Starship Asterisk*

markc wrote:I had the same question about the rare eclipse event. Does that mean that Earth and Venus orbits are not exactly in the same plane?

http://en.wikipedia.org/wiki/Transit_of_Venus wrote:

[b][color=#0000FF][size=150]Diagram of transits of Venus and the angle between the orbital planes of Venus and Earth[/size][/color][/b]

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<<Venus, with an orbit inclined by 3.4° relative to the Earth's, usually appears to pass under (or over) the Sun at inferior conjunction. A transit occurs when Venus reaches conjunction with the Sun at or near one of its nodes—the longitude where Venus passes through the Earth's orbital plane (the ecliptic)—and appears to pass directly across the Sun. Although the inclination between these two orbital planes is only 3.4°, Venus can be as far as 9.6° from the Sun when viewed from the Earth at inferior conjunction. Since the angular diameter of the Sun is about half a degree, Venus may appear to pass above or below the Sun by more than 18 solar diameters during an ordinary conjunction.

Sequences of transits usually repeat every 243 years. After this period of time Venus and Earth have returned to very nearly the same point in their respective orbits. During the Earth's 243 sidereal orbital periods, which total 88757.3 days, Venus completes 395 sidereal orbital periods of 224.701 days each, equal to 88756.9 Earth days. This period of time corresponds to 152 synodic periods of Venus.

The pattern of 105.5, 8, 121.5 and 8 years is not the only pattern that is possible within the 243-year cycle, because of the slight mismatch between the times when the Earth and Venus arrive at the point of conjunction. Prior to 1518, the pattern of transits was 8, 113.5 and 121.5 years, and the eight inter-transit gaps before the 546 CE transit were 121.5 years apart. The current pattern will continue until 2846, when it will be replaced by a pattern of 105.5, 129.5 and 8 years. Thus, the 243-year cycle is relatively stable, but the number of transits and their timing within the cycle will vary over time. Since the 243:395 Earth:Venus commensurability is only approximate, there are different sequences of transits occurring 243 years apart, each extending for several thousand years, which are eventually replaced by other sequences. For instance, there is a series which ended in 541 BCE, and the series which includes 2117 only started in 1631 AD.>>

ellishw wrote:
So why is there no mention (that I can find) of "Transit of Venus?"
Isn't a "transit" historically a significant event?
Here it is referred to as an "eclipse" but is that not the same thing?

• Something that even you have never seen.
  Letters of transit signed by General de Gaulle.
  Cannot be rescinded. Not even questioned.
  Tonight I'll be selling those for more money than I ever dreamed of.
  And then, adios, Casablanca.

http://en.wikipedia.org/wiki/Eclipse wrote:
<<An eclipse is an astronomical event that occurs when an astronomical object is temporarily obscured, either by passing into the shadow of another body or by having another body pass between it and the viewer. An eclipse is a type of syzygy. The word "transit" refers to cases where the nearer object appears considerably smaller than the more distant object. Cases where the nearer object appears larger and completely hides the more distant object are known as occultations.

A syzygy (from the Ancient Greek suzugos (σύζυγος) meaning, “yoked together”.) is a straight-line configuration of three celestial bodies in a gravitational system. Solar and lunar eclipses occur at times of syzygy, as do transits and occultations. The term is often applied when the Sun and Moon are in conjunction (new moon) or opposition (full moon).

Eclipse is derived from the ancient Greek noun ἔκλειψις (ékleipsis), which means "the abandonment", "the downfall", or "the darkening of a heavenly body", which is derived from the verb ἐκλείπω (ekleípō) which means "to abandon", "to darken", or "to cease to exist," a combination of prefix ἐκ- (ek-), from preposition ἐκ (ek), "out," and of verb λείπω (leípō), "to be absent". The term eclipse is most often used to describe either a solar eclipse, when the Moon's shadow crosses the Earth's surface, or a lunar eclipse, when the Moon moves into the Earth's shadow. However, it can also refer to a planet moving into the shadow cast by one of its moons, a moon passing into the shadow cast by its host planet, or a moon passing into the shadow of another moon. A binary star system can also produce eclipses if the plane of the orbit of its constituent stars intersects the observer's position.>>

Psnarf wrote:
It is so convenient having a star close enough to study in such detail.

neufer wrote:

Psnarf wrote:
It is so convenient having a star close enough to study in such detail.

There was another good reason as well but it skips my mind for the moment.

Boomer12k wrote:Whoa.....now I know where "Paisley" comes from in the sixties.....Psychedelic. Wow...Flashback....Trippin'.....Far Out....Out of Sight, Man....

:---[===] *

Psnarf wrote:It is so convenient having a star close enough to study in such detail. Magnetic coronal loops, a coronal hole so close you can peek inside (using a satellite from a safe distance), can't see that stuff on other stars. It staggers my imagination to know that the loops are only visible in the ultraviolet frequencies. Multiply ionized iron at two million degrees Kelvin formed by the fusion of silicon?
http://www.flickr.com/photos/pldove/716 ... otostream/
I've read that the layers of elements from fusion just before supernovae starts with iron at the center from silicon fusion, silicon from magnesium fusion, magnesium from neon fusion, neon from oxygen fusion, oxygen from carbon fusion which is from helium fusion, with hydrogen at the outermost layer. I did not know that there was iron near the surface, thought the magnetic lines of force were generated from the motion of electrons. The presence of iron suggests there is Si, Mg, Ne, O, and C in there somewhere, unless it is the product of fission reactions. I learn a lot at apod.com, particularly how vast there is yet to learn.

Star Geezer wrote:Why is Venus not on the 9:00 -3:00 horizontal axis in the photograph?
In other words, on the ecliptic plane.

JohnD wrote:
But my memory is that the globe of Venus was much smaller on the Sun than appears in this image. A quick search for "Transit of Venus" images confirms this. But is this an illusion of the large image shown in this APOD?

cindy4444 wrote:
I enjoyed seeing it and sorry no one alive now will have the chance again. In connection with viewing it, I did a lot of studying of the orbits and planes for Earth and Venus' orbit. Interesting that they cross in the same plane only in June and December and precession has not changed this in centuries?