On Tuesday, the planet Venus crossed in front of the sun in a slow manner, marking the final visible transit from Earth for the next 105 years. Transits of Venus occur in pairs, spaced eight years apart, with over a century between cycles. During this recent transit, Venus appeared as a small black dot moving slowly across the sun's northern hemisphere. Many people watched the six-hour and 40-minute event online through various websites offering live video feeds from different locations around the world. The Prescott Observatory in Arizona provided close-up views of the transit, showing a potential solar flare forming just below the sphere of Venus. Tuesday's transit, which marked the completion of a pair of transits that occurred in 2004 and 2012, started at 6:09 p.m. EDT (2209 GMT). Observers on all seven continents, including Antarctica, had the opportunity to witness at least some portion of the transit. Even astronauts on the International Space Station were able to view the event. Space station flight engineer Don Pettit expressed his excitement about the transit, stating that he had been preparing for it and brought a solar filter specifically for the occasion. The focus is not solely on beautiful images. Various scientific experiments were organized, including research that could aid in the discovery of habitable planets outside of our solar system. Telescopes like NASA's Kepler space telescope are currently being utilized to locate extrasolar planets that transit in front of their host stars, similar to Venus passing in front of the sun. Scientists planned to study Venus's thick atmosphere during its transit to develop methods for studying atmospheres of other planets. Analyzing Venus's atmosphere could also provide insights into the differences between Earth and Venus, despite their similar size and distance from the sun. Venus has a very thick atmosphere, 100 times denser than Earth's, composed mainly of carbon dioxide, a greenhouse gas. The planet's surface temperature reaches a scorching 900 degrees Fahrenheit (480 degrees Celsius), with fast-moving clouds of sulfuric acid causing acid rain at speeds of 220 miles per hour. Despite being known as the goddess of love, Venus is not a planet one would want to get too close to, according to an astronomer on Slooh.com. Scientists are studying Venus' climate to gain insight into potential changes in Earth's atmosphere. In past transits of Venus, scientists determined the size of the solar system and the distance between the sun and planets. The upcoming transit on Tuesday will be the eighth since the telescope was invented, and the last until December 10-11, 2117. This transit will be the first to occur with a spacecraft at Venus, with observations from Europe's Venus Express probe being compared to those made by various telescopes, including NASA's Solar Dynamics Observatory, the joint US-European Solar and Heliospheric Observatory, and Japan's Hinode spacecraft.