Universe Today
Ready for Easter? The
first of two lunar eclipses
for 2016 occurs this week, though it's an event so subtle, you might not notice it at first glance. We're talking about Wednesday evening's (morning for North America) penumbral lunar eclipse. If a
total solar eclipse
such as the one that crossed Indonesia and the Pacific Ocean earlier this month is the ultimate astronomical experience, then a penumbral lunar eclipse is at the other end of the spectrum, a ghostly shading on the Moon that is barely noticeable.
[caption id="attachment_127986" align="alignnone" width="580"]
The path of the Moon through the Earth's shadow Wednesday. Adapted from
NASA/GSFC/Fred Espenak
[/caption]
Circumstances: A penumbral eclipse occurs when the Moon just grazes the outer faint shadow of the Earth, missing its dark inner core known as the umbra, as occurs during a total lunar eclipse. Standing on the Earthward-facing side of the surface of the Moon this Wednesday, you'd see a partial solar eclipse looking back at the Earth.
[caption id="attachment_127987" align="alignnone" width="580"]
Looking west on Wednesday morning before moonset. Image credit: Stellarium[/caption]
The penumbral eclipse begins at 9:39 Universal Time (UT) on Wednesday, March 23
rd
, reaches its peak at 11:48 UT with the Moon 78% immersed in the Earth's penumbral shadow, and ends on 13:55 UT. The eclipse occurs during moonrise for Far East Asia Wednesday night, and moonset for the Americas on the morning of Wednesday, March 23
rd
. The central Pacific will witness the entire eclipse crossing the International Dateline, with the Moon high overhead for observers in Hawaii.
[caption id="attachment_127988" align="alignnone" width="580"]
Visibility for this week's penumbral lunar eclipse.
- Image credit
-
NASA/GSFC/Fred Espenak[/caption]
Tales of Saros
This particular eclipse is part of
saros 142
, and is number 18 of 74 in the series, which began on September 19
th
, 1709. Stick around until July 22
nd
2214, and you can witness the very first total lunar eclipse of saros 142, which runs out to November 4
th
, 2989. If you saw the penumbral lunar eclipse of
March 13th, 1998
which was visible from most of North America, then you caught the last lunar eclipse of the series.
As does every lunar eclipse by necessity, this week's event falls on the Full Moon. The March Full Moon is known as a
Worm Moon
, and in 2016 is also the
Paschal or first Full Moon
after the vernal equinox setting us up for Easter this weekend. On the Gregorian calendar, the rule for Easter is the 'first Sunday after the first Full Moon after the fixed date of March 21st for the vernal equinox,' though an equinox won't fall on March 21st again until 2102 AD. This is because of another rule from the Gregorian calendar, the skipping of century leap years except on years (such as 2000) divisible by 400, resets the date... all in a never-ending effort to keep sidereal and mean solar time in sync.
By coincidence, the Moon also occults (passes in front of) the +3.9 magnitude star
Eta Virginis
during the eclipse for observers in southeast Asia. Thanks to Malaysian-based observer Sharin Ahmad (@shahgazer on Twitter) for pointing this out to us.
[caption id="attachment_127989" align="alignnone" width="580"]
The visibility footprint for the occultation of Eta Virginis. Image credit: Occult 4.2[/caption]
So, what is there to see during a penumbral eclipse? Well, you might just notice a slight tea-colored shading on the lower southern limb of the Moon right around greatest eclipse. Make the judgment call: would you notice a penumbral eclipse at all if you didn't know one was underway? The higher in the sky the Moon is, the better, as a low elevation Moon tends to become tinted via atmospheric refraction.
Here's a photographic challenge: keeping all of your camera settings the same, image the Moon before during and after the eclipse... can you see the difference? A penumbral eclipse would be worthy of a short animation as well.
[caption id="attachment_127990" align="alignnone" width="368"]
An image comparison of the Moon before (left) and during (right) a penumbral lunar eclipse. Image credit: David Dickinson[/caption]
When is the next total lunar eclipse? Well, we've got another penumbral on September 16th of his year, but the next total lunar doesn't occur until January 31
st
, 2018, again favoring the Pacific and western North America.
Oh well. We can always reminiscence of the lunar eclipse tetrad of past years. Let us know if you catch sight of this week's penumbral eclipse.
...and while you're out under (hopefully) clear March skies don't miss Jupiter at its prime... and just maybe, binocular
Comet 252P LINEAR
, making its appearance for northern hemisphere observers this weekend as it flies through the constellation Scorpius in the pre-dawn.
-Be sure to send those pictures in to
!