ST. GEORGE – Sky watchers are in for a rare treat as a transit of Mercury occurs Monday morning when the tiny planet Mercury moves directly between the Earth and the sun.
While the event cannot be seen with the naked eye — and it is dangerous to try — St. George Astronomy Group is offering the public a chance to view the event through special solar-filtered telescopes starting at 9 a.m. at St. George Town Square. The viewing opportunity is being co-sponsored by the St. George Library.
“You will need a telescope with magnification to observe it, either by direct viewing with a solar filter or by projection,” St. George Astronomy Group spokesperson John Mosely said in a news release. “Mercury is too small to see with the unaided eye by any method.”
During the transit, an observer can see Mercury silhouetted in front of the sun’s disk, Mosely said, but because Mercury is 52 million miles from the earth, it will look like a tiny black dot smaller than most sunspots.
This transit will be visible throughout North America, Mexico, Central America, South America and parts of Europe, Asia and Africa.
Transits of Mercury occur during either early May or early November. During May transits, Mercury appears to be 1/158th the size of the sun, according to NASA.
“These events are rare,” Mosely said, “the last transit of Mercury was in 2006, and the next won’t be until November 2019.”
Mercury’s motion is very slow, and the transit will take several hours. It will begin at 5:42 a.m. MDT — before the sun rises — and last until 12:42 p.m., Mosley said.
From Earth, only transits of the inner planets Mercury and Venus are possible, and transits are far rarer than solar eclipses. Only 13 transits of Mercury happen each century, on average.
For a full listing of skywatching events in 2016, see Skywatcher Alert: 2016 night sky celestial events calendar.
Viewing safety – Warning!
Never view the sun directly with the naked eye or with any unfiltered optical device such as telescopes, binoculars, cameras, other magnification lenses and even regular sunglasses.
It is especially tempting to look at the sun during a transit, but damage to your eyes is permanent. The sun is far too bright to look at without proper eye protection.
In this case, Mercury will not be visible without the magnification of a telescope with a solar filter or projection.
“The center part of your vision, the macula, is the most sensitive part of your vision, (it delivers) your ability to see detail; and your focus when you look straight at something comes from the macula,” Dr. Paul Gooch of SouthWest Vision in St. George told St. George News before the 2012 solar eclipse.
“It has a high concentration of photo receptors, everything is finely ordered. As a matter of fact, to stare at the sun leaves a central blank spot in your vision. So in the most severe cases of this, similar to macular degeneration, if they view (the sun) wrong they wouldn’t be able to see faces, read fine print.”
Solar viewing glasses have lenses that are actually metallic – almost like looking through tin foil – and are a must to avoid irreparable damage to the eye. This transit will not be visible using solar viewing glasses – a properly filtered telescope is required.
For more information about safe sun viewing and how to use a binocular projection technique to safely view sunspots and transits, see NASA’s spaceweather.com Safe Sunwatching Web page.
- What: Transit of Mercury viewing party sponsored by St. George Astronomy Group and the St. George Library
- When: Monday, May 9 | 9 a.m. to 12:40 p.m.
- Where: Town Square in St. George, 50 S. Main St., adjacent to the St. George Library
- Cloudy weather will cancel the event
Copyright St. George News, SaintGeorgeUtah.com LLC, 2016, all rights reserved.