| Solar System Event |
The 2006 Transit of Mercury
| | Scott W. Roberts | June 27, 2006 |
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On June 8th, 2004 astronomers recorded fantastic imagery of the Venus transit using H-alpha filtered telescopes. This year it will be Mercury's turn.
Image courtesy of Ron Dantowitz and Dexter School |
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Mercury is the closest planet to the Sun, making its highly elliptical orbit in only 88 days, moving faster than any other planet in the solar system. Since the heavily cratered planet is so close to the Sun, its rare to see it exept during twilight. It was only 40 years ago that astronomers thought that the same side of the planet always faced the Sun. We now know that Mercury makes three rotations for every two orbits, making a Mercury day equal to nearly 59 Earth days. On Wednesday November 8th and 9th, the planet Mercury (as seen from Earth) will cross (transit) the face of the Sun. And with safe solar filtration on a telescope, you can see Mercury as few ever will. It will be second of only fourteen such transits to occur in this century, the last being in 2003. During the transit the diameter of Mercury looks very small as it quickly moves (transits) across the Sun. The entire transit event lasts approximately 4 hours and 58 minutes. |
| Events that occur in our solar system such as transits are a vivid reminder that we are indeed travelling through space about the Sun. But transits also served to give early scientists one of their first reliable measure of celestial distance. In 1716, Edmond Halley described how transits could be used to measure the Sun's distance, thereby establishing the absolute scale of the solar system from Kepler's third law. Here is a description of his observation and timings of a transit of Mercury from his paper: "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." |
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Map of partial and full transit visibility of the 2006 Mercury Transit.
Courtesy of HM Nautical Almanac Office |
| This rare opportunity to witness the entire transit of Mercury can be observed from eastern Australia, New Zealand, part of Antarctica, western North America, western Mexico, the southern coast of Chile, and across the Pacific Ocean. If you can't be in any of these locales, portions of the transit can be seen over Asia, most of Australia, and most of the Americas. Below is a table of the transit event courtesy of NASA GSFC: | Transit of Mercury 2006 | Date | 1st Contact | 2nd Contact | Greatest | 3rd Contact | 4th Contact | Min. Seperation | Sun R.A. | Sun Dec. | Nov. 8th, 2006 | 19:12 U.T. | 19:14 U.T. | 21:41 U.T. | 00:08 U.T. | 00:10 U.T. | 422.9 arc sec. | 14.925 | -16.73 | |
| This year, with the advent of affordable H-Alpha and Calcium K telescopes manufactured by Coronado Filters, you too can make history as Mercury marches on. You can learn more about the 2006 Mercury Transit at these web sites: NASA Eclipse Home Page
HM Nautical Almanac Office
U.S. Naval Observatory (PDF file) |
| Classifications: Advance Observing, The Sky Now, Walmart, Solar| 6/25/2006 - 11/10/2006 |
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