Jimmy Westlake: Lunar eclipse visible next week
After being treated to four spectacular lunar eclipses in 2014-15, lunar eclipse watchers will have to settle for a very slight lunar eclipse in 2016. There are five eclipses this year, two solar and three lunar, but this will be the only one visible from Colorado.
The word eclipse comes from the Greek word that means to abandon. During a solar eclipse, when the moon passes in front of the sun, the sun abandons us for a few minutes. During a lunar eclipse, in which the full moon passes into the shadow of the Earth, the moon abandons us for an hour or so.
Earth, moon and sun do not line up perfectly for an eclipse every month. The proper alignment occurs only during the so-called eclipse seasons, windows of opportunity lasting about 34 days and separated by about six months.
When a new moon, or a full moon, coincides with one of our eclipse seasons, there will be an eclipse. The maximum number of eclipses visible in one calendar year is seven and the minimum is four.
The eclipse seasons advance about 20 days earlier in the calendar each year due to the slow wobble of the moon’s orbit around the Earth. This year, our eclipse seasons occur in March and September. In 2017, the eclipse seasons advance to February and August.
This month’s lunar eclipse is a penumbral eclipse, caused by the moon passing through the penumbral, or partial, shadow of the Earth. An observer on the moon would see the Earth partially covering the sun but not totally covering it.
March’s full Egg Moon will skim through the northern-most edge of Earth’s penumbral shadow before dawn on the morning of March 23, peaking at 5:47 a.m. while low in the western sky. If you rise early that morning, you might notice a slight darkening on the lower half of the full moon, but nothing dramatic.
We’ll have to wait until Jan. 20, 2019, for our next total lunar eclipse, but the real excitement in astronomical circles is for next year’s total eclipse of the sun Aug. 21, 2017.
This will be the first total eclipse of the sun in 38 years to be visible from the U.S. mainland. It won’t be total from Northwest Colorado, but a short trip into Wyoming will put you in the moon’s shadow to see the spectacular total eclipse.
Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College’s Alpine Campus. His “Celestial News” column appears weekly in the Craig Daily Press and his “Cosmic Moment” radio spots can be heard on local radio station KFMU. Check out Westlake’s astrophotography website at jwestlake.com.
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