November 22, 2017

AstroEvent: A Very Looong Annular Eclipse!

One of the more unique celestial events on the calendar for 2010 occurs on Friday, January 15th; an annular eclipse of the Sun, and the longest for the millennium! An annular solar eclipse occurs when the moon is at or near apogee (its most distant point from the Earth) and/or the Earth is at or near perihelion (its closest approach to the Sun)… these happened on January 17th and January 2nd respectively, setting us up for a visually large Sun and correspondingly small Moon, small enough that it won’t completely cover the Sun’s disk.   The maximum possible duration for an annular eclipse is 12 minutes and 24 seconds and the actual maximum for this eclipse is 11 minutes and 7.7 seconds, which occurs off of the southwestern coast of the Indian subcontinent.

This record will not be surpassed until the year 3043! Of course, by then, we’ll all be disembodied brains in jars, or slaves of the Antarean masters, or some such bizarre fate…in any event, the path of annularity touches down in Congo in central Africa at sunrise, passes between Mogadishu and Malindi, Kenya on its way out to the Indian Ocean, then almost squarely over Male, the capital of the Maldives on its way to passing over the southern tip of India and the northern half of Sri Lanka. Final landfall will cross Burma, for a sunset annulus over the east coast (facing westward, of course!) of China. Viewers from Eastern Europe, Asia and the remainder of Africa will get varying degrees of partiality. Don’t forget to wear eye protection even during the annular phases; a 99% blocked Sun can still be deceptively bright!

The Astro-word for this week is Antumbra. This is the technical term for the shadow of the moon that produces the bright annulus, or ring that we see during an annular solar eclipse. Think of the dark cone, or umbra, as extending behind the Moon but not quite reaching the surface of the Earth during and annular eclipse. Eclipses can even be hybrid, with a portion of the path being total and another part being annular. We were lucky to witness an annular eclipse of the Sun from Sandusky, Ohio, in 1994… but we’ve yet to check a total off of our list!

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