On Monday, May 9, most people on Earth will be able to look up and watch Mercury pass in front of the sun, something that hasn’t been seen in almost 10 years.

The transit of Mercury occurs about 13 times every 100 years, with the next one coming in 2019, according to Space.com.

While most will be in the line of sight to see the passing, there will be some areas blocked from seeing a silhouette of Mercury float across the sun.

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Places like eastern Asia, including Japan, Oceania and Antartica will miss out on the transit, according to Royal Astronomical Society. Those who can’t witness the event for themselves will be able to watch online, however.

Both Venus and Mercury are the only planets between us and the sun, meaning they’re the only two we have the chance of seeing a transit. However, because the planets don’t sit on a flat orbit with one another, transits don’t happen every time a passing planet orbits.

Mercury tends to transit the sun in early May or November, which is normally when the Earth’s and Mercury’s orbital planes cross each other, NASA’s Goddard Space Flight Center reported. During the last 7 centuries, about two-thirds of Mercury’s transits have occurred in November.

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The apparent size of Mercury against the sun changes depending on when it passes, also. During the November transits, Mercury is 1/194 the size of the sun, compared to 1/158 when it passes in May.

For those who want to watch the event take place, it’s advised that you find a safe way to use a telescope or binoculars, because staring directly into the sun can be detrimental to your health.

One way is to project the magnified Sun from a telescope or pair of binoculars backward onto a light colored surface. Mercury will appear as a black dot against the surface, eliminating the confusion between the planet and a sunspot, according to Naked Eye Planets. Another way to view the transit is to attach an aluminized solar filter on the front of the telescope.

The transit will last a total of about 7 and a half hours.

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