Transit of Mercury on November 11

The planet Mercury will pass directly between the Earth and the Sun on the morning of November 11. Such an occurrence is called a transit, and it means that Mercury will be visible (through telescopes — the planet is far too small to see with the naked eye) against the Sun.

The Casper Planetarium will have telescopes equipped with solar filters set up on our lawn from 9:30 to 10:30 am on November 11th. Anyone is welcome to stop and take a look at the transit. But — don’t expect a spectacular show. Because the planet is so small, it will appear as a tiny dot, almost like a fleck of dust. In this photo from 2016’s transit, note that the planet is smaller than the sunspot visible in the same shot.

IMPORTANT SAFETY NOTE: Never look directly at the Sun, whether with naked eyes or through a telescope, without proper eye protection — eclipse glasses for your eyes, or a properly installed solar filter for your telescope. Permanent eye damage, even blindness, could result.

One interesting thing to note about transits in general … they are one of the principal tools in the exoplanet hunter’s tool kit. When any planet transits across its star, it blocks a portion of the light emitted by that star. Sensitive telescopes like NASA’s TESS and KEPLER capture multiple images of distant stars, and when the amount of light coming from those stars dips and rebounds, one possible cause is the transit of a planet. (TESS stands for Transiting Exoplanet Survey Satellite.) So who knows … this transit of Mercury could be signaling astronomers on some far distant world that planets exist around the little star called Sol.

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