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January 2010: Latest Sunrise, Annular Solar Eclipse & Mars at Opposition


Year's Latest Sunrise in First Week of January

At middle latitudes in the United States, the latest sunrise of the year falls on or near January 4 annually. That's in spite of the fact that the shortest day of the year (in terms of daylight) falls some 2 weeks earlier, on the December 21st solstice. For an explanation of this rather baffling phenomenon, read Latest Sunrise of the Year not on Year's Shortest Day.

Annular Solar Eclipse on January 15

Total and Annular Solar Eclipse DiagramAn annular eclipse differs from a total solar eclipse in that the Moon is too far away from Earth to totally cover over the Sun's disk. In this kind of eclipse, a thin ring - or annulus - of sunshine surrounds the New Moon silhouette. Because this eclipse takes stage in the world's eastern hemisphere, it won't be visible at all from the Americas. For more information on this eclipse, click here. (Diagram on right, courtesy of Wikipedia Commons.)
This January 15, 2010 annular eclipse deserves an honorable mention for being the longest enduring annular eclipse for the millennium (2001 to 3000). If you were at the right spot in the Indian Ocean, you'd see this eclipse lasting 11 minutes and 11 seconds. A longer annular eclipse won't be in the works until December 23, 3043.
Long-lasting annular eclipses depend on the convergence of four factors: (1) New Moon (2) Moon at or near node - point where lunar orbit crosses Earth's orbital plane (2) Earth at or near perihelion - closest point to Sun for year (3) Moon at or near apogee - farthest point from Earth for month.
In 2010, the Earth reaches perihelion on January 3, and the Moon swings to apogee on January 17. When the New Moon crosses its node in close conjunction with Earth near perihelion and the Moon near apogee, an annular eclipse is not only possible but inevitable, because the lunar disk is too small to totally cover over the Sun.
Given optimal condtions, an annular eclipse can last as long as 12 minutes and 30 seconds. The most recent annular eclipse to last 12 minutes or longer took stage on December 24, 1973. The next 12-minute showing won't be until January 14, 3080.

Mars at Oppostion

Mars comes closest to Earth for the year on January 27, 2010, and reaches opposition on January 29, 2010. For more about seeing Mars at its brightest and best in 2010, read the January 27, 2010 feature on EarthSky.

copyright 2009 by Bruce McClure

December 2009 Feature * February 2010 Feature