THE SOUTHWORTH PLANETARIUM
70 Falmouth Street Portland,Maine 04103
(207) 780-4249 usm.maine.edu/planet
43.6667° N 70.2667° W Altitude: 10 feet below sea level Founded
January 1970
2021-2022: XXV
"If it's a psychic network, why do they need a phone number?" -Robin
Williams
THE DAILY ASTRONOMER
Thursday, October 7, 2021
October 2021 Night Sky Calendar Part III
*WEDNESDAY, OCTOBER 20: FULL MOON*
The Hunter's Moon!
The Hunter's Moon immediately follows the Harvest Moon, defined as the full
moon which is closest to the autumnal equinox. As the Harvest Moon can
happen in either September or October, the Hunter's Moon will only occur in
October or November. The Harvest Moon is so named because the full moon's
light illuminates the crop fields all night long, allowing the hard-working
farmers ample time to pick their crops. The Hunter's moon casts silvered
light onto the forests and meadows to aid the hunters in their quest for
quarry. (One would think that this light might help the prey animals, as
well.)
*THURSDAY, OCTOBER 21: ORIONID METEOR SHOWER PEAKS (GOLD EVENT!!!)*
Let's talk about THIS meteor shower, one of the year's most prominent
meteor events. Our discussion begins with the famous Halley's Comet. Some
subscribers might recall this comet's last visitation in the mid 1980's.
(For many observers, the actual appearance didn't live up to the
20-needles' worth of pre-arrival hype.) Ever since this icy interloper
swooped around the Sun, it has been traveling at progressively slower
speeds toward the outer solar system. (In December 2023, Halley's Comet
will reach aphelion and then turn around for the prolonged journey back
toward the inner solar system.) Like all active comets, when Halley's Comet
ventures close to the Sun, it forms two tails: an *ion tail* consisting of
charged particles repelled by the solar wind and a *dust tail* that forms
when the particles trapped within the comet's surface are liberated by the
sublimating ices*. Those particles create the meteors we observe.
Each year, Earth moves through the particle cloud that formed in Comet
Halley's wake. These particles, properly called *meteoroids*, infiltrate
the atmosphere at high speeds. The descending meteoroid moves so quickly
that it compresses the air along its path. The resultant heating excites
the atoms surrounding the meteoroid. When *excited,* electrons within the
atoms absorb energy and rise to higher energy levels. The excited electrons
quickly return to their original energy states and release light photons.
That light produces the meteors we observe.
The Orion Meteor shower, so named because the meteors appear to emanate
from a region within the constellation Orion, began on October 2 and ends
on November 7th. It peaks today, meaning that today Earth will pass through
the densest part of the meteoroid stream. We can expect 20 - 30 meteors an
hour.
The best time to observe these meteors is after midnight, the time when our
part of the planet is turning into the meteoroid stream.
This year's Orionid shower might not appear so spectacular due to the lunar
light interference as the waning gibbous moon will remain in the sky
throughout most of the night.
*SATURDAY, OCTOBER 23: MOON NEAR PLEIADES*
The waning gibbous moon (93% illuminated) glides by the Pleiades Star
Cluster this evening. Despite the considerable lunar light interference,
observers should still be able to see this gorgeous star cluster, known as
the "seven sisters," in reference to the number of stars visible to the
unaided eye.
[image: pleiades-seven-sisters-nov2019-e1572962425736.jpg]
The Pleiades Star Cluster as seen in a time exposure image.
The splotches of gas surrounding the star are all part of the Maia Nebula,
a gaseous "cloud" through which the cluster is currently moving. The stars
illuminate this nebula like fireflies in a fogbank. The Maia Nebula is
classified as a "reflection nebula," or one that is rendered visible by the
light of embedded stars.
*MONDAY, OCTOBER 25: MERCURY AT GREATEST WESTERN ELONGATION*
Just a quick review:
-when a planet is at greatest western elongation, it will be
visible in the eastern pre-dawn sky.
-when a planet is at greatest eastern elongation, it will be
visible in the western evening sky.
One will find Mercury in the early morning. In fact, this is the best
time of month to find the first world. (See "Planet Watch.")
*THURSDAY, OCTOBER 28: VENUS AT DICHOTOMY*
Venus at what?
Venus at Dichotomy, or, if you want less obfuscation, theoretical
dichotomy. Or, if you prefer the type of English that is served with
cookies instead of crumpets, Venus is half lit up.
