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September 2017 Skies

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September Skies

by Dick Cookman



Highlights: Comet Journal, Martian Landers, Meteor Showers, Autumnal Equinox, Planet Plotting, September Moon

Focus Constellations: Perseus, Cassiopeia, Andromeda, Pegasus, Cygnus, Lyra, Aquila, Ophiuchus, Hercules, Draco, Cepheus, Ursa Minor, Ursa Major, Camelopardalis

Comet Journal

Comet C/2017 O1 is in Taurus in September. It is at 8th magnitude and may reach 7th magnitude and remain that bright through November. C2015 ER61 (PanSTARRS) is also in Taurus and has dimmed to 10th magnitude as it retreats from the inner solar system.

Mars Landers

Opportunity is at "Perseverance Valley” on the western rim of "Endeavor Crater", the 14 mile wide crater located on "Meridiani Planum", the plain where the rover landed in January of 2004. Opportunity emerged from solar conjunction in late July after experiencing a warm reset on Sol 4795 (July 20, 2017) which stopped all sequencing and put the rover in a safe state called automode.

Recovery action ensued after the solar conjunction communication blackout period ended. One sol before the official conclusion of conjunction on Sol 4807 (August 1, 2017), successful real-time commands were sent to the rover restoring master sequence control allowing Opportunity to resume normal operations. After conducting extensive imaging to determine the nature of the valley and to examine potential locations for spending the oncoming winter season, Opportunity drove for the first time since conjunction on Sol 4813 (August 7, 2017). During the next 3 weeks, the drive from one energy-favorable "lily pad" to the next tested locations with terrain sufficiently tilted to the north to maximize solar illumination on the rover's solar panels.

As of Sol 4834 (Aug. 29, 2017), the rover reached total travel on Mars of 27.97 miles (45.02 kilometers). Solar array energy production averaged 305 watt-hours per sol during the month.

Examination of Martian rocks and sediments in a former lake bed in Gale Crater by Curiosity, the Science Lab rover revealed numerous simple organic molecules. On Earth, chains of these molecules form cell walls and other organic structures. Although Mars is now cold and dry, Curiosity also examined samples with abundant evidence of much warmer and wetter conditions. In addition, unusually high ratios of heavy isotopes of elements in the Martian atmosphere indicate that lighter isotopes once present in the atmosphere may have been lost to space, a circumstance thought to result from bombardment by solar winds after Mars lost its protective magnetic field. As the rover ventures higher in its ascent of Mt. Sharp, younger rocks dominated by hematite, clay, and sulfate may record details of the transition to cold and dry conditions.

Meteor Showers

The minor Meteor Showers of September include the Alpha Aurigids which peak at about 5 meteors per hour in dark skies on the 1st, the Delta Aurigids which start in mid-September and peak in early October, and the Epsilon Perseids which peak on the 9th. The Alpha Aurigid shower is typically the best but is competing with the gibbous Moon this year which sets around midnight leaving a sky free of lunar glare to observe the meteors when Auriga is higher in the sky. Comet Kiess (C/1911 N1) is the source of the material that causes the meteors. The Epsilon Perseids will have to deal with the waning gibbous Moon throughout the night.

Autumnal Equinox

One month and one day after the 1st total Solar Eclipse to cross the entire USA since 1919, the Earth arrives at one of the two locations in its orbit where our axis is perpendicular to a line between Earth and Sun. The axis is also tipped toward the direction of orbital travel on the Sept. 22nd equinox at 4:02 PM EDT, marking the start of the autumn season and presaging the winter season in the northern hemisphere when the axis is tipped away from the Sun on the December solstice.

Fortunately, Earth is approaching perihelion on the solstice. It will be closest to the Sun in early January when warming rays make northern hemisphere winter less drastic than if we had to struggle with winter at aphelion like those poor folks in the southern hemisphere. To their benefit, southern hemisphere climate is moderated by large southern hemisphere water bodies which dominate minimal areas of southern hemisphere continents.

Both hemispheres share equal periods of light and darkness at the equinoxes when the main variance in solar intensity is related to latitude. Polar regions receive glancing tangential rays from a Sun barely above the horizon and equatorial regions bask in the direct rays of a high altitude Sun.

Planet Plotting

Morning planets include Venus (-3.9 to -3.8) in Cancer and Leo. Mars (+1.8) is in Leo in September. Mercury (3.7 to -1.3) is in Leo and Virgo, Uranus (+5.7) is in Pisces, and Neptune (+7.8) is in Aquarius.

Mercury gets brighter throughout September as it approaches Superior Conjunction in early October. It is over 10° from the Sun on the 1st, increases to 17.9 at maximum western elongation on the 12th, then decreases to 6° on the 30th. Venus rises before 5:00AM EDT and is still above the horizon at sunrise. Mercury and Mars are in close proximity during the first half of the month and Venus joins in at mid-month after which the waning crescent Moon passes close to each. Uranus and Neptune rise in the evening and are in the southwestern sky before dawn. Both are near the Full Moon in early September.

Jupiter (-1.6 to -1.5) in Virgo and Saturn (+0.4 to +0.5) in Ophiuchus rise during the day and set in the evening. Jupiter is falling into the glow of sunset and will be lost from sight as it approaches conjunction with the Sun in late October. The waxing crescent Moon passes Jupiter on the 22nd and Saturn on the 26th.

PlanetConstellation(s)MagnitudePlanet PassagesTimeDate
SunLeo, Virgo-26.8New Moon1:30AM EDT9/20
MercuryLeo, Virgo+3.7 to -1.3Mars 3.2° NE
Max West Elongation
Venus 10.9° WNW
Mars 0.06° SSW
8:00PM EDT
6:00AM EDT
8