TRANSIT (OF MERCURY)


I have shown many the night and daytime sky. Twenty years ago, I went to a conference in Palm Desert, during which time Saturn’s rings happened to be edge-on, an occurrence every fourteen and a half years.  I was driving, so I took my telescope, set it up in the parking lot the first night and had maybe 5 takers.  The second night, I had 30.  The fourth and final night, I had a continuous line.  People were thrilled.  One woman almost cried when she realized she was looking at Saturn.  Another guy told me about his childhood, when he once knew the planets and stars.  He finished looking and got back in line.  Loved that trip.  It had been nearly 4 years since I last did a telescope-aided “star party,” when I showed maybe 50 people the 2012 transit of Venus across the Sun, an exceedingly rare event that won’t be seen again until 2117.

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TRANSIT OF VENUS, 5 JUNE 2012

Mercury transits the Sun as well as Venus, about 13-14 times a century, but I had never seen one. I looked during the November 1999 transit, when I was a grad student in Las Cruces, New Mexico, but I had no telescope, and binoculars were insufficient.  This time, I was prepared with my telescope, Mylar solar filter designed for it, and camera, with which I would shoot the transit, using a solar filter designed for binoculars that could be held over a camera lens.  I put the event on the Obsidian hike schedule, where it appeared as a “class”.  Where asked, “number of people allowed to join,” I wrote “100.”  Exactly 6 eventually signed up, including me, and one of them cancelled.  I decided to set up just south of Autzen Stadium at 7:30, during which time the transit would be well underway.  From Eugene, the transit started before sunrise.

I knew of two other local sites where people had telescopes, one downtown, the other on Skinner Butte, a wooded hill 300 feet above the city, near the Willamette River.  I hoped I might have several visitors, since my site was near a dog park and a lot of walkers were out, but it was quiet.  I arrived with my wife at 7:30, and one of the Obsidians joined us about 20 minutes later.  It was quiet, except in the celestial arena, where interesting things were happening.

Once I had the telescope focused on the Sun, I saw Mercury immediately.  It was small, but compared to the sunspot near it, the planet was a sharply defined black sphere. I shot pictures of it using high power, letting the camera gradually get the Sun into focus.

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Mercury is below the sunspot in the lower middle of the picture.

 

A few came by, but they were either wearing earphones and couldn’t hear me or not interested.  Four other Obsidians came and kept us company.  I don’t push people to view something in the sky.  I will tell them what I am doing, and if they seem interested, I suggest they take a look.  Some are very interested, some not; a woman with two dogs was more interested in showing her dogs than she was in Mercury.  She never made one move to come over and look.  People have their reasons.

Perhaps it was just as well.  I hadn’t read up on transits.  That’s inexcusable for me, and I’m a bit ashamed that I didn’t prepare my lesson plan.  Kepler predicted the first known transits of Mercury and Venus, incredibly occurring within a month of each other in 1631, but ironically and sadly, he died the year before.  His predictions were not only verified (he said to check a day on either side of the prediction, because he didn’t trust his calculations), but were within 5 hours of the correct time.

Why did it all matter? In the 17th century, we knew the relative distances the planets were from each other but not the Sun-Earth distance. Knowing that distance, known as an astronomical unit (AU), would allow us to know all the distances. The path of a planet’s crossing the Sun is different depending upon one’s location.  In other words, the path will be a different chord on the circle of the Sun for observers in different locations.  By knowing the location and the chords, one can determine the distance from the Earth to the Sun, an astronomical unit (AU).

At 11:30, four hours after arrival, we saw Mercury near the edge of the Sun.  It then became internally tangent to the Sun (third contact).  Finally, there was a slight irregularity, a little hole, on the edge of the Sun.  Mercury was continuing on its orbit, in several days becoming visible in morning twilight.

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Mercury approaching the edge of the Sun.

After I posted my pictures on Facebook, some of which were actually decent, I saw in “trending news” something about the transit, referring to it as an “astrological event.”  Worse, it was accompanied by a NASA picture.  I posted a scathing comment about the inability of so many people to know the difference between astrology and astronomy, and the distressingly large number of Americans who believe in astrology.  I later deleted the comment.

I became disheartened when I heard from a friend that not one classroom he knew of, and he was recently a teacher, had kids go outside and see REAL (caps his) science in the REAL sky.  He continued: “The kids who looked through my scopes today were awestruck at seeing a live event right before their eyes and experiencing the size of the solar system via this transit. Heard lots of ‘wows’ and ‘cools.’ Funny, I never heard that when they were watching a video on a Smartboard.”

I would have loved to have shown the transit at a school.  Had I tried, however, the first thing I would likely have heard would have been, “Who are you?”  (now, one has to be somebody, not just an experienced amateur astronomer).  Then I would have heard how busy teachers are, require fingerprinting and have a background check.  Yet, in 60 minutes of having 100 kids look at Mercury’s crossing the Sun, I bet more of them would remember this day than the day they would have at school.  It would stay with many, just like when I talk about eclipses, people remember days in school where they made pinhole cameras to view a partial eclipse.  I could have made trig, geometry and space exploration come alive.  Instead, I showed this to 10 other people.  Ten.  And I told passersby what I was doing.

Still, the fact that only 10 others saw it with me was immaterial. I made my choice; they made theirs.  We will have to wait until November 2019 for another chance here.  Climatologically, that is a cloudy time in Oregon.  Whether I would go elsewhere to see it is not clear.  I enjoyed this transit more than I thought I would, and if eastern Oregon were clear, it might be worth a trip.

Nah.  Definitely will be worth it.

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Mercury almost at the edge of the Sun.

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Talking to Evelyn N. of the Obsidians about the Transit. Photo courtesy of David Lodeesen.

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