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Mercury Transit in Trinity on 11th November 2019

Mercury transiting the Sun as seen from Earth in 2006. Mercury is the smallest planet in our Solar System, with a diameter of 4,879 km, while the Sun is an enormous 1.4 million km across — about 109 times the diameter of the Earth (12,742 km) Credit: ESA/NASA/SOHO

CAUTION: Do not look directly at the Sun during the transit or at any other time. Doing so can cause permanent damage to your eyes.

On Monday 11th November 2019 a rare transit of Mercury  across the face of the Sun takes place, and will be visible for us here in Ireland. During the transit, Mercury, the smallest planet in our Solar System, and also the planet closest to our Sun will pass directly between the Earth and the Sun. This gives us the opportunity to see the tiny dark dot that is Mercury transit across the bright surface of our closest star. There are only about 13 Mercury transits that are visible from Earth every century. The next one takes place in 2032.

The School of Physics, Trinity College Dublin will celebrate this rare event, weather permitting, setting up a telescope in Trinity's Front Square on Monday, 11th of November from 12:30 noon. A large screen TV displaying real-time observations of the transit from other locations (including the Solar Dynamics Observatory satellite) will be shown allowing us view the transit even if it’s partly cloudy.  Mercury will appear as a black dot on the face of the Sun, much too small to see without magnification. But the telescope, with a special solar filter, will let members of the public see what the Sun looks like and enable them to see the tiny planet moving through space across the vast face of our Sun. There will be plenty of expert astrophysicists from Trinity’s Astrophysics Research Group on hand to talk to the members of the public about this exciting event, and to help all view the transit safely. 

An image of Mercury passing in front of the sun on Nov. 8, 2006 from The Japanese Hinode satellite. (Credit: JAXA/NASA/PPARC)

The predicted positions of Mercury for the Nov. 11, 2019, transit. The blue circles represent the apparent size of Mercury relative to the sun and are spaced 30 minutes apart. (Credit: Dean Pesnell/NASA/Solar Dynamics Observatory)

Planetary transits were hugely important throughout the history of science such as proving Kepler's revolutionary ideas that all the planets moved around the Sun in elliptical orbits, along with providing estimates of the distance from the Earth to the Sun. The transit of Venus in 1916 was used by Eddington to verify Einstein’s laws of gravity in his General Theory of Relativity. The Irish connection was that the tracking mirror used for this famous expedition was made on Observatory Lane, Rathmines, Dublin by Thomas Grubb’s company (further detail at the Royal Irish Academy )

The event at Trinity's Front Square on the 11th of November will be an exciting experience for all involved. Join us to have the unique opportunity to observe Mercury’s transit with our telescopes, talk to our scientists about the physics of our Sun, the science of planetary transits along with new and exciting missions we are involved in.

If you can’t make it to Trinity’s Front Square both the ESA and NASA will be web-streaming live images from their spacecraft and telescopes.
Further information, including safe viewing details, and teacher resources can be found at

Royal Astronomical Society Website