Originally posted by Anonymous ATS
Retrograde motion is the apparent looping movement of a planet in it's orbit of the Sun.
Planets with a superior orbit to Earth's make that
apparent looping or wandering motion but this is not the case for inferior planetary orbits like Venus'.
Venus appears as the evening star after sunset rising to about 47 degrees above the horizon and getting brighter as it moves closer to Earth. Then it
starts to appear lower in the sky every night until it sinks below the horizon with the setting sun and passes Earth to become the morning star on its
way back around the Sun again. The retrograde motion referred to in this thread is Venus' sidereal rotation (axial spin) which is in a clockwise
(Retrograde) motion.
The surface of Venus cannot be seen from Earth due to its thick cloud cover and I find it curious that even though Venus does not have a magnetic
field protecting its atmosphere it is 90 times more dense then Earth's.
Venus does not possess an intrinsic magnetic field to protect its
atmosphere from the solar wind...In particular, the interaction causes Venus’s atmosphere to lose its gases in the form of ionized particles...They
are predominantly hydrogen, oxygen and helium ions...ASPERA finally established the composition of the escaping plasma and measured that the escape of
hydrogen to oxygen is, indeed, in the same ratio as water.
Source-ESA So
what happened to Venus' magnetic field? Did it ever have one and if not then why is the atmosphere 90 times more dense then Earth's? The effects of
the solar wind on Venus' atmosphere over 4.5 billion years should have stripped it away by now.
Venus orbits the sun in 224.7 days in a prograde motion (CCW) and radar mapping has determined that its sidereal rotation is 243.018 days (+/-0.18) in
a retrograde motion (clockwise).
The synodic alignments of Venus with Earth, called inferior conjunctions, occur every 584 days and what's interesting is at these alignments the same
side of Venus faces Earth.
Java Applet of Venus Resonance (if the Applet runs fast hit the medium
or slow tab)
There is also an 8:13 near orbital resonance with Earth every 5 inferior conjunctions, they are not commensurate as they are off by 2.44 days in 8
Earth years. Orbital information sources from-
NASA's Planetary fact sheet
and-
Allen's Astrophysical
Quantities.
Venus makes a pentagram
When you mark these 5 synodic alignments in order of their occurrences (1-5) on a circle representing Earth's orbit and you connect them in numerical
order a five point star is made (Pentagram).
Here is a screen shot I took from Celestia showing the 5 synodic periods starting with (1) June 8 2004. The yellow dots represent Earth with the
synodic dates, green dots are Venus, and the two circles next to the starting point (1) show the synodic period for June 6, 2012- 2.44 days early.
This is an approximate representation.
This synodic pentagram has been pointed out in a previous thread by ViolatorR titled,
"The
Secret Lives of Venus,"
but replies dismissed this as arbitrary alignments. I want to make it clear that the synodic periods of Venus are measured from the same specific
point, closest approach, and the results have to do with the orbital mechanics of planetary alignments and are in no way arbitrary. Venus is the only
planet that makes this pattern and the fact that it migrates clockwise 2.44 days every 8 years makes for an interesting cyclical pattern.
[edit on 2/19/2009 by Devino]