Mercury Crossing The Sun For The First Time In A Decade

Mercury and the sun have begun to dance  in a rare astronomical phenomenon you won't want to miss.

In what's known as a planetary transit , the solar system's smallest planet will appear as a tiny black spot slowly crossing the face of our star.

It's the first time the event has occurred in a decade, and those who miss it will have to wait until 2019 for the next opportunity.

The 7.5-hour transit runs from 7:12 a.m. EDT, when Mercury will "start to make a tiny dent in the sun's disk ," and until 2:42 p.m. It will be visible in its entirety across the U.S. East Coast, as well as in South America, western Europe and western Africa, according to NASA. Those located in Western U.S. states will be able to view it after sunrise. 

It won't be visible to the naked eye. If you don't have your own gear, don't worry. NASA will be streaming the transit  live on NASA TV and its Facebook page . You can also watch it live in the video above, courtesy of the robotic telescope company Slooh.

As the planet makes its "leisurely journey across the face of the sun ," it will appear 1/158 the size of the sun, according to NASA.

"Astronomers get excited when any two things come close to each other in the heavens," Louis Mayo, program manager at NASA’s Goddard Space Flight Center, said in a statement. "This is a big deal for us."

Mercury transits the sun roughly 13 or 14 times per century. The last one occurred in 2006 , with the next two not until Nov. 11, 2019, and Nov. 13, 2032. 

For those observing Monday's event with their own telescope, NASA offers these important safety tips : "Use only a commercially available safe solar filter covering the sky-end of a telescope or both sky-ends of a pair of high power binoculars to observe the transit. Sunglasses and crossed polarizers are not dark enough to save your retina from burns and permanent scarring. Low-power binoculars won't have enough magnification to show tiny Mercury. The transit is NOT visible to the naked eye and cannot be detected through standard solar viewing glasses."

In advance of Mercury's exciting day in the spotlight, NASA released the first global topographic model of the solar system's innermost planet on Friday.

It may be small, but Mercury is taking center stage this week.