Look Up, America: There’s a ‘Blood Moon’ Tonight

Fingers crossed for cloudless skies for this rare celestial phenomenon.

National Journal
Marina Koren
April 14, 2014, 10:30 a.m.

Hal­loween may be months away, but the night sky is about to get pretty spooky.

A total lun­ar ec­lipse will be vis­ible across North Amer­ica late Monday night, and the en­tire con­tin­ent­al United States will get a clear view of the oc­cur­rence, weath­er per­mit­ting. The Earth, cur­rently po­si­tioned between the sun and the moon, will cast a shad­ow over the moon’s en­tire sur­face. The moon will then glow red, vary­ing in col­or from bright cop­per to crim­son — hence the nick­name “blood moon.”

Omin­ous as they might seem, red moons are com­pletely nat­ur­al products of total lun­ar ec­lipses, which oc­cur in stages and last for a few hours.

First, the moon’s edge be­gins to enter the out­er por­tion of the Earth’s shad­ow, known as its pen­um­bra. Some shad­ing along the moon’s sur­face be­gins to ap­pear, chas­ing the light that still reaches the ce­les­ti­al body from the sun.

Then the moon enters the um­bra, the darkest part of Earth’s shad­ow. “Few sights in as­tro­nomy are more eer­ie and im­press­ive than watch­ing this red-black shad­ow creep­ing, minute by minute, across the bright lun­ar land­scape, slowly en­gulf­ing one crater after an­oth­er,” writes Alan Mac­Robert at Sky & Tele­scope. An hour later, only a bright sliv­er of the moon re­mains out­side the shad­ow.

That’s when the red­dish hue be­gins to ap­pear, and the source of the col­or is noth­ing short of mind-bog­gling. Be­cause the Earth is between the sun and the moon, sun­light must first pass through our plan­et’s at­mo­sphere be­fore reach­ing the moon. As sun­light skims the rim of the globe, our at­mo­sphere bends and scat­ters it. When the re­frac­ted light from all the sun­rises and sun­sets from around the Earth hits the moon, it casts a red glow on the sur­face.

Un­like a sol­ar ec­lipse, a lun­ar ec­lipse can be seen with the na­ked eye if the sky is clear. It also won’t blind you when you stare dir­ectly at it. Here’s what a total lun­ar ec­lipse looked like in 2011, the last time North Amer­ica wit­nessed one:

This time around, the ec­lipse will last from about 1:20 a.m. un­til 5:33 a.m on the East Coast, with the moon at its blood­i­est at 3:07 a.m. West Coast dwell­ers don’t have to stay up too late to catch the show, which be­gins at 10:20 p.m. and ends at 2:33 a.m. For oth­er time zones, check out this handy chart from Sky & Tele­scope. Or plug in your city at this U.S. Nav­al Ob­ser­vat­ory data gen­er­at­or to de­term­ine peak view­ing times. Or, if you want to watch from the com­fort of your own bed, tune in­to NASA TV.

Monday night’s ec­lipse is the first of series of four total ec­lipses vis­ible in North Amer­ica in the next year. The phe­nomen­on is called a tet­rad, and it’s quite rare. For ex­ample, between 1600 and 1900, no com­plete lun­ar ec­lipses were seen at all. This cen­tury, however, is more prom­ising, NASA’s Fred Es­penak, who spe­cial­izes in ec­lipse pre­dic­tions, told ABC‘s Eliza­beth Gonza­lez on Monday. “Fre­quency sort of goes through 585-year cycles,” he said. “So you go through cen­tur­ies where you don’t have any, and cen­tur­ies where you have a num­ber of them.”

If we’re talk­ing in cen­tur­ies, the next tet­rad will be here be­fore we know it — in 2032.

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