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On June 5 2012, SDO collected images of the rarest predictable solar event—the transit of Venus across the face of the sun. This event lasted approximately 6 hours and happens in pairs eight years apart, which are separated from each other by 105 or 121 years. The last transit was in 2004 and the next will not happen until 2117.
The videos and images displayed here are constructed from several wavelengths of extreme ultraviolet light and a portion of the visible spectrum. The red colored sun is the 304 ångström ultraviolet, the golden colored sun is 171 ångström, the magenta sun is 1700 ångström, and the orange sun is filtered visible light. 304 and 171 show the atmosphere of the sun, which does not appear in the visible part of the spectrum.
With coronagraphs, the Sun is being blocked by an occulting disk, seen here in blue, so that SOHO can observe the much fainter features in the Sun's corona. The actual size of the Sun is represented by the white disk.
The transit of Venus begins tomorrow, June 5, at about 6pm Eastern Daylight Time, or about 10pm Universal Time. It will last approximately 6 hours.
These are the basic images, collected from the telemetry. To see the insets composited, see Venus Transit 2012 Composited Visuals.
Some artifacts may be visible from the compositing, but you have to look pretty closely to see them.
The color table threshold was raised for these images, reducing the amount of noise visible in the images.
Note: There is an interesting artifact worthy of mention and clarification, and that is as Venus crosses the solar limb, the limb appears to be visible through the planet in some of the imagers (most notably the ultraviolet channels). Discussion with the scientists who built the imagers suggest this might be 'crosstalk' between the readouts of the four CCD panels that make up a complete image. It is an artifact of the imaging system.
A transit is when a planet passes directly between the Sun and the Earth and we see the planet as a small dot moving slowly across the face of the Sun. A Venus transit occurred in 2004 (see Venus Transit from GOES/SXI). Prior to that it was 1882. The last Venus transit occurred on June 5-6, 2012 and the next one won't occur until 2117 (See the NASA Eclipse Web Site).
To understand the significance of these events, it helps to know the history of how the Venus transits provided one of the first estimates of the size of the Solar System, and eventually the Universe (see A Brief History of the Transit of Venus).
In this visualization, there are a few things which should be noted.
1) The camera view is NOT from anywhere on the surface of the Earth, but corresponds to an observer positioned along the Earth-Sun line, but over the north pole of the Earth. This causes the path of Venus to cross the solar disk lower (closer to the solar equator) than it would appear to an observer on the surface of the Earth.
2) The ephemeris used for computing the planetary positions was not the high-precision JPL ephemeris (DE-421), but a lower-precision approximation. Yet, when tracked in detail, the transit takes place only about five hours later. It was decided that since the view of the transit in this visual does not correspond to any actual location ON the Earth, it might be misleading to present high-precision timing of the event.
This visualization was developed for conceptual illustration and not meant for precision scientific use.