About the transit of Venus . . . . Discover it

T r a n s i t o f Venus

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8th June 2004, 6th June 2012

About Transit of Venus

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What is Transit of
Venus?

When does it occur?

Why is it rare?

Why is it important?

1. What is transit of Venus?

The orbit of Venus lies within that of the Earth, and being inclined at a small angle to the ecliptic, it sometimes happens that the planet comes directly between the Earth and the Sun; it is then seen as a dark spot moving across the Sun's disc. Such an occurrence is called transit of Venus

2. When does it occur?

The transits occur at irregular and distant intervals which are alternately short and long; the short ones are always 8 years, the long ones alternately 121 ½ and 105 ½ years. Only five transits have yet been seen; those of 1639, 1761, 1769, 1874 and 1882.

The following table list of all transits of Venus during the 600 years from 1601 through 2200.
Transit of Venus: 1601 - 2200

Date                    Universal Time            Separation               Intervals
                                                               (Sun and Venus)        (in yrs)
1631 Dec 07         05:19                            040"                          -
1639 Dec 04         18:25                            522"                         8
1761 Jun 06         05:19                            573"                         121 ½
1769 Jun 03         22:25                            609"                         8
1071 Dec 09         01:05                           032"                         105 ½
1882 Dec 06         17:06                            634"                         8
2004 Jun 08        08:19                            627"                         121 ½
2012 Jun 06         01:28                            553"                         8
2117 Dec 11         02:48                           724"                         105 ½
2125 Dec 08         16:01                            733"                         8
2247 Jun 11        11:30                            693"                         121 ½

3. Why is it Rare?

If the orbit of Venus were in the same plane as that of the Earth, or very nearly so, we should see Venus crossing the disc of the Sun at every inferior conjunction; but in actual fact the two orbits are inclined or tilted relative to one another to such an extent that Venus nearly always passes to the north or to the south of the Sun.
Transits of Venus are only possible during early December and early June when Venus's orbital nodes pass across the Sun. If Venus reaches inferior conjunction at this time, a transit will occur. Transits show a clear pattern of recurrence at intervals of 8, 121, 5 8, and 105.5 years. The next pair of Venus transits occur over a century from now on 2117 Dec and 2125 Dec 08.

4. Why is it Important?

A transit of Venus is very rare. Transits have been used to find the Sun's distance. The fundamental aim of the transit expeditions was to enable the mean Earth-Sun distance, used as the astronomical unit (AU), to be determined.

5. for more information: Slides presentation by Dr T. V. Venkateswaran