Today sky-watchers around the world will be able to witness a transit of Venus—a rare event that won’t be seen again for more than a century.
The transit will give astronomers a chance to study the atmosphere of Venus as well as to tweak models for searching for planets around other stars, reports National Geographic.
The Venus transit will last for nearly seven hours and will look like the sun is being punctured by a small black dot, according to The Huff Post.
“Venus’s diameter will appear only about a 30th the diameter of the sun, so it will be … like a pea in front of a watermelon,” said Jay Pasachoff, an astronomer at Williams College in Massachusetts.
“The effect won’t be visually impressive, but that black dot against the sun is a remarkable thing to see,” he added.
The transit of Venus will be visible from Hawaii, Alaska, the Philippines, New Zealand, Japan ,most of Australia, and parts of eastern Asia. Countries in the Western Hemisphere will see the transit on Tuesday, while those in the Eastern Hemisphere will see it on Wednesday.
According to NASA sky-watchers from all over the world except for western Africa, southeastern South America, Portugal and parts of Spain will be able to watch this once-in-a-lifetime event.
This phenomenon occurs when Venus crosses between the Sun and the Earth. The last transit took place in 2004, and we won’t see another until 2117.
Only two planets – Mercury and Venus – which are closer to the sun than our planet, can undergo this unusual alignment.
However, Mercury with its relatively tight orbit, circles the sun fast enough that we see the innermost planet transit every 13 to 14 years.
But transits of Venus are extremely rare, due to that world’s tilted orbit: After the 2012 Venus transit, we won’t see another until 2117.
“This is a once-in-a-lifetime event because it won’t happen again for another 105 years or so…. I’m pretty lucky to be alive right now,” Chris Spellman, 40, of Monrovia, said LA Times while setting up his telescope at the Griffith Observatory.
The Griffith Observatory in Los Angeles was expecting thousands of people to show up on its lawn to view the cosmic show, and experienced astronomers united with amateurs to watch something that has not been viewable in California since 1882.
“We’re just amateurs. We just came to see the event. It seemed pretty cool,” said Nathan Smith, 28, of Burbank.
Astronomers first observed a transit of Venus with telescopes in 1639.
But it wasn’t until 1769 that dozens of scientists scattered across the globe in order to make detailed measurements of the event.
This year the transit of Venus will be visible even to the naked eye, but it is never safe to look at the Sun without the proper eye protection.
Observers should always use special “eclipse glasses” or telescopes equipped with solar filters.
It is possible also to make a pinhole camera to watch the transit of Venus safely. For that it is necessary to cut a hole about a quarter-inch (0.6-centimeter) wide in a piece of cardboard paper, and use the hole to project an image of the sun onto a flat surface, such as a wall or sidewalk.