THE USM SOUTHWORTH PLANETARIUM
207-780-4249 www.usm.maine.edu/planet
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70 Falmouth Street Portland, Maine 04103
43.6667° N 70.2667° W
Altitude: 10 feet below sea level
Founded January 1970
Julian date: 2458665.5
"Because we're standing on ground that is still shrugging
away the burden of the glacier that melted thousands of years ago;
because, being this close to the ocean, we're within a whisper's distance
of whale song; because we're sailing through the galaxy at half a million
miles an hour; because thousands of souls will draw their first breaths in
the next hour; because we'll never exhaust all the world's possible
harmonies; because the light and heat of a hundred thousand summers not yet
realized now ascends through the turbulent layers of the furious Sun;
because the trillion uniquely intricate snowflakes that have just fallen
will go unobserved; because our supernatural minds contain hundreds of
acres of catacombs not yet explored; because the past is irretrievable, the
future unknowable and the present ungraspable; because arctic ice summits
are cast into lustrous iridescence by auroral light at the same moment
someone sniffs burnt August sand in the tropics; because our misery
precipitates in cleansing tears and our exultations thunder into tectonic
laughter....because of the thousands of other reasons not here mentioned
and the thousands more I haven't even fathomed...am I one of the maudlin,
dim-witted fools who doesn't believe that nothing is a miracle."
THE DAILY ASTRONOMER
Monday, July 1, 2019
July 2019 Night Sky Calendar
The word "month" derives from the word "moonth," the time period
approximately equal to the completion of one lunar cycle: from new moon to
new moon. This actual time period, approximately equal to 29.5 days,
is known as a "synodic month." In July and in August, the new moon
occurs around the first of the month so that the lunar cycle ages as the
month, itself does: new at the beginning, near full in the middle and
almost back to new at month's end. Along the way, the moon will block the
Sun to produce a solar eclipse (we won't see it) and then a fortnight
later, the moon will maneuver into Earth's shadow, creating a partial lunar
eclipse (um, we won't see that event, either.) We will also see the moon
appear to move close to all five visible planets. This month, Earth draws
as far from the Sun as possible, Saturn reaches opposition, and Mercury
moves into inferior conjunction (the last one prior to Mercury's next
transit of the Sun.)
MONDAY, JULY 1: MOON NEAR VENUS (BRONZE EVENT!)
Ordinarily, the close coupling of Venus and the moon would be awarded
silver or even gold status. This time, however, the Moon-Venus appulse
warrants only a bronze medal as both worlds are lurking precariously close
to the Sun in the eastern pre-dawn sky today. The waning crescent moon
(2% illuminated) and our sister planet will both rise just before 4:00 a.m.
By that time, nautical twilight will already be in progress and civil
twilight, that period we call "pre-dawn," will begin less than half an hour
later.
TUESDAY, JULY 2: NEW MOON
WOW!!
Hey, if we were in the southern part of the globe, we'd see a TOTAL SOLAR
ECLIPSE today!
Alas, we're too far north to even see a partial solar eclipse. (However,
we're going to devote tomorrow's DA to this total solar eclipse, anyway, so
we can begin to prepare for the total solar eclipse that we'll see in New
England in 1743 days: April 8, 2024) Today, we'll see nothing: no
eclipse, not even the moon. Lunation cycle 1194 begins!
THURSDAY, JULY 4: MOON NEAR MARS
During this festive holiday commemorating the war of ungrateful Yank
aggression, we can see the thin waxing crescent moon (5% illuminated) close
to the red planet Mars. While Mars is not nearly as bright as Venus, it
remains distinctly reddish and moderately bright. See Mars and the moon
in the western evening sky. Both bodies will set by 10:15 p.m.
THURSDAY, JULY 4: MOON NEAR MERCURY
If you can find Mars and the moon tonight, you can certainly see Mercury,
as well. The three M worlds (a technical term relating to planets with
names starting with M), are gathered together in the western evening sky.
Though it is slightly brighter than Mars, Mercury is a bit more difficult
to observe as it lacks Mars' reddish tint.
THURSDAY, JULY 4: EARTH AT APHELION!
"Aphelion?" That is the point of greatest separation distance between
Earth and the Sun. ("Perihelion" is the point of least distance.)
If Earth's orbit were perfectly circular, the planet's distance from the
Sun would remain constant throughout the year. However, Earth's orbital is
a slightly eccentric ellipse, so its heliocentric distance varies
continuously throughout every orbit. Around July 4th, Earth reaches
aphelion, its greatest distance. Around January 3rd, Earth reaches
perihelion, its least distance. The Sun will be 152.1 million kilometers
(about 94.5 million miles) from Earth today. Around perihelion, the
Sun's distance is 91.5 million miles.
[image: Perihelion-Aphelion.svg.png]
*Aphelion vs. Perihelion: * As Earth travels along a slightly eccentric
elliptical orbit, its distance from the Sun varies from a point of greatest
distance, aphelion, to one of least distance, perihelion. Earth reaches
perihelion in early January and aphelion in early July.
FRIDAY, JULY 5: MERCURY 0.2 DEGREES ENE OF MARS (GOLD EVENT!!!)
