Democracy Dies in Darkness

Capital Weather Gang

Mercury will stroll in front of the sun on Monday, and you can watch it

By Blaine Friedlander

May 5, 2016 at 12:47 PM

Venus transits the sun in 2012, as seen through the special sun-research lenses of NASA’s Solar Dynamics Observatory satellite. On Monday, the observatory will capture Mercury cruise across the sun. (NASA/SDO)

There will be a little black spot on the sun Monday.

It's the rare transit of Mercury — the fastest and closest planet to the sun — slowly crossing our radiant, life-giving star over several hours on May 9, offering humanity a chance to enjoy a natural show.

Related: [People are freaking out about ‘Mercury in retrograde.’ This is what’s really going on.]

Barring cloudiness all day, you can have breakfast, lunch and an afternoon tea with the lithe little planet. The eastern United States gets to view the full 7.5-hour transit, starting at 7:12 a.m. Eastern time.

Mercury will reach its transit midpoint at 10:57 a.m., and it all ends around 2:40 p.m., according to retired NASA astronomer Fred Espenak, who runs the website.

Even the Midwest and the Western states can enjoy the transit for hours, as the cosmic performance either starts soon after sunrise or it will have been underway by sunrise in those time zones.

Take caution: Do not look directly into the sun through a bare telescope, or bare binoculars, or with your naked eye — and that includes sunglasses. If you do, you will go blind. View the transit only through proper solar-safe filters on optical instruments. Although this website is for solar eclipses, the safety principles for transits ring true.

Transits back in the day

The transits by Mercury and Venus yield key physical, scientific detail that helps us understand our place in the solar system and the universe. We get to learn the size of other planets and our sun's distance from Earth and find out how long it takes for other planets to orbit the sun. Humanity saw its first Mercury transit in 1631, a mere two decades after the invention of the telescope.

Espenak, on his EclipseWise website, explains that famed astronomer Edmund Halley realized that transits yield measurements for the Sun's distance and provide us a scale for the solar system. Expeditions in 1761 and 1769 to observe Venus transits produced the "first good value for the Sun's distance," Espenak said.

The time between Venus transit pairs is more than a century, but there are 13 Mercury transits for each century. So far this millennium, we've enjoyed Mercury transits in 2003 and 2006. Beyond 2016, the next one will be Nov. 11, 2019 — Veterans Day.

Much like eclipses belong to a "saros," or family, planetary transits belong to a long series. Monday's transit belongs to Series 7, which means that the Mercury transits on May 9, 1970, May 8, 1924, and May 6, 1878, are all in the same family. The next Series 7 Mercury transit will be May 10, 2062, and the series ends on May 13, 2154.

Where to watch


Viewing parties in the Washigton area

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