2016, May 9: Transit of Mercury


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Never view the sun directly.  Project the sun on a flat surface using a mirror.

On May 9, 2016, just after Mercury makes its best appearance of the year, it passes nearly directly between the earth and sun.  From our planet, Mercury passes across the face of the sun — a transit.  Mercury’s rapid orbit around the sun carries it between Earth and our central star every 116 days.  Normally, as Mercury passes between these celestial wonders, it is not in a direct line with them; it appears to pass above or below the sun.

Mercury crosses in front of the sun 13-14 times a century and currently this can occur during the months of May and November, when the tilted orbit of this speedy planet crosses the earth-sun plane.  Following this event, the next transit of Mercury is November 11, 2019.

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This chart shows the path of Mercury in front of the sun on May 9. (Click the image to see it larger.)

As seen from Chicago, the sun rises at 5:37 a.m. CDT.  The transit begins at 6:13 a.m. CDT when the edge of Mercury touches the edge of sun.  The sun is low in the sky, only 6 degrees when this occurs.  By 6:16 a.m. CDT, Mercury’s disk is completely in front of the sun.  Mercury slowly inches across the sun during the morning.  The entire event takes 7 hours, 28 minutes.  By 9:58 a.m. CDT, Mercury reaches the Greatest Transit Point, the point when it is closest to the sun’s center.  By 1:38 p.m. CDT, Mercury’s final appearance in front of the sun occurs and the speedy planet begins moving from the sun’s face.  By 1:41 p.m. CDT, Mercury leaves the sun’s face and the event is over.

It is important to never look directly at the sun.  Group viewing of the event can occur with a solar projector.  Cut a dime sized hole in a sheet of paper.  Cover a mirror with the paper.  Reflect the sun’s image on a flat surface.  Mercury appears as a small dot in front of the sun.  If sunspots are present, they will appear as well.

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