Eclipse across the Andes (and Washington)

The Moon wields a wand: the long slender shadow called the umbra, which when it touches Earth creates a magic show.  The wand will sweep across South America on December 14.

See the end note about enlarging illustrations.

The viewpoint of this picture is 12 Earth-radii from the Earth’s center.  So the Moon is about 5 times farther back, along the shadow which it casts, and the Sun is about 400 times farther than that.  The large gray patch, faintest at its outer edge, is the footprint of the penumbra, or partial shadow, at the time of the picture.  Curves show the outlines of the penumbra and umbra at the Universal Times marked.  Arrows show the flight of Earth along its orbit in 1 minute, the flight of the umbra in 1 hour, and, on the equator, the rotation of Earth in 1 hour.  In the background are stars of the western end of Gemini.

Here’s a close-up pf that picture, showing the path of totality across mid-southern Chile and Argentina:

The eclipse happens because the Moon (by which we mean its center) descends southward through the ecliptic plane on Dec. 14 at 11 Universal Time, only about 2 hours before passing between us and the Sun, at its New Moon moment.

This year has 6 eclipses (the usual number is 4; less common are 5, 6, or even 7).

Jan. 10: lunar, penumbral
June  5: lunar, penumbral
June 21: solar, annulat
July  5: lunar, penumbral
Nov. 30: lunar penumbral
Dec. 14: SOLAR, TOTAL

The lunar eclipses were all penumbral, that is, slight, because near the fringes of their eclipse seasons.  (The January one was the last of an eclipse season starting in 2019.)  The middles of the other two eclipse seasons (that is, the moments when eclipses, if they happened, would be exactly central) were on June 20 and Dec. 11.  So you can see that the June 21 eclipse was nearly central (but the Moon was too distant to cause a total eclipse) and the Dec. 14 one is a little less central.

The eclipse seasons are displayed in the “bead curtain” chart in our book The Under-Standing of Eclipses; here is a fraction of one of the 12 pages covered by that chart:

(Each year reads from right to left because the Moon moves eastward.  The small circles are the New or Full Moon dates at which eclipses do not happen.)

This was the penumbral eclipse of the Moon on Nov. 30:

If you have the luck to be in South America, I hope the eclipse offers you as majestic a show as we had in South Carolina on 2017 August 21.  Take another look at those pictures.

Some more about the eclipse tomorrow, I hope.

Eclipsed demagogues department

So Donald Lame-Duck was defeated,
So he had to pretend he was cheated.
With evidence lacking
He never stopped quacking
But lies are still lies when repeated.

Truculent Trump rose into view as the “star” of a reality show, in which he delighted to growl “You’re fired!” at candidates for jobs.  He now, having been fired himself, seems to be the star of an unreality show.

__________

ILLUSTRATIONS in these posts are made with precision but have to be inserted in another format.  You may be able to enlarge them on your monitor.  One way: right-click, and choose “View image”, then enlarge.  Or choose “Copy image”, then put it on your desktop, then open it.  On an iPad or phone, use the finger gesture that enlarges (spreading with two fingers, or tapping and dragging with three fingers).  Other methods have been suggested, such as dragging the image to the desktop and opening it in other ways.

Sometimes I make improvements or corrections to a post after piblishing  it.  If you click on the title, rather than on ‘Read more’, I think you are sure to see the latest version.

This weblog maintains its right to be about astronomy or anything under the sun.