THE SOUTHWORTH PLANETARIUM
207-780-4249      www.usm.maine.edu/planet
70 Falmouth Street     Portland, Maine 04103
43.6667° N                   70.2667° W
Founded January 1970
Julian date:  2457714.16

            "The one turkey that won't be cooked."







*THE DAILY ASTRONOMER*

*Monday, November 21, 2016*

*Week 12 Night Sky Calendar*





Scorpius the Scorpion is often called the "Thanksgiving Constellation,"
because the Sun appears to pass through it during Thanksgiving.     We know
that Thanksgiving, being the fourth Thursday of November,  can be as early
as November 22nd or as late as November 28th.    The Sun generally enters
the Scorpius region around November 22nd and then departs on or just after
November 29th.   Therefore, if you are settling down for Turkey day with
your nearest, dearest and far too nearest, know that as you're coveting the
moist drumstick, but avoiding all five metric tons of the fruitcake,  the
fearsome scorpion lurks behind the Sun, destined to return to the early
morning winter sky.


*Gobble! Gobble!    **Scorpius the Scorpion** is known*

*as the Thanksgiving constellation because the Sun appears*

*to move through it during this high caloric holiday.*


This week brings us the last quarter moon,  a nearly hidden Mercury-Saturn
appulse, a close lunar encounter with Jupiter, and the moon at apogee.
(Since we devoted so much time to the perigee, we should at least give
passion mention to its polar opposite.)     While this week might not prove
as hyper-kinetic as last week, the sky remains as exquisitely interesting
and indefatigably active as ever.    Welcome to week 12 of
1,989,110,334,115!



*MONDAY, NOVEMBER 21:  LAST QUARTER MOON*


*Last Quarter Moon*

We'll quickly review two LQM facts:
​

First, the last quarter moon rises around midnight.   However, this time is
only an approximation.  The last quarter moon tends to rise earlier than
midnight around the autumnal equinox, but later than midnight around the
spring equinox.    Around the solstices, the last quarter moon rises close
to midnight.


Second, the last quarter moon is slightly dimmer than the first quarter
moon, as the illuminated region we observe at last quarter contains more
darker areas (maria) than that visible during the first quarter moon.


*TUESDAY, NOVEMBER 22:  SUN ENTERS SCORPIUS*

Yes, the Sun' moves into the Scorpius region today.  We won't see anything,
of course, as the Sun will block out the scorpion's stars. The Sun appears
to move into the sky region Scorpius occupies because Earth has moved to
the far side of the Sun relative to these stars. The Sun appears to move
through thirteen constellations each year. These constellations are
SCORPIUS THE SCORPION, Ophiuchus the Serpent Charmer, Sagittarius the
Archer, Capricornus the Seagoat, Aquarius the Water Bearer, Pisces the
Fish, Aries the Ram, Taurus the Bull, Gemini the Twins, Cancer the Crab.
Leo the Lion, Virgo the Maiden, and Libra the Scales. The Sun spends less
time in Scorpius than in any other single constellation. The Sun appears to
move into Ophiuchus on Tuesday,  November 29.


*WEDNESDAY, NOVEMBER 23:  MERCURY 3.4 DEGREES SOUTH OF SATURN*

This one is essentially an academic event, as both planets will be only 15
degrees from the Sun in the western evening sky.  The closest naked-eye
planet to the Sun appears to pass just south of the most distant naked eye
planet.   Mercury, at magnitude -0.5, will appear 2.5 times brighter than
Saturn, magnitude 0.5.    Of course, Mercury has the advantage of
proximity, as it will be about 892 million miles closer to Earth than
Saturn.


*FRIDAY, NOVEMBER 25:   MOON 1.8 DEGREES NNE OF JUPITER (BRONZE EVENT!)*

Jupiter remains the sole eastern pre-dawn naked-eye planet presently.
This morning, one will observe this bright planet close to the waning
crescent moon. (17% illuminated).    Jupiter and the moon will be visible
as the night dissolves into pre-dawn.   Jupiter will vanish about half an
hour before sunrise.


*SUNDAY, NOVEMBER 27: MOON AT APOGEE*

This last week we made a three act opera out of the super moon, defined as
a full moon that occurs when the moon is at or near perigee, the closest
point in its orbit.      The most distant point in the moon's orbit is
called "apogee."   The moon is at apogee today and will be 63.7 Earth radii
from our planet, or about 252,340 miles from Earth.    The moon is only 6%
illuminated and difficult not easy to see, though not because of
its reduced size, but because of its close apparent proximity to the
Sun.



