Unless you were born yesterday you’re probably never going to see another transit of Venus. Only seven of them have ever been observed and the next one is in 2117.
So here are some beautiful images to celebrate the moment a decade ago today when, on June 5, 2012 it was possible to see the second rock from the Sun pass in front of it as seen from the third rock from the Sun.
A transit of Venus across the Sun takes place when the planet Venus passes directly between the Sun and Earth. It can be seen as a small black dot moving across the face of the Sun. During the transit Venus had an apparent diameter of almost 58 arcseconds, which is about 3% of the Sun’s apparent diameter.
A transit of Venus happens twice in eight years then not at all for 105 years. The last time it happened was on June 5/6, 2012 and the next time it will happen will be December 10/11, 2117. It will be followed by another on December 8. 2125.
Given that it’s only observable from the day-side of the planet, a transit of Venus therefore can be a once or even twice in a lifetime event. Or it can happen exactly zero times in a person’s lifetime.
So the 2012 transit of Venus was a massive event for an entire generation of sky-watchers and nature-lovers, particularly those that missed out on the 2004 event. Crowds gathered at observatories across the world, solar filters in hand, hoping for a glimpse of the majestic event.
It was largely a Pacific event, visible across New Zealand, Japan and large parts of Australia and East Asia as well as in the northwesternmost parts of North America. IT was also glimpsed in the morning in Europe.
Some of the best views were from above the clouds on one of the world’s largest volcanoes. “I went to Mauna Kea in Hawaii because it was one of the best places to see the entire transit, which was centred over the Pacific Ocean,” said Tom Kerss, astronomer and author of The Squirrel that Watched the Stars. “About 300 to 400 people were gathering at the Visitor Center, which is 9,500 ft. above sea level.”
It was a poetic place from which to observe such a powerful and fleeting event. “I remember thinking about Venus being the most volcanic world in the solar system and there I was on one of the biggest volcanoes of all,” said Kerss. “A transit of Venus is the closest our planet can ever come to another planet. For one magnificent moment I could almost imagine seeing another volcano on Venus pointing back at me.”
Kerss was 26 at the time. He’ll be 131 by the time the next transit of Venus comes along. He took the fabulous image shown at the very top of this article, which also shows significant solar activity while the transit of Venus was taking place.
Italian astronomer Galileo Galilei was the first person to predict that a transit of Venus would occur. He was born and died between two transit periods, so he never actually witnessed one.
From Earth it’s only possible to see two planets journey across the Sun’s disk—Venus and Mercury, the inner or “inferior” planets. The outer planets appear only to pass behind the Sun from Earth’s perspective.
The last transit of Mercury occurred on November 11, 2019 and it will happen next on November 13, 2032. They’re more common, happening about 13 times each century. Venus is five times the diameter of Mercury, so a transit of Venus is much more dramatic than a transit of Mercury.
The transit method is primarily how astronomers find exoplanets. NASA’s Kepler Space Telescope observed almost 200,000 stars in a tiny patch of sky between 2009 and 2018, looking for a slight dip in starlight as planets transited across their host stars.
Kepler found a whopping 2,392 exoplanets this way. NASA’s Transiting Exoplanet Survey Satellite (TESS) is now doing the same and some think it could find as many as 12,519 new expoplanets by 2024.
It is possible to see transits from other planets, though you can’t see a transit of Earth across the sun unless you’re on Mars or further out. The next transit of Earth as seen from Mars will take place on November 10, 2084.