Image: NASA SOHO

Transit of Mercury

2019 November 11

Monday, 7:35 a.m. - 1:04 p.m. EST

 

During the transit, Mercury appears as a tiny dot slowly gliding across the face of the sun.  To witness this phenomenon, you need to view a magnified image with proper solar protection.  Unlike Venus in transit, in which the planet is big enough for the human eye to discern without magnification, Mercury is smaller and more distant.  On Nov. 11 the planet diameter appears a mere 10 arc-seconds across.  For comparison, Venus is about 60 arc-seconds (one arc-minute) across, and the sun is about 30 arc-minutes (half a degree) across.

 

In 1677, at age 20, astronomer Edmond Halley witnessed a transit of Mercury from the  island of St. Helena.  Decades later, in 1716, Halley wrote of his new method using the transit of an inferior planet (i.e., Mercury or Venus) to measure the size of the solar system.  Because Venus is closer and yields a larger parallax, Halley appealed for global expeditions to time the next transit of Venus.

Approx. Contact Times

(geocentric, in Universal Time):

 

1st Contact:      12:35

2nd Contact:    12:37

Greatest:          15:20

3rd Contact:     18:02

4th Contact:     18:04

2019 Transit of Mercury

 

Map by Xavier Jubier

Next Transit of Mercury:

 

2032 Nov. 13 (map)

Images from previous years

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All dressed up and no place to go (cloudy) in 2016.

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Gear packed for 2016 transit of Mercury, but cloudy skies.

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Logo for star party features 2016 transit of Mercury path over Wilhelm Nitsche's illustration "Durchgang der Merkur," circa 1852.

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Durchgang de Mercur

Illustration depicts transit of Mercury with planet being exaggerated in size and visible. From "Durchgang des Merkur" by Wilhelm Nitschke, ca.1852.

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The SOHO spacecraft observes a transit of Mercury in 2003 from space, with a time-lapse showing the path of the planet.

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A crowd heads for solar-filtered telescopes during the 2006 transit of Venus.

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An observer uses a Sunspotter to track the 2006 transit of Mercury.

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Observers queue up to witness the 2006 transit of Mercury with a solar filtered telescope near the Penn-Harris-Madison (PHM) Planetarium in Mishawaka, IN.

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Johann Doppelmayer illustrates the path of Mercury across the face of the sun for the November 6, 1720, transit of Mercury. From Atlas Coelestis, 1742.

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Youths observe Mercury on the sun with a Sun Funnel in 2006.

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Because "the cusps will appear undulating and diffused; and for a few seconds it will be doubtful whether contact has or has not taken place...the best the observer can do is watch for the phase represented by disk I...The moment of true contact is that at which the undulation of true sunlight across the dark space is just beginning." From "Reports on Telescopic Observations of the Transit of Mercury, May 5-6, 1878."

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In 2006, the public observes the transit of Mercury outside the Penn-Harris-Madison (PHM) Planetarium in Mishawaka, IN.

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On a paper plate representing the sun, an observer of the 2006 transit of Mercury records a sunspot and a smaller dot representing the silhouette of the planet.

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A "white light" solar filter, when held up toward the sun, blocks the transmission of all light except a fraction of the sun, while the side facing the observer reflects the scene behind the observer.

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The SOHO spacecraft catches a transit of Mercury in 2003 in a series of wavelengths that yield a composite image of the celestial event.

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Transit of Mercury, 1914 November 7, photograph taken at Greenwich; image courtesy of Laurence Marschall.

Telescopic Observations, 1878

Reports on Telescopic Observations of the Transit of Mercury, May 5-6, 1878. Includes individual reports from Asaph Hall, William Harkness, J.R. Eastman, Edward S. Holden, and Dr. Henry Draper.

Transit Art on Celestial Atlas

In 1742, Johann Doppelmayer features transits of Mercury and Venus in Atlas Coelestis while describing phenomena associated with the inferior planets (Plate 7). Inset shows personified Mercury and Venus passing between the earth and the sun, depicting the circumstances that create a transit.