*PLANET WATCH*

*MERCURY (Host constellation:  Libra)*
Mercury is not visible until late November, when it will emerge in the
western evening sky.   Mercury passed into superior solar conjunction on
October 27th.  For three weeks following this conjunction, Mercury will be
too close to the Sun to be visible.     VERDICT:    Don’t bother to search
for Mercury until around Thanksgiving week, when it will high enough in the
west for viewing.  It will return just before Thanksgiving week, but will
be exceedingly difficult to observe.


*VENUS:  (Host constellation:   Ophiuchus)  PICK PLANET!*
As far as brightness is concerned Venus enjoys all the advantages.  Its
pervasive clouds reflect  about 67% of the sunlight it receives. It is
closer to the Sun than Earth, so the incidental sunlight is more intense.
It is also one of the closest planets to Earth, so the reflected light
isn't as diminished as it would be were it farther away.  Also, Venus is
almost as large as Earth, so its reflective surface area is larger than the
other two terrestrial planets, Mars and Mercury.     Venus is often the
pick planet because of these advantages.      Venus remains a bright beacon
in the western evening sky throughout November.    VERDICT:   Easy to see
if one ventures outside soon after sunset.  Venus is one of those celestial
bodies that appears during civil twilight.    Seek it out in the early
evening western sky.


*MARS  (Host constellation:   Sagittarius)*
Careful observers will notice something rather peculiar about Mars.    It
sets around the same time (9:30 p.m.) each night through November, just as
it did for most of October.   This occurs because Earth and Mars are moving
relative to each other in such a way so that Mars' position relative to the
Earth-Sun line remains the same…at least for now.         VERDICT:   Even
though it is nearly 100 times dimmer than Venus, Mars is still a
conspicuous sight in the western evening sky.   It will also remain visible
for about two hours after Venus sets.



*JUPITER (Host constellation:  Virgo)*The second brightest planet, Jupiter
outshines all the night sky stars, but rises in the early morning eastern
sky.     In fact, Jupiter is currently the only visible planet in the
morning sky.    Jupiter rises a few minutes earlier each day and slowly
brightens throughout the year.    VERDICT:   If you're up before dawn,
treat yourself  to some delectable eye candy.    If you'd rather remain in
beautiful communion with your bed, you can wait to see Jupiter at more
decent hours later this winter.



*SATURN  (Host constellation:  Ophiuchus)*We lose Saturn just after mid
month.    One might observe the sixth world low in the southwestern evening
sky during the first three  weeks of November.    Otherwise, it will be
lost to sight.    Saturn passes through superior solar conjunction on December
10th and then will return to the pre-dawn eastern sky by late December.
VERDICT:  Try to find Saturn before November 23rd.  After that, wait until
the end of the year.

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FROM THE CATACOMBS OF INFINITE KNOWLEDGE
*Messier 71: The Globular in Disguise*


*M71:  The "loose" globular cluster located in the *
*Sagitta constellation.     **For two centuries*
*astronomers wondered if it was an open cluster, like the Pleiades*

*or a much larger globular cluster, such as Omega Centauri.  Astronomers
now know M71 is a globular cluster, albeit a loosely*
*bound and comparatively small one.    Image: NASA/HST*
*​*
*​*As our Messier tour continues, we will encounter objects that are not
nearly as prominent as the Orion Nebula (M44) or the Andromeda Galaxy
(M31).   Today's stop takes us to a particularly strange globular cluster
designated as M71.   As is true with many Messier objects, this one was not
discovered by Charles Messier.     It was first observed in 1746  by French
astronomer Philippe Loys de Chéseaux whose instrument was incapable of
revealing its stellar components.     Charles Messier first observed it in
1780 and also classified it as a "nebula with no stars."    Three years
later prolific astronomer William Herschel first resolved this object into
stars.   As it seemed so loosely bound, this cluster was not immediately
recognized as a "globular."  In fact, astronomers debated the character of
this cluster until the 1970's,, when they finally classified M71 as a
globular cluster, as opposed to an open or  galactic cluster.

This globular cluster is 12,000 light years from Earth and has a diameter
stretching 27 light years.    Even with a pair of good binoculars, one can
observe this cluster within the Sagitta constellation.      Search for it
between the constellation's  gamma and delta star:


*Look for M71 in the constellation Sagitta.*
*(Sagitta is tucked inside the Summer Triangle.)*
*One can observe this globular cluster with binoculars,*
*but a telescope is necessary if one wishes to resolve its stars.*


One will need a telescope to observe some of its stars, however.    While
admiring this beautiful, but loose, cluster, realize that you're observing
a globular cluster that is between 9 - 10 billion years old, young by
globular standards.       ​   Even seasoned sky watchers might perceive it
as a rich galactic instead of a loosely bound globular.  However, in
astronomy, as in life, not everything is as it seems.
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