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Mar 26 2012

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March 26th: Sun Shines Directly Over Equator from a Spot in the Indian Ocean

Blue Marble Earth
This composite image uses a number of swaths of the Earth’s surface taken on January 4, 2012.
CREDIT: NASA/NOAA/GSFC/Suomi NPP/VIIRS/Norman Kuring

Across much of the United States, this has been an unusually mild winter, especially for those living east of the Mississippi. Not a few people have noted that spring seems to have come early this year. Of course, in a meteorological sense that could be true, but in 2012 it will also be true in an astronomical sense as well, because this year spring will make its earliest arrival since the late 19th century: 1896, to be exact.

The vernal equinox — the first day of spring — arrived March 20 at 05:14 Universal Time, or 1:14 a.m. EDT. Even more intriguing is that for those in the Mountain and Pacific Time zones, the equinox actually arrived March 19.

Astronomers define an equinox as that moment when the sun arrives at one of two intersection points of the ecliptic (the sun’s path across the sky) and the celestial equator (Earth’s equator projected onto the sky). One such intersection point is located in western Virgo; the sun arrives there on Sept. 22 or 23, and appears to cross the equator from north to south, marking the beginning of autumn in the Northern Hemisphere.

The other intersection point, in eastern Pisces, is where the sun was on March 20th. The sun is now migrating north of the equator, hence this is the “vernal” or spring equinox. At 5:14 UT Tuesday March 26th, the sun will be shining directly over the equator from the point of view of a spot in the Indian Ocean, 757 miles (1,218 km) southeast of Colombo, Sri Lanka. [Earth’s Equinoxes & Solstices (Infographic)]

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