Observe the Transit of Mercury
Mercury transiting the surface of the Sun on November 8, 2006. You certainly need a telescope to see it's tiny disc in transit!
photo credit:  Eric S. Kounce of the West Texas Astronomers (www.wtastro.org), photographed 11-8-06

Mercury's tiny disc will transited the surface of our Sun on May 9, 2016.

See the Solar Dynamic Observatory's video of this event. 

Transits occur when a planet or another body moves in between another distant body and an observer. You may remember the famous transit of Venus that took place in 2012, when Venus passed between Earth and the Sun. Millions of people watched using safe solar observing equipment as Venus's large disc passed in front of our Sun. The Kepler space telescope observed thousands of transits to find evidence of planets orbiting other stars. This coming transit will not be as easy to observe as Venus's four years ago,  but is still interesting in its own right and for many people this may be the only time they see the planet Mercury. Only Venus and Mercury transit our Sun from our point of view, since they are the only two large planetary bodies in between Earth and the Sun. Jupiter, for example, being much further out from the Sun than Earth, will never transit the Sun, since it will never move in between the Sun and Earth.

The transit took place on May 9, between, starting on around 11:10 UTC and ending at approximately 18:44 GMT, lasting approximately seven and a half hours- a very long transit for this speedy world! For observers in the United States, this means that the entirety of the transit was visible from the East Coast starting after sunrise at 7:10 am EST and ending at 2:44 EDT. Observers on the west coast caught Mercury already in transit at sunrise, but there had plenty of time to watch the rest of the transit: it ended at 11:44 am PDT.

Transits of our Sun are rare and fascinating events. Mercury is also the most notoriously hard to observe of the classical five naked eye planets, so being able to catch it transiting is quite a feat indeed! Due to its lack of an atmosphere, you can observe how crisp the edge of the disc is against the Sun if your telescope is powerful enough. You can easily watch its progress across its face and quite clearly see the speed of its orbit. This transit will be extra special for observers in North America as the next transit, while in 2019, will be a challenge to see for anyone in the continental US, and the next transit after that will be in 2032. What about Venus, the only other transiting world visible from Earth? Its next transit will be in 2117! So that makes this transit of Mercury will be the last time that many of us will be able to easily watch such an event!

Mercury is the smallest planet in the solar system and its size and distance from Earth make its silhouette far too small to be seen without the aid of a solar telescope. Unlike the transit of Venus you will not be able to see Mercury's disc crossing the Sun by using eclipse glasses or solar viewers. Catching the disc of Mercury will be very much like trying to see a small sunspot, with the exception that the planet will be even smaller, and a very sharp, defined, round dot.

Logo for the Shoot the Messenger project
Log for the Shoot the Messenger project, courtesy the Cincinnati Observtaory.

Here are our tips for making the most of the Mercury transit:
  • The Astronomical Society of the Pacific has made an issue of their quarterly magazine-fitting named Mercury-free to Night Sky Network members this month, at http://bit.ly/MercuryNSN2016. Check out the in-depth article (page 27-32) on how to observe the transit of Mercury, written by none other than Fred Espenak and Paul Deans. This feature details everything you need to know about safely observing the transit, including several projection techniques such as a sun funnel and eyepiece projection onto a cardboard card, and direct viewing through solar filtered telescopes.                          Mercury Magazine is a benefit of ASP membership and features articles showcasing the latest developments in astronomy as well as society news and monthly sky events. Join the ASP to receive this beautiful digital magazine and support astronomy education: http://www.astrosociety.org/get-involved/asp-membership/
  • Find out the latest on Mercury by watching our recent webinar on Mercury and the MESSENGER space probe with Dr. Larry Nittler on Youtube: http://bit.ly/NSNMESSENGER2016
Good luck, and may you all have clear and warm morning skies for this rare celestial event!

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