Rare transit of Venus on June 6

Sri Lankans will have a chance to witness one of the rarest celestial phenomena known as “Venus Transit” with the sunrise on June 6. Millions around the world will witness this rare astronomical phenomenon. Such an event occurs when the planet Venus passes almost exactly between the Earth and the Sun, which is incredibly rare.

It is kind of an eclipse. During the transit, Venus appears as a small black disc moving across the sun, usually taking nearly seven hours. Since first predicted by the German mathematician and astronomer Johannes Kepler in the 17th Century, only six Transits of Venus have been observed.

Transits of Venus first gained worldwide attention in the 18th century as it gave us a way to find the distance between Earth and Sun - the exact value of astronomical unit. Transits of Venus occur at regular intervals that repeat over a 243-year period. Intervals between successive transits are eight years, 105.5 years, eight years, and 120.5 years.

The last transit in the current cycle was in June 2004, but before that the last transit was in December 1874 and December 1882. The next transit after this one will be in December 2117 and December 2125 - so this is the last chance to see a transit of Venus in our lifetimes! The passage of Venus in front of the Sun on June 6 will be visible in its entirety in the Arctic areas as well as in eastern parts of Asia and Australia.

However, Sri Lankans can see only the latter part of it for the transit begins around 3.39 a.m. Sri Lanka standard time, before sunrise. The Venus transit will be visible to Sri Lanka from about 6.00 a.m. on June 6 with sunrise, greatest of transit at 7.03 a.m. and the transit ends at 10.22 a.m. Observing the transit will not require a telescope; the disc of Venus is large enough to be seen with the unaided eye as the glare of the Sun is less in the early hours of the morning. However, extreme precaution must be taken when observing the event or permanent eye damage and/or blindness will occur.

Therefore the Venus transit should not to be observed with the naked eye. The same protections should be used as during solar eclipses said Prof Chandana Jayarante, Professor in Physics, University of Colombo and Consultant to the Space Science Division, Arthur C Clarke Institute for Modern Technologies. One can use some type of projection technique or a solar filter. A no. 14 welder’s glass is a good choice.

Do not use sun glasses or tinted glasses as many of them cannot filter out the infrared radiation from the sun. If the weather permits, this event can also be watched through the internet through live webcasts planned from Arthur C Clarke Institute Venus transit observational camp in Trincomalee (www.accimt.ac.lk) and /or simultaneous live webcasts made by University of Colombo Astronomical Society (www.uocmas.info) from Venus transit observation camps in Trincomalee and Colombo University playground Prof. Jayaratne said.