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RE: The transit of Venus
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Transits are similar in concept to an eclipse of the Sun, when the Moon passes in front of it, Except that it is when one of the two planets closer to the Sun than the Earth, i.e. Mercury or Venus, passes in front of the disc of the Sun. Transits of Venus are very rare. Only six such events have occurred since the invention of the telescope (1631, 1639, 1761, 1769, 1874 and 1882).
They occur in pairs, separated by 8 years between each of the pair, every 121.5 years. One pair occurs either about 7 June, or about 8 December. There is a separation of 243 years between pairs occurring on the same date. The last pair of transits of Venus occurred in December 1874 and December 1882. This is due to the Earth/Venus gravitational resonance.

Geocentric

Dynamical Time

Position Angle
Transit seen from Aberdeen

Eclipse begins

05:14:34

116.3

Umbra eclipse begins

05:34:00

119.4

Maximum eclipse

08:20:49

Umbra eclipse ends

11:07:38

213.2

Eclipse ends

11:27:04

216.3



08 JUNE 2004 The entire transit is visible from Europe, Africa (except western parts),the Middle East, and most of Asia (except eastern parts). The transit is still in progress as the sunsets from Australia, Indonesia, Japan, Philippines, Korea, easternmost China and Southeast Asia. Likewise, the transit is already in progress at Sun rises with for observers in western Africa, eastern North America, the Caribbean and most of South America. Venus will cross at a solar latitude of about -60 degrees then cross the southern hemisphere.

455278846_0a3ec62755.jpg

The Sun will rise at 04:05 GMT. The transit will start at about 05:21 GMT, when the altitude of the dawn Sun will be 9 degrees. Venus will take 20 minutes to cross the limb of the Sun Mid-transit will be at 08:23 GMT. Venus will again take 20 minutes to cross the limb of Sun, and the transit will end at 11:16 GMT, when the altitude of Sun will be 61 degrees. The time taken for the entire transit will be 6 hours. The Sun's coordinates will be: RA 05h 07m, Dec +22deg 53min.
The apparent angular diameter of Venus will be 58".6 arc-seconds , about 3% of the Sun's 1887" arc-seconds diameter.

455278824_42b1fc8a12.jpg

The December 6, 1882, transit of Venus was already under way when the Sun rose over Lick Observatory in California and David Peck Todd began photographing the planet's march across the solar disk.
Edmund Halley was the first to realise using Kepler's third law that transits could be used to measure the Sun's distance. Cook`s expeditions to the southern seas in 1761 and 1769 gave astronomers values for the Sun's distance. The planet Mercury can also transits the Sun. Since Mercury orbits the Sun faster, it undergoes transits much more frequently. There are either 13 or 14 transits of Mercury every century. All Mercury transits fall within several days of 8 May and 10 November. The next two transits of Mercury are on 2003 May 07 and 2006 Nov 08.

The next transit of Venus will occur on 2012 June 06. This transit will be visible from the Pacific, Australasian and Eastern Asia. During the next six hours 10 minutes , Venus gradually traverses the Northern Hemisphere , at solar latitude of about +45 degrees, of the solar disk; at a relative angular rate of approximately 4 arc-min/hr. Mid-transit will be at 01:28. At contact III, the planet reaches the opposite limb (known as egress, contacts I and II define the phase called ingress). The transit ends at contact IV, at about 04:54 GMT.
By the way, the next pair of Venus transits occurs over a century from now on 2117 Dec 11 and 2125 Dec 08.

455278820_daed4502fc.jpg


(8 June, 2004)
The planet Venus has completed a very rare passage across the face of the Sun - an event not witnessed since 1882.
The so-called transit of Venus began at about 06:20 BST (05:20 GMT) with the planet's tiny black disc edging over the bright limb of our star.
The phenomenon continued for about six hours, ending around 12:24 BST.

Source



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L

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Like occultations, there is another class of celestial phenomena that hold attraction to the astronomer. Known as 'transit' it represents the passage of a planet across the solar disc.
Viewing from the earth there are only two planets that can come in between the Sun and ourselves: Mercury and Venus. The others move in orbits that lie outside ours, around the Sun and so we never can see them transit across the solar disc.

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