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CosmosUp | September 22, 2023

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Rare Astronomical Events: Transit of Mercury on May 9

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A rare and amazing astronomical event is set to take place Monday, May 9th. Mercury, the smallest planet in the solar system, will pass directly between the Sun and Earth, and thus it will partially eclipse the sun. This event is called the transit of Mercury and it is the biggest and rarest astronomical events of 2016 — only happens 14 times in 100 years.

The transit of Mercury will be visible from most of the western hemisphere, actually most of the planet will get to see at least part of it with the exception of Australia, New Zealand, and several areas of eastern Asia.

You will be able to watch the transit between 7.12am (EDT) and 2.42pm if you live in USA, NASA say. As Mercury moves across the face of the sun, it will appears like a small black silhouette blocking a tiny amount of light from the Sun.

The transit will takes a long time, over seven hours, so most of the planet will see at least a part of it; To watch this event you need a telescope or any proper equipment but keep in mind: looking at the Sun without proper equipment is very dangerous. You should never stare directly at the sun; Use a telescope with with a safe solar filter.

Looking at the Sun without appropriate protection, either during the transit, or at any other time, can cause serious and permanent damage to the eyes.

explain scientists.

You can watch the brief animation by NASA showing what it will look like:

Why is it a rare event? Mercury is the closest planet to the Sun, located at an average distance of 58 million kilometers from the star. It is the smallest planet in the solar system, has a diameter of 4,780 kilometers — a little larger than our Moon; Its orbit the Sun every 88 days which is much faster than any other planet in the Solar System. Seen from Earth, it appears to move around its orbit in about 116 days.

Mercury’ orbit is very slightly tilted with respect to ours, by about 7°. So, due to the tilt of its orbit, Mercury seems to be most of the time above or below the sun, it misses the Sun’s actual disk. For this reason, the transits of Mercury across the Sun are rare, 13 or 14 per century. The last one occurred ten years ago, and the next will be in November 2019, November 2032 and May 2049.

Transit of Mercury, Mercury as seen cross by the surface of the sun

Transit of Mercury live

If you don’t have a telescope or if won’t participate to any astronomical “star party”, you can watch the whole event broadcasting online. There are a number of live streams of the transit being broadcast online. Slooh will be beginning its broadcast at 12pm GMT and it can be viewed here. Nasa will be hosting a series of events. A live stream will be taking place on Nasa TV as well as on its Facebook page.



  1. Ron Cole

    You do realize that short term astronomical events like this make the clouds roll in and rain all day right? Chance of rain all day Monday – 100%.

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