Don't Miss June's Rare Transit of Venus
 |
| The rare transit of Venus across the face of the Sun in 2004 was one of the better-photographed events in sky history. The dark round circle on the right side of the sun is Venus crossing in front of the Sun.
(Image Credit: David Cortner , davidcortner.com/astro/vtransit)
|
What is Transit?
Transit is an astronomical event that occurs when one celestial body appears to move across the face of another celestial body, hiding a small part of it, as seen by an observer at some particular vantage point. If the first celestial body hides a major part, or all of, the second celestial body, then it is an occultation rather than a transit.
Transit of Venus:
Transit of Venus across the Sun takes place when the planet Venus passes directly between the Sun and Earth, becoming visible against (and hence obscuring a small portion of) the solar disk. During a transit, Venus can be seen from Earth as a small black disk moving across the face of the Sun. A transit is similar to a solar eclipse by the Moon. While the diameter of Venus is almost four times that of the Moon, Venus appears smaller, and travels more slowly across the face of the Sun, because it is much farther away from Earth.
Frequency of Transit of Venus:
The earth orbits the Sun in 365.25 days and Venus takes 224.7 days. After every 584 days Venus comes in between the Sun and Earth, therefore we should be able to see Transit of Venus after every 19 months. But at every conjunction the Earth, Venus and the Sun are not exactly along a straight line since the orbit of Venus is inclined by 3.4 degrees to the orbital plane of Earth. Transit can happen only when the conjunction occurs at the nodes where orbital planes intersect. These transits are observed in June and December as the only condition for a transit to occur is at nodes.
Transits of Venus occur in a pair separated by 8 years. A pair of transits separated by 8 years repeats at intervals of 121.5 years and 105.5 years alternatively.
On the 5/6th of June 2012, the planet Venus will transit the Sun and will be the last Venus transit of this century. Previous transit took place on June 8, 2008. After 2012, the next transits of Venus will be in December 2117 and December 2125 i.e. after 105 years. We will have to wait for 105 years for next transit, so not to miss this last transit of Venus in our lifetimes.
Visibility of Transit of Venus:
Transit of Venus will be visible from most of the world. Let's see the map below. From the western Pacific, eastern Asia and eastern Australia the entire transit is visible. Beginning of the transit will be visible from most of the North and Central America, and northern South America on June 5th but the Sun will set before the event ends. And observers in Europe, western and central Asia, eastern Africa and western Australia will be able to observe the event immediately after Sunrise on June 6th (when the transit is already in the middle).
 |
| (Image Credit: http://eclipse.gsfc.nasa.gov/OH/transit12.html ) |
Observation of Transit & Safety:
1.Projection of the Sun using Telescope or Binoculars:
 |
| Please Note: Make sure that you don't look at the Sun through a telescope or binocular while adjusting the projected image on paper. |
Transit can be viewed through solar filters which are scientifically tested. Buy these solar filters from official sources.
Black Drop Effect:
 |
| Black Drop Effect |
The black drop effect is an optical phenomenon visible during a transit of Venus. When the disc of Venus is moving inside the disc of the Sun, called internal ingress, and when the disc of Venus is just about to leave the Sun, called internal egress, an interesting phenomenon called black drop effect occurs. A small black teardrop appears to connect the Venus' disk to the limb of the Sun, making it difficult to note the exact timing of ingress and egress.
Initially, the black drop effect was thought to be caused by the presence of the atmosphere of Venus, however when a similar black drop effect was also observed during transit of Mercury, which doesn't have an atmosphere, led to the inference that a transiting planet's atmosphere cannot be the cause of black drop. Turbulence in the atmosphere of the Earth can also contribute to the black drop effect. But the black drop effect was observed from outside the Earth's atmosphere during the 1999 and 2003 transit of Mercury by TRACE satellite. So above reasoning may not be true.
 |
| Edmund Halley, who later had a comet named after him, showed how the Venus Transit could be used to calculate the distance between the Earth and the Sun. He knew he would not live until the next transit, in 1761, but urged scientists to embark on worldwide expeditions to undertake the measurement. (Image Credit: American Philosophical Society Collection) |
 |
| Transit of Venus from Flagler Beach in Florida: June 2004 (Image Credit: AP Photo | Daytona Beach News-Journal, Jim Tiller) |
Amazing Transit Facts:
As seen from Earth, only transits of Mercury and Venus are possible. The simultaneous occurrence of a transit of Mercury and a transit of Venus is possible, but it's very rare. Such an event last occurred on 22 September 373,173 BC and will next occur on 26 July 69,163, and again on 29 March 224,508.
The simultaneous occurrence of a solar eclipse and a transit of Venus is also possible. On 1 November 15,607 BC, a solar eclipse occurred during a transit of Venus. The next solar eclipse occurring during a transit of Venus will be on 5 April 15,232.
This is a last transit of Venus in our lifetimes, so start preparing for the transit. Very few days are left. And don't forget to share your experience of transit observation. :)
“We are just an advanced breed of monkeys on a minor planet of a very average star. But we can understand the universe. That makes us something very special.” - Stephen W. Hawking
Good to see such informative article.
ReplyDelete