transits.
1761 and 1769 were June transits
1874 and 1882 were December transits
2004 and 2012 will be June transits
and so on. - Rathnasree
Rathna, I do not know the series for the Mercury transits but it does make
sense they being 180 degrees apart from each other. That's where the
ascending and descending nodes are located.
Also...just by shear coincidence of course...the total years for a
complete cycle of (8, 121.5, 8, 105.5) is 243 years and one Venus day
is 243 days and 243 days is 2/3 of an Earth year.
Did you know that every 5 Earth years Venus orbits the Sun "8" times.
This is getting to be fun stuff !!!
Clive
Clive, Mercury Transit frequencies - these have been the dates for recent
transits -
12 November 1907
7 November 1914
7 May 1924
10 November 1927
11 May 1937
12 November 1940
14 November 1953
5 May 1957
6 November 1960
9 May 1970
10 November 1973
12 November 1986
6 November 1993
15 November 1999
7 May 2003
8 November 2006
One can see that the November node crossing frequency is higher than the May
ones. - Rathnasree
About the November and May Mercury Transits and the higher frequency
of the November ones - this is what Fred Espenak says in the NASA
GSFC site devoted to transits -
---During November transits, Mercury is near perihelion and exhibits
a disk only 10 arc-seconds in diameter. By comparison, the planet is
near aphelion during May transits and appears 12 arc-seconds across.
However, the probability of a May transit is smaller by a factor of
almost two. Mercury's slower orbital motion at aphelion makes it less
likely to cross the node during the critical period.---
I am not fully comfortable with this logic yet, as it seems a little
contrary to the usual Astrophysical argument that if some phase space
is covered faster by a body - the frequency of occurence in that
phase space would be smaller - but, I am sure, I am missing
something, in my argument.
We did discuss this issue of the Mercury Transit frequencies in May
and November, over at the Nehru Planetarium group, last May.
Rathnasree
One year of venus is 224.7 earth days, meaning that Venus completes one
circle
around the Sun and comes back at the place from from where it started.
However, In these 224.7 earth has moved ahead in its own orbit is much behind
Venus. So Venus starts another round the Sun and after some time it catches with
the Earth.
Thus, If you draw an imaginary line connecting Earth and Sun, Venus crosses that
line after every 584 days, or about 1 year, 7 months.
This, 584 days is called the Synodic Period, or the Cycle of Venus, the period
between Inferior Conjunctions. In this time, the Earth completes 1 7/12 orbits,
but Venus completes 2 7/12 orbits.
Now, Ecliptic is the path on which the Sun appears to travel on the sky of
earth. Earth's orbit has 0 degree inclination on this ecliptic. Venus' orbit is
tilted about 3.39 degree from this orbit. Hence most of time venus comes
straight between the Earth and the Sun, it is not exactly in the straight line
connecting earth and sun. It is either above or below this line due to that
inclination of its orbit. Thus, Transit does not take place every time Venus
comes between Earth and Sun.
considering a 365 day year and 30 day month of earth,
584 days x 1 = 584 = 1 year 7 months 10 days of earth
584 days x 2 = 1168 = 3 year 2 months 13 days
584 days x 3 = 1752 = 4 year 9 months 22 days
584 days x 4 = 2336 = 6 year 4 months 26 days
584 days x 5 = 2920 = appx 8 years
Thus, Five cycles of venus correspond very close to about 8 years (adjust for
leap yaers and 27/29/31 day months) of earth. Their paths come in such a line
when the
inclination of Venus' orbit is near zero, so a transit occurs,
Similar explanation can be given for 121.5 and 105.5 year gaps between
successive transits.
The last 5 inferior conjunction were on these dates.
June 10, 1996
January 16, 1998.
August 20, 1999
March 30, 2001
October 31, 2002
next one: June 8, 2004
Taking in account non-30 day months and leap day, there is about 2 or 3 day
shortfall in 8 earth years and five venus cycles, thus you will find that venus
inferiour conjunction (and thereby transits) fall two days before the previous
transit on 8 year gap.
next to the above: June 6, 2012. when a transit will occur
next transit after the above will be after 105.5 years (after 2012), on December
13, 2117.
=============
past transits:
Telescopes were invented by Galileo on 1610. Only after that the passage of tiny
mercury/ venus on
the disc of sun became possible.
7 dec 1631
4 dec 1639
6 jun 1761
3 jun 1769
9 dec 1874
6 dec 1882
this 2004 transit will be 7th venus transit that human beings have viewed.
-Rawat
Over the years, I have realized there being several "oddities"
relating to the planet Venus. The most common being the retrograde
motion and one complete day on Venus equaling exactly 2/3 of an Earth
year.
This relates to...every "2" complete "rotations" of the
"2nd" planet
from the Sun, the "3rd" planet will "orbit" "3"
times.
Venus and Earth share another "unique" feature. They align every 2.6
orbits of Venus (1.6 orbits of Earth). This means that every 8 years
Venus and Earth realign in the same location on their orbital paths.
We know that 13 is said to be unlucky...well that's how many times
Venus orbits in those 8 Earth years. See
<http://amitron2001.tripod.com/cgi-bin/Aztec_calendar.htm>
Next year we will observe Venus as it transits the Sun, similar to
our recent witnessing of Mercury.
The average orbital distance of Venus from the Sun is 108.2 Mkl
compared to 57.9 Mkl for the smaller planet Mercury.
What struck me as being odd is their ratio of distance...it is 1.87:1.
The "physical" size ratio of Earth to Mars is the identical ratio!
Clive
Compiled from the VenusTransit group