[image: 31309995353_1d79fdc099_z.jpg]
Venus at dichotomy or half illumination
Galileo knew his soul was imperiled when he first viewed Venus through a
telescope and observed its phases. That observation provided compelling
evidence in support of the Sun-centered (heliocentric) as opposed to the
Earth-centered (geocentric) model that the empowered elite preferred.
Provided you hold your soul light, you can observe Venus' phases yourself
through any telescope. Look at it today and you'd see a "half Venus."
Like the moon, the two inferior planets exhibit a phase cycle.
Although, as neither Mercury nor Venus is ever on the far side of Earth
relative to the Sun, neither one will ever appear "full." Today, Venus
is just in the right position relative to the Earth and Sun to be
half-lit. One won't actually notice this phase until one observes Venus
telescopically. To the unaided eye, Venus appears as a brilliant dot in
the western evening sky.
*THURSDAY, OCTOBER 28: LAST QUARTER MOON*
Hey, the moon is also at theoretical dichotomy, or half illuminated.
*FRIDAY, OCTOBER 29: VENUS AT GREATEST EASTERN ELONGATION*
Remember what we said earlier about Mercury's greatest western elongation?
If the elongation is western, the planet's in the easten sky and if it is
an eastern elongation, the plane is in the west?
Well, Venus is the brilliant beacon in the western evening sky tonight!
At this elongation, it will be 47 degrees from the Sun, its maximum
possible elongation.
A great time to observe Venus!
*SUNDAY, OCTOBER 31: HALLOWEEN/SAMHAIN*
Perhaps the best known Cross-quarter day, or day midway between successive
seasonal points (an equinox or solstice or a solstice and equinox).
Halloween, or Samhain (the Pagan New Year) marks the midpoint between the
autumnal equinox and winter solstice. We've reached mid-autumn!
The other cross-quarter days:
-Groundhog's Day/Imbolc Feb 2
-May Day/Beltane May 1
-Lammas August 1
*PLANET WATCH*
*MERCURY*
Mercury needs a heaping dose of the ADHD drug Ritalin. This elusive,
sun-hugging world completes an orbit every 88 Earth days. Consequently, it
vacillates so rapidly between horizons that one finds it exceedingly
difficult to keep track of it. At the beginning of the month, Mercury will
not be visible owing to its close proximity to the Sun. Toward the
middle of October, Mercury juts up low in the eastern pre-dawn sky and
remains visible the rest of the month. *VERDICT:* Mercury seeking is
not for the faint-hearted. However, Mercury admirers are advised to
venture out toward the end of the month, around the time Mercury reaches
greatest western elongation (October 25th).
*VENUS*
Although Venus reaches greatest eastern elongation toward the end of the
month, it is not in a favorable position for us northern hemisphere
observers. It seems grotesquely unfair that the southern hemisphere gets
spring, a better view of Venus AND Hobbiton. Despite its low angle,
Venus will be easy to find immediately after sunset. As always, Venus
outshines all the night sky objects apart from the moon. VERDICT: Seek
out Venus during or just after dusk. Though stunningly bright, it won't
loiter above the horizon for much of the night.
*MARS:*
Is not visible this month.
The red world is moving behind the Sun and won't be visible again until the
very end of the year. Mars watchers should find other fixations until
next year when the fourth world slowly rises back into prominence.
*JUPITER (PICK PLANET)*
Yes, Jupiter gets the coveted pick planet distinction again! Venus is
brighter, but more difficult to observe. Jupiter outshines all the
night sky stars (well, not put together) and will remain visible well after
midnight. The giant planet begins the night high in the eastern sky, a
perfect object for even the type of half-hearted sky watcher who only
indulges in astronomy during interminable commercial breaks. *VERDICT:
*Go out after darkness descends and see Jupiter high in the eastern sky.
Jove shall remain the beacon of the autumn night sky.
*SATURN*
The best way to find Saturn is to first locate Jupiter. Saturn will be
an extended "fist's width" to the northwest. We advise you to first
find Jupiter because it will be 17 times brighter than its gas giant
cohort. VERDICT: If you're looking at Jupiter , anyway, you might
as well sneak a peek at Saturn. Although you can't see the rings, Saturn
will still be a pleasing sight to the eye: a moderately-bright planet
nearly one billion miles from Earth.
*"sublimates" means that the ice turns directly into vapor without passing
through the intermediate liquid stage.
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