THE USM SOUTHWORTH PLANETARIUM
207-780-4249     www.usm.maine.edu/planet
<http://www.google.com/url?q=http%3A%2F%2Fwww.usm.maine.edu%2Fplanet&sa=D&sntz=1&usg=AFQjCNHulkHuLP13bOG2PkNrPazsGWFs2A>
70 Falmouth Street     Portland, Maine  04103
43.6667° N                   70.2667° W
Altitude:   10 feet below sea level
Founded January 1970
Julian date:  2458666.5
                           'Nothing, absolutely nothing is as effective in
human communication  and expression, as  pithiness and conciseness  in
speech, phrasing, and syntax."

THE DAILY ASTRONOMER
Tuesday, July 2, 2019
The Solar Eclipse We Won't Observe


Wait a second!
We have often said when the moon moves directly in front of the Sun, we'll
experience a solar eclipse.   Today, the moon will move directly in front
of the Sun and we here in the great northern climes will see, well, the Sun
as we generally see it every day!    Even when the eclipse is at totality,
the Sun will adorn our skies san shadow.

How can that possibly make any sense?

It is all  matter of geometry.     Refer to the below graphic:

[image: earth_moon_scale.jpg]

The moon's shadow cone tapers down as it moves away from the moon, itself.
By the time the shadow cone intersects with Earth, it will cover a
relatively small area.    Only those observers who are standing inside that
area, called the "umbra," will observe a total solar eclipse.   As Earth is
rotating (and the moon is orbiting) during the moon's passage across the
Sun, a narrow path will be drawn across Earth.  (Think of pressing a very
small, wet paintbrush against a slowly turning globe.   The resultant arc
will be similar in shape to this totality path.)  Observers to the north or
south of this path will observe a partial solar eclipse, the magnitude of
which decreases with increasing distance from the totality patj.
Observers who are seeing a partial solar eclipse are standing in the path
of the moon''s outer shadow, called the "penumbra."   In the image above,
the penumbra is depicted as the wider gray triangles above and below the
thinner dark umbra.  This image provides a scale model of the Earth/moon
system, giving us an idea of the real distances involved.

Observers outside the penumbra will see no partial eclipse at all.  The Sun
will appear unblocked!       The map below shows the eclipse path.   The
blue arc represents the totality path.  The grid to either side of it
represents the region where only a partial solar eclipse will be visible.
 For instance, an observer along the 0.60 arc will notice an eclipse of 0.6
magnitude:  the moon will cover 60% of the Sun's diameter.   We can see
that every region in the United States is well north of the upper eclipse
limit.    We'll enjoy a sunny day (in theory) without any lunar
obstruction.

[image: SE2019Jul02T.png]
*The eclipse grid:*    observers along the blue arc will observe a total
solar eclipse.  Observers along the grid outside the totality path will see
a partial solar eclipse.     Those observers outside the grid will be
beyond the penumbra and won't observe any eclipse at all.


Again, take heart,  we here in New England will experience a total solar
eclipse on April 8, 2024!