During a transit, Mercury passes between Earth and the sun, becoming a small, round silhouette against the yellow glow of the solar disk.
NASA says the transit is a teachable moment for orbital mechanics: Even though Mercury swings around the sun every 88 days, not every passage results in a transit across the sun's disk as seen from Earth.
The entire 5 ½-hour event will be visible, weather permitting, in the eastern USA and Canada, and all Central and South America. The planetarium warned that the sun should never be looked at through a telescope without proper filters. At about 10:30 a.m. on November 11, Mercury will be near the midpoint of the transit and closest to the center of the sun. For those on the western coast of the Americas, the transit will already be underway at sunrise, while viewers in most of Africa, Eastern Europe, and the bulk of Asia will still see the transit in progress as the sun sets.
A multiple-exposure image from NASA's Solar Dynamics Observatory shows Mercury's track across the sun's disk in 2016. Periodic, fleeting dips of starlight indicate an orbiting planet.
The transit of Mercury in front of the sun will happen Monday, a rare event that won't be seen again until 2032. Earthlings get treated to just 13 or 14 Mercury transits a century. The next one isn't until 2117. North Americans will have an even longer dry spell to contend with, as they will have to wait until 2049 for the next Mercury transit visible from their part of the globe. When Mercury's leading edge first touches the sun, the planet will appear to grow a narrow neck connecting it to the edge of the sun, making the silhouette look like a teardrop.
"Thankfully, he continued to observe for several hours and noticed that the tiny dark spot moved much faster across the face of the sun and along a different path than a sunspot would", writes Todd Timberlake, author of Finding Our Place in the Solar System.
All this understanding was nearly delayed, though, when Mercury was momentarily written off as just another spot on the sun.
While the next transit of Mercury may be in 2032, Boyd said people living in the US won't have an opportunity to see it again until 2049.
It's this kind of transit that allows scientists to discover alien worlds.
The Virtual Telescope Project 2.0 is planning to broadcast the event live via a webcast.