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: 2457665.16
"!yad sdrawkcab yppaH"
*THE DAILY ASTRONOMER*
*Monday, October 3, 2016*
*Week 5 Night Sky Calendar*
*October 3 - 9, 2016*
First full week of October: the month that ends the year for some and
begins the holiday season for others. October is the month during which the
summer-lovers who are mired in the denial's enveloping depths are wrested
back into reality's chilled breezes. We proceed despite the sudden
onset of reality. This week's night sky calendar turns out to be wholly
moon based, as we watch the waxing crescent moon swing by some planets in
the western evening sky. Of course, we'll include the planet watch
section and we'll also visit the catacombs of infinite knowledge.
Note: a few subscriber's asked us to give out medals again, as we did when
we posted the monthly sky calendars. For those who are now scratching
their heads, we once assigned medals -Bronze, Silver, Gold and on rare
occasions Platinum- to the events we deemed the most important. We
conferred the gold (or occasionally platinum) onto the event we considered
the true highlight. The second most important received silver, the third
most important, bronze. We abandoned this scheme in September, but will
now re-introduce it in October. That announcement brings us neatly to
this week's first event:
MONDAY, OCTOBER 3: MOON 4.9 DEGREES NNE OF VENUS (SILVER EVENT!!)
The thin crescent moon lingers close to Venus in the western evening sky.
This coupling is always one of the most beautiful night sky sights. We
see a brilliant planet next to a crescent moon. Venus is a crescent, too,
even though we can't see the crescent with just the unaided eye. (See
"From the Catacombs of Infinite Knowledge.") The moon will be 7%
illuminated tonight and will set just before 8:00 p.m.
THURSDAY, OCTOBER 6: MOON 3.8 DEGREES N OF SATURN
Tonight, we'll see the larger crescent moon just north of Saturn, the sixth
planet from the Sun. The moon will be 27% illuminated and will set
before 10:00
p.m. One might wonder why the moon tends to veer close to planets as
it moves through the sky. The reason is simple. The planets and the
moon both travel within a band centered on the "ecliptic," the Sun's
apparent annual path through the sky. These worlds are restricted to
this region because the solar system is disc-shaped and will remain very
close to its "invariable plane." A planet can move below or above the
ecliptic by a certain number of degrees determined by its inclination
relative to the ecliptic. (For instance, Saturn's inclination is
approximately 2.5 degrees, so it can be as much as 2.5 degrees south or 2.5
degrees north of the ecliptic.) The moon has a slightly greater degree of
freedom, as its inclination is approximately 5 degrees.
*The Ecliptic Band**. The planets and moon travel along a band centered on
the ecliptic, the Sun's apparent annual path through the sky. The
moon's inclination relative to the ecliptic is about 5 degrees, so it
doesn’t' stray far from it. The planets also travel close to the ecliptic
because the solar system is disc shaped and the planets move close to the
solar system's "plane." Image by Astrobob [IMPORTANT: this chart does not
show the current configuration of planets!]*
SATURDAY, OCTOBER 8: MOON 7.0 DEGREES N OF MARS
The third lunar-planet encounter of the week brings the moon close to
Mars. One can easily mistake tonight's crescent moon for the quarter
moon, as it will be 45% illuminated. This week the moon will prove a
helpful guide to finding Mars and Saturn, which are almost equally bright
and much dimmer than Venus!
SUNDAY, OCTOBER 9: FIRST QUARTER MOON
PLANET WATCH
MERCURY (Host constellation: Virgo)
Mercury is only visible early in October and then vanishes for the rest of
the month. Even when visible, Mercury is low in the pre-dawn eastern
sky. Mercury passes into superior solar conjunction on October 27th and
won't return to the evening sky until late November. VERDICT: Even by
Mercury's standards, it is not an easy planet to find this month. If you
must try, do so at the very beginning of October. Otherwise, wait until
around Thanksgiving. Yes, it will be that long of a wait.
VENUS (Host constellation: Libra/Scorpius) PICK PLANET!
Venus gets the crown again because it is so bright, even if it doesn't
remain in the western evening sky for long. Venus brightens only
slightly throughout the month, but, as always, is brighter than any night
sky star. VERDICT: It will be easy to find Venus provided you venture
outside in the early evening. Look to the west and see the brilliant
Venus. Best day to look this week will be October 3, when Venus will be
close to the moon
MARS (Host constellation: Sagittarius)
Though it is not as bright as Venus, Mars is easy to find in the western
evening sky. Interesting note: Mars will be setting around 9:30 p.m. each
night throughout the month. This equivalence occurs because of the way
Earth and Mars are moving relative to each other at the moment.
VERDICT: Seek out the red world in the evening this month. It will
remain above the horizon for a couple hours after sunset.
JUPITER (Host constellation: Virgo)
After a month-long hiatus, Jupiter retrurns to the early morning eastern
sky. Consider this to be a perfect "changing of the guard." As Mercury
vanishes in the pre-dawn twilight, Jupiter emerges. Though not as
bright as Venus, Jupiter shines brighter than any night sky star. VERDICT:
If you've dearly missed Jupiter, just venture outside to find it starting
mid-month. Jupiter will brighten throughout the rest of 2016 as it rises
earlier each morning.
SATURN (Host constellation: Libra)
We'll lose Saturn next month. In October, Saturn lurks low in the
southwestern evening sky. It is still a moderately bright planet and will
be easy to find, at least early in October. VERDICT: Seek out Saturn at
month's beginning just after dark. Still a beautiful world,
particularly through a telescope. Although we lose Saturn in November,
we'll regain it in late December.
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FROM THE CATACOMBS OF INFINITE KNOWLEDGE
*"Phases of Venus"*
Have you ever observed Venus through a telescope? If not, it might be
surprising to know that when viewed telescopically, Venus will most likely
appear as a crescent or, on occasion, as a quarter. Venus exhibits a
phase cycle, just as the moon does. However, we'll never see a "full
Venus," because the planet can never be farther from the Sun than Earth.
*Phases of Venus: **Venus exhibits a phase cycle similar*
*to that of the moon. However, we'll never see a "Full Venus"*
*because it will never be farther from the Sun than Earth.*
*Image: T. Lombry*
Venus and Mercury both have a phase cycle because they are both inferior
planets, or closer to the Sun than Earth. Unlike Venus, Mercury will
never appear as quarter, but will always be a crescent as it can never be
farther than 28 degrees from the Sun in our sky.
Galileo's observation of the crescent Venus lend credence to his belief
that the Sun, not Earth, occupied the center of the solar system. Were
Venus to have revolved around Earth, it would have appeared full every so
often. It never did.
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*From a hidden chest within the catacombs of infinite knowledge*
The term for a quarter Venus is the very catchy
Theoretical Dichotomy
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