Don’t Miss This Rare Celestial Crossing Taking Place on May 9

May 2, 2016 | Joanne Kennell

The transit of Mercury
Photo credit: NASA. Black space has been added to the image.

Mark your calendars!

On Monday (May 9), a rare astronomical event will occur — you will be able to see Mercury make its way across the surface of the sun. It is called the “Transit of Mercury” and it only happens about 13 times every 100 years. The last event was in November 2006 and the next one won’t take place until 2019.

This transit will be visible either partially or fully throughout most of the world. However, according to the Royal Astronomical Society (RAS), it will not be visible in Japan, parts of Eastern Asia, Oceania and nearby island nations, or Antarctica.

So what exactly is the Transit of Mercury? It has to do with its orbit. Although both Mercury and Venus circle between the Earth and the sun, the three planets do not sit in a flat orbit to one another. In fact, it is only when Earth lines up with Mercury or Venus that the passing planet becomes visible to skywatchers as it crosses the sun.

SEE ALSO: 11 Astronomical Events You Won’t Want to Miss in 2016

Mercury’s transits either occur in early May or November. During those months the Earth’s orbital plane is intersected by Mercury’s, according to NASA. However, the orientation of the two planes can change over long periods of time. In the past 700 years, two-thirds of the transits have occurred in November.

But this year we are lucky because in May, the small planet is close to the farthest point of its elliptical orbit around the sun — meaning Mercury is slightly closer to Earth. In November, the planet appears only 1/194 the size of the sun, but in May it appears around 1/158 — a 23 percent increase in size.

Mercury’s upcoming transit can be broken into five stages: contact I though contact V. Although these stages will occur at slightly different times depending on your location on Earth, they will only vary by as much as 2 minutes, according to RAS. So you don’t have to worry about missing it. The transit will be visible between 10:25 a.m. and 2:44 p.m. EDT.

However, there is one downside to the event. Due to the apparent size of Mercury in the sky, its transit cannot be seen using pinhole projectors. Rather, the best way for amateurs to view the event is to use binoculars or a telescope. But DO NOT attempt to look at the sun without proper eye protection. Looking directly at the sun can cause permanent eye damage or blindness.

If you don’t have proper eyewear, are in a region where it won’t be visible, or just don’t want to take the risk of looking towards the sun, the Slooh Community Observatory will be hosting a free webcast of the event available at this link — all you have to do is join Slooh, but don’t worry it’s free.

Now, go mark your calendars!

You might also like: Things You Never Knew About Mercury

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