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The black drop effect is incorrectly attributed to "a very variable amount of irradiation of bright images on the retina," though with caveats. From "Reports on Telescopic Observations of the Transit of Mercury, May 5-6, 1878."

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While a large sunspot is apparent near the limb of the sun, the small dot of Mercury in transit is also visible.

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Arrangement of Dr. Henry Draper's equatorial-room and of the instruments at Dr. Draper's Observatory. From "Reports on Telescopic Observations of the Transit of Mercury, May 5-6, 1878."

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A Sun Funnel captures the planet Mercury near the limb of the sun in 2006.

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You can make your own Sun Funnel for observing the sun safely with a telescope. Instructions are free and online at http://tinyurl.com/sunfunnel.

Blogs tagged "transit of Mercury"

Until start of 2019 transit of Merury at 07:35 a.m. EST, as seen from center of earth (geocentric).  Your time will vary.

For 2019 transit of Mercury simulations for your city, see timeanddate.com.
Observe Safely

Do not observe Mercury near the sun without proper eye protection.  You can make a Sun Funnel for an existing telescope to project a magnified image of the sun safely. 

Here is an authoritative talk about eye safety by Dr. Ralph Chou:
https://youtu.be/4RGr9FcBrSM.

 

He notes, #14 welder's glasses are falling out of favor, for polycarbonate filters must have gold filter to attenuate the dangerous UV rays, and not all have the gold filter.

 

Or read Dr. Chou's  summary of eye safety excerpted from my transit of Venus website:

Viewing the Transit and Eye Safety.

Purchase Black Drop Effect coffee from Victorian Pantry in Granger, IN.

See Fred Espenak's handiwork

for transit specifics.

2016 Links

These 2016 sites may help you prepare for the next transit of Mercury, including images and other content from previous transits of Mercury.

Note: See PDF for general Transit of Mercury links
(Web host discontinued list here in 2020.)

Chuck's Links

Here are items I created that can be used for Transit of Mercury outreach. 

Note: See PDF for Transit of Mercury links for content created by Chuck Bueter
(Web host discontinued list here in 2020.)

Among the linked content:

  • Build a Sun Funnel

  • Previous Centuries

  • Black Drop

  • Black Drop Effect Coffee

  • Eye Safety

  • Cosmic Cocktail

  • PHM Images 2006

  • Classroom Astronomer

  • PHM 2006 Recap

  • 4-Minute Transit Video

  • 2016 View From South Bend

Halley's Big Idea

Dr. Edmund Halley
Philosphical Transactions Vol. XXIX (1716)
A New Method of Determining the Parallax of the Sun,
or His Distance from the Earth, Sec. R. S., N0 348, p. 454

Translated from the Latin

 

"While I was making my observations in the island of St. Helena, about 40 years since, on the stars round the south pole, I happened to observe, with the utmost care, Mercury passing over the sun's disk: and contrary to expectation, I very accurately obtained, with a good 24-foot telescope, the very moment in which Mercury, entering the sun's limb, seemed to touch it internally, as also that of his going off; forming an angle of internal contact. Hence I discovered the precise quantity of time the whole body of Mercury had then appeared within the sun's disk, and that without an error of one single second of time; for, the thread of solar light, intercepted between the obscure limb of the planet, and the bright limb of the sun, though exceedingly slender, affected my sight, and in the twinkling of an eye, both the indenture made on the sun's limb by Mercury entering into it, vanished, and that made by his going off, appeared. On observing this I immediately concluded, that the sun's parallax might be duly determined by such observations, if Mercury, being nearer the earth, had a greater parallax, when seen from the sun; for, this difference of parallaxes is so very inconsiderable, as to be always less than the sun's parallax, which is sought; consequently, though Mercury is to be frequently seen within the sun's disk; he will scarcely be fit for the present purpose.

There remains therefore Venus's transit over the sun's disk..."

 

From http://eclipse.gsfc.nasa.gov/transit/HalleyParallax.html

 
© 2020 Chuck Bueter