Transit of Venus

An experience shared over 200 years

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H.M Bark Endeavour. See page for author, CC BY 4.0 https://creativecommons.org/licenses/by/4.0, via Wikimedia Commons
H.M Bark Endeavour. See page for author, CC BY 4.0 https://creativecommons.org/licenses/by/4.0, via Wikimedia Commons

February 2022 — News is the remains of the scuttled ship Endeavour, commanded by Lt. James Cook, have been discovered in Newport Harbor, Rhode Island, where they lay for more than 200 years. The ship sailed to Tahiti to observe the June 3, 1769 transit of Venus. Endeavour was, of course, involved in far broader explorations of the South Pacific, but the news of her discovery reminded me of my own experience: the June 5, 2015 transit of Venus — observed 246 years after Cook — from Hiram at a public event we hosted.

James Cook's sketch of the "Black Drop" Effect observed as Venus began its transit of the solar disk.
James Cook’s sketch of the “Black Drop” Effect observed as Venus began its transit of the solar disk.

Recalling that day, the afternoon was cloudy and rainy and I thought we would miss out. But mere minutes before the silhouette of Venus was to appear on Sun’s face mists faded, clouds parted, and Sun shined brightly. I quickly finished setting up the telescopes, peered through the eyepiece to focus, and saw the same “black drop” phenomenon Cook sketched. My camera was set up too late (due to the aforementioned weather) to record the “black drop” for later sharing.

June 5, 2012 Transit of Venus photographed by James Guilford
June 5, 2012 Transit of Venus photographed by James Guilford

We hosted visitors at our mobile telescope site — the former location of Hiram Elementary School — until Sun sank below the treeline to our west, the transit still in progress. In the end more than 100 (estimated count lost) men, women, and children saw that big black dot moving across the sun. It was a lovely experience.

A transit of Venus is the passage of the planet across the face of our Sun as seen from Earth. Transits of Venus are rare; they come in pairs, 8 years apart, separated by approximately 120 years. Our next opportunity comes in December 2117. See you then?

NASA Article on Cook and the transit of 1769: https://science.nasa.gov/science-news/science-at-nasa/2004/28may_cook

— James Guilford, Stephens Memorial Observatory

2016: Our brief transit of Mercury

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Photo: 2016 Transit of Mercury. Photo by James Guilford.
Mercury’s Transit in Progress: Mercury is the tiny dot at the lower-left. Smudge near the center is a group of sunspots. Photo by James Guilford.

Our Solar System doesn’t care about the local weather. When something rare and interesting like today’s transit of Mercury across the solar disk takes place, it happens and there are no “rain checks.” And so it was this morning when the day dawned clear to partly-cloudy allowing us to glimpse the beginning of Mercury’s trek only to have the show stopped by rapidly encroaching clouds progressing to solid overcast!

Photo: Transit of Mercury blocked by clouds. Photo by James Guilford.
Transit of Mercury: Mother Earth’s atmospherics begin to block the view! Photo by James Guilford.

At the predicted hour Mercury appeared as a tiny dot, silhouetted in the lower left-hand quadrant of the Sun’s bright disk. Using special protective filters, observers on the ground watched as the small dot slowly moved inward from Sol’s limb. Here in Northern Ohio, transit watchers were treated to the beginning of the show. Much of the nation missed out entirely, cloud cover already in place at dawn!

Photo: GOES weather image, May 9, 2016.
Weather Satellite Image: Much of the US cloud-covered during the transit event.

NASA’s Solar Dynamics Observatory, a spacecraft, is unaffected by Earth’s pesky atmospherics and its technology produces some very dramatic images. One of my favorites shows Mercury about to cross between the satellite (us) and the Sun’s glowing photosphere; the planet has the active solar atmosphere as backdrop. Planet Mercury is 3,030 miles in diameter, not much bigger than Earth’s Moon, and looked every bit as tiny as it is compared with our nearest star!

Photo: Mercury's transit about to begin. Data courtesy of NASA/SDO, HMI, and AIA science teams.
The View from Space. Credit: Data courtesy of NASA/SDO, HMI, and AIA science teams.

Today’s transit of Mercury took place over several hours. For us in Northern Ohio, the transit began at about 7:12 AM Eastern Daylight Time with the Sun barely up. Midpoint of Mercury’s passage was at 10:57 AM, and the transit ended at 2:42 PM. Because of the orbital inclinations of the inner planets, the alignment needed to produce a transit of Mercury happens only about 13 times per century making even a glimpse of the event something special. After today’s, the next transits of Mercury will take place in November 2019, November 2032, and November 2049.

At least we won’t have to wait for so long as we must for the next transit of Venus — that happens in December 2117.