Look into the southwestern evening sky tonight and find Mars and Mercury in
close confines. Well, actually, apparently in close confines, as Mercury
will be 61 million miles from Earth today, while Mars will be almost 240
million miles away. Even though these planets are almost of equal
brightness, one can distinguish between them because Mars will appear
crimson, whereas Mercury will simply look white.
TUESDAY, JULY 9: FIRST QUARTER MOON
TUESDAY, JULY 9: SATURN AT OPPOSITION (SILVER EVENT!!)
Today, the swift-footed Earth moves between lethargic Saturn and the Sun.
Were we to observe the solar system from an "aerial viewpoint," we would
see the Sun, Earth and Saturn in a line. Of course, Earth is about eight
times closer to the Sun than it is to Saturn, today. All the same, Saturn
will be at its closest and brightest of 2019 right now! Saturn will rise
around sunset and will remain visible all night.
SATURDAY, JULY 13: MOON NEAR JUPITER
Wait a minute! Why did we specify the angular separation between Mercury
and Mars, but we only mention that the moon will be "near" Jupiter?
Simple: the moon is a fast mover. It shifts its position by half a degree
an hour, equal to its own angular diameter. The moon attains its minimum
angular separation from another body for less than an hour as a
consequence. Whereas, for instance, on July 5th, Mercury and Mars will
remain about 0.2 degrees apart for as long as they remain visible in our
sky that night. On the night of July 13th, we'll see the brilliant
planet Jupiter and the gibbous moon (90% illuminated) close together
throughout the evening. Both of them will remain in the sky most of the
night.
TUESDAY, JULY 16: MOON NEAR SATURN
Up all night! Tonight we'll see the full moon and the sixth planet
appearing to travel together from dusk to dawn. Even though Saturn
reached opposition a week ago it will remain visible nearly all night.
Saturn is easier to see now that at any other time of year owing to its
brightness and duration of visibility. However, finding Saturn is even a
bit easier tonight because it will be the bright "star" close to the full
moon.
TUESDAY, JULY 16: FULL MOON!
And, dang it all to Dixie, today, part of the moon will move into Earth's
shadow, but we here in the eastern arc of the United States will JUST miss
the event. The eclipse will be ending just before moon rise. By this
statement, we mean that the moon will be leaving the penumbra, the outer
part of Earth's shadow, just as it rises. The partial lunar eclipse
will be visible in its entirety in Africa, most of Europe, the Middle East
and many parts of Asia. Even South America will see most of it.
[image: Lunar_eclipse_chart_close-2019Jul16.png]
*Always the Bride's Maid! * On July 14th the full moon will partially
move into the inner part of Earth's shadow, called the "umbra." We here in
the eastern US will miss this event! However, take heart, we will see the
partial lunar eclipse on 21 November 2021!
SUNDAY, JULY 21: MERCURY AT INFERIOR CONJUNCTION
[image: imagfile_0000_0000_0000_2002_0000_0003_0000_0266.png]
When a planet moves between Earth and the Sun, it is said to be in
"inferior conjunction." Mercury passes through inferior conjunction today
and so, won't be visible. However, the next time Mercury goes into
inferior conjunction on November 11, 2019, it WILL be visible as it will
then move directly across the Sun. This Mercurian transit will be entirely
visible here in the eastern US. Hopefully, the sky will be clear, as it
will be the last transit of Mercury we'll see until May 7, 2049!
THURSDAY, JULY 25: LAST QUARTER MOON
SATURDAY, JULY 27: CRESCENT MOON NEAR PLEIADES
Yes, well, the winter stars are returning to the pre-dawn eastern sky, but
we don't have to pay much attention to them, at least not now. Venture
out to observe the sky in the wee hours and you'll see the waning crescent
moon (26% illuminated) close to the Pleiades. The moon won't be bright
enough to totally obscure the Pleiades Star Cluster
PLANET WATCH
MERCURY is visible in the western evening sky during the early part of
July. However, by mid month, the first world will be too close to the
setting Sun to be observable. VERDICT: Try to find Mercury in early
July. Seek out Mercury on July 5th when it will be close to Mars!
VENUS. July is not a favorable month for Venus. The bright planet begins
the month very low in the eastern pre-dawn sky. By the second week, Venus
vanishes! However, our sister world will return to the western evening sky
in September and will become a brilliant autumn sky beacon. VERDICT:
Yeah, well, ok, you can try to find Venus if you're out before sunrise in
early July. Otherwise, wait until September to find Venus in the evening
sky.
MARS is dimmer than it was this time last summer. The fourth world will
vanish into the western dusk by mid month. Mars will then be on hiatus
until late October, when it returns to the morning sky. VERDICT: Like
Venus, Mars is best seen early in the month. By mid month, Mars will then
be out of sight until almost mid autumn
JUPITER is big, bright, and up for most of the night. Jupiter was at
opposition on June 10th and now begins the evening in the eastern pre-dawn
sky. The behemoth planet remains visible until the onset of early
twilight. VERDICT: Owing to its brilliance and position, Jupiter is
quite easy to find throughout July. Seek it in the evening and even well
after midnight.
SATURN (PICK PLANET!) Saturn isn't as bright as Jupiter, but as it passes
into opposition this month, this planet is designated as the month's pick
planet! VERDICT: See Saturn at any time of night! Up around sunset
and down by sunrise.