Hundreds of Utahns gathered to watch a rare astronomical event Monday afternoon as the planet Mercury crept across the edge of the sun.
Technically, the event is called a transit of Mercury. The only other planet whose orbit brings it between the sun and Earth is Venus.The biggest collection of sun-gazers was in the parking lot of Harmon's food store, 7800 S. 700 East, Midvale. Hansen Planetarium's Patrick Wiggins said about 200 showed up for the afternoon display, watching through telescopes of all sizes. People lined up to peer through scopes equipped with special solar filters that cut out nearly all of the sun's rays, making the views safe.
Otherwise, looking at the sun through a telescope would result in blindness.
The event was broadcast on the Internet live from Utah, (http://www.worldwideutah.com). The site maintains an archive of the transit images.
Twenty to 30 students and university employees studied the transit through a large telescope in an observatory at the University of Utah. The observatory is on the roof of the south physics building.
Elsewhere on campus, a pair of telescopes was set up on the lawn, one offering filtered views through the eyepiece while the other projected an unfiltered image of the sun onto a screen.
"Mercury looked like a mole at the edge of the sun," said a physics student. A small black spot crept across part of the sun's edge, taking about an hour to make the transit.
At the end of the event, he added, "I saw Mercury slowly disappear at the edge of the sun."
The last time a transit of Mercury was visible from this part of the world was in 1973. The diminutive planet, closet to the sun, circles our nearby star every 116 days, but because its orbit is tilted relative to Earth's, it lines up with Earth only once in 23 orbits.
The most recent Mercury transits were in 1970, 1973, 1986 and 1993.
Adding to the viewers' excitement were flotillas of massive sunspots, far larger than the planet. The 11-year solar cycle is approaching the maximum level, when sunspots are most common.
In one series of photographs of the transit, on the negatives the sun's disk is between the size of a penny and a nickel. When one examines it with the naked eye, even knowing exactly where to look, Mercury is not visible. But when the negative is examined by magnifying glass, it shows up as a tiny dot near the edge of the sun.
The impression is driven home forcefully, teaching us something about the scale of our solar system: a vast star is circled by an incredibly tiny planet.