Tuesday, 29 May 2012

The Transit of Venus June 6, 2012, over the Disc of the Sun


A Transit of Venus over the disc of the Sun will occur in the morning of Wednesday June 6, 2012 AD. This transit phenomenon will be visible fromIndia.

       The transit of Venus is a phenomenon when the Venus will be seen as a black spot traveling from one limb of the solar disc to the other. From the Earth this phenomenon is seen when the Venus passes between the Sun and Earth and the planet gets aligned with the Sun. This is an extremely rare event, occurs in pair with a gap of 8 years, at intervals of 8, 121½, 8, 105½ and 8 years. The Venus appears as a dot on the solar disc because its angular size is very small compared to that of the Sun as seen from the Earth.

       The transit of Venus begins with contact-I, the instant when the disc of the planet Venus is externally tangent with the Sun (Ingress exterior) followed by contact II when the Venus is internally tangent with the Sun (Ingress interior). The Venus will be seen as a black spot, travelling several hours over the face of the disc, will reach the opposite limb of the Sun at contact III, when the disc of the planet Venus is internally tangent with the Sun (Egress interior). Finally the transit ends at contact-IV when the disc of the planet Venus is externally tangent with the Sun (Egress exterior).

General Visibility
      The entire transit event (all four contacts) will be visible from north western North America, the western Pacific, northern Asia, JapanKorea, eastern ChinaPhilippines, eastern Australia and New Zeeland. The beginning of the transit when the Sun sets while the transit is inprogress, will be seen from most the North America and north west South America. Similarly observer in ntral Asia, the Middle East, Europe and eastern Africawill see the end of the event since the transit will already be in progress at sunrise from those locations.

Visibility in India
    The beginning of the event comprising of Ingress exterior (Contact I) and Ingress interior
     (Contact II) will not be visible from any place in India as the event will be in progress before    sunrise. The observers in India will see the event after sunrise for a duration varying from about 5 hours 30 minutes for the observers located in the east of the country to about 4 hours 30 minutes for the observers located in the west of the country.

      The last transit of Venus occurred on June 8, 2004 when the entire event was visible from all parts of India. The next pair of transit of Venus will occur after a century on Dec 11, 2117 and Dec 8, 2125.

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