During a rare, natural occurrence, the sun will darken slightly in the morning on Tuesday, June 8 – so slightly that many people won’t even notice it. Yet something historic will have occurred – the transit of Venus across the face of the Sun. Mercury and Venus are the only two planets that go in between the Sun and the Earth, and now, after 122 years, the Sun, Venus and Earth are all aligned in a direct line.
Left: The path of Venus in front of the Sun
Astronomers and would-be astronomers are invited to view this occurrence on Tuesday at 5am sunrise, from York’s Astronomical Observatory on the 4th floor of the Petrie Science & Engineering Building. Venus’s first contact with the Sun will be at 1:19am and the last contact at 7:23am. Because looking directly at the sun without proper precautions is extremely dangerous and can cause blindness, York is making special filters and equipment available at the observatory.
What is the transit of Venus?
This is among the rarest of astronomical events. The last transit seen and recorded by humans occurred in late 1882. Transits of Venus have a strange pattern of frequency. First, the solar system goes without a transit for about 121 ½ years. Then there will be one transit (such as this one in 2004) followed by another transit of Venus eight years later (this time, in the year 2012). Then there will be a span of about 105 ½ years before the next pair of transits occur, again separated by eight years. Then the pattern repeats.
Right: Image of Venus
If Venus and the Earth orbited the Sun in the same plane as the Sun, transits would happen frequently. However, the orbit of Venus is inclined to the orbit of Earth, so when Venus passes between the Sun and the Earth every 1.6 years, Venus usually is a little bit above or a little bit below the Sun, invisible in the Sun’s glare.
This transit was used to determine the exact distance between Sun and Earth. On Tuesday, June 8, Venus will appear as a small black spot slowly moving across the solar disk.
Where in the world can the transit be viewed?
The beginning of the transit will be visible from northern and western portions of Alaska, all of Asia, Indonesia and Australia, the eastern half of Africa and northern and eastern Europe, as well as the northernmost parts of Greenland.
The end of the transit will be visible over central and western Asia, all of Africa, Europe and Greenland, as well as the northernmost and eastern sections of North America and northern and eastern parts of South America.
Australians will be able to catch the beginning stages before sunset. Europeans will be able to see most, if not all of the transit, starting at around sunrise with the end coming in the early afternoon with the Sun high in the sky. For much of the eastern United States and Canada, the Sun will rise with Venus already on its disk, with the transit nearly over.
Galileo Galilei in 1610 was the first human to actually see Venus as more than just a bright point of light in the sky. Johannes Kepler, meanwhile, was shaking up the world by his meticulous use of astronomical data assembled by Tycho Brahe. What he discovered during these laborious hand calculations was that Venus would pass in front of the Sun on Dec. 6, 1631, but the transit was not visible from Europe at all.
There is no known sighting of this transit in recorded history until British cleric Jeremiah Horrocks and his friend William Crabtree spotted it on Dec. 4, 1639, and that is only because Horrocks had mathematically predicted this transit using better data than Kepler had used.
In 1984, “the astronomical scrapbook” published this quote by astronomer Joseph Ashbrook (1918-1980): “For those who witness the transit of June 8, 2004, there comes the awesome thought that not a single human being remains alive that observed the last transit of Venus, in December, 1882.”
The next transit will occur eight years later on June 6, 2012, visible in its entirety only from the Pacific Ocean and the extreme east coasts of Siberia, Japan and Australia. (North Americans will see the opening stages before sunset.) Then it will be a long wait once again until December 11, 2117.