August 17, 2019

Spot the Lunar High- & Low-lands with the Naked Eye!

Did you happen to notice that the Moon was fat and nearly full Halloween night? The technical full Moon for November falls today, Monday the 2nd, at 2:14 PM EST (yes we’re back on standard time now; did you get to work an hour early this morning?) Of course, the full Moon, like all phases, only occurs at an instant in time. That instant is the time that the Moon is exactly 180 degrees, or 12 hours of right ascension opposite to the Sun.

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AstroEvent of the Week, January 10th-18th: The Largest Full Moon of the Year!

Does that Full Moon rising this weekend look a little larger than usual? It’s not totally an illusion, although much has been written about the “large Moon on the horizon” effect. The first Full Moon of the year will also be the largest of 2009. This is because the Full Moon on the 11th at 3:28UT (Saturday evening for the US east coast) is still occurring pretty near perigee, which happens on the the 10th at 10:53 UT 16 hours prior. I know, Decembers’ Full Moon last month was the largest of last year, as well…any collectors of obscure astronomical phenomena know how often the largest Full Moons of the Year happen back to back? Of course, it would have to be in December-January, as happened in 2008-9. This months’ Moon is also known as the Full Wolf Moon. This sets the Moon up for an annular Solar eclipse in two weeks time, as it will be very near perigee and hence too small to completely cover the Sun. The Earth itself just passed perigee for the year on January 4th; all this translates into a big eclipsed Sun/small New Moon scenario!

This weeks’ Astro-word of the week is the lunar Maria. One of the first things a lunar observer notices are these dark, flat planes that cover roughly half of the lunar nearside. Galileo mistook them for seas (that’s how poor his first handmade optics were!) and the Latin name stuck. Noticeable to the naked eye, they form the famous “man in the Moon” illusion. One of the big surprises of the space age was the near total absence of mare (the plural) on the lunar far-side! Obviously, the gravitational influence of the Earth has had something to do with their formation, but their origins still aren’t entirely clear. These Maria are now known from sample returns to be basins filled in with accumulated basaltic ejecta and dust. The Moon may look shinny and bright to a dark adapted eye, but check out some of the Apollo photos snapped from the surface sometime; the Moon is a very dark place! Astronauts returning from the surface have remarked that remnants “tracked in” to the Command Module looked like coal dust and smelled like gunpowder. So much for Swiss cheese!