First Spring Full Moon

Looking South tonight at 23:30, EDT from the US Northeast. The Moon is in Virgo and flanked by brilliant Jupiter to the west along the ecliptic and, to the east, by Spica, α Virginis, an evolved helium burning B-class subgiant-giant star. Juxtaposed with the moon are the radiant points for the β and η (Eta) Virginid meteor showers. Image produced with Stellarium. Click for full-res version.

The March full moon is known as the Full Worm Moon, named to mark the time when the ground begins to soften and earthworm casts reappear, inviting the return of robins. Tonight’s full moon also marks the first of four full moons for this Spring. Normally, there are only three full moons for each season, but because of inherent variability and, in no small measure that we’ve had a number of “supermoonsrecently, where the moon is at it’s perigee or closest approach, we will have four this Spring. The moon was it’s perigee two weeks ago on 10 March, so this is a contributing factor. What does that mean for the near future? It means we will be witness to a “Blue Moon” on the third full moon for spring or the full moon for May (21 May). A “Blue Moon” is the occurrence of two full moon phases during one calendar month or the third of four for a given season.

Penumbral lunar eclipse of 28 November, 2012. Image credit: Steve Peter, Delhi, India

Not only is this the first of four full moons for the Spring, a very special “penumbral” lunar eclipse will occur and by the time you get to reading this post, it will have ended. There are two aspects to any eclipse shadow, the umbra and the penumbra. Most lunar eclipses are umbral, in that the moon is full immersed in the earth’s shadow. That is not the case with tonight’s eclipse. At maximum eclipse, occurring in the mid-Pacific and only subtly visible for Asia and most of the North American continent, the moon is never fully immersed in the umbra, the dark, central region of the shadow; hence the term “Penumbral” lunar eclipse. These are quite rare with the previous occurrence back on 28 November, 2012.

Next month’s full moon, occurring on 22 April, will be a “micro” moon when the moon will be at its apogee, or furthest point from the earth in its orbit.

Imagination is more important than knowledge 585px-Albert_Einstein_signature_1934(invert)
An index of all articles in this blog can be found here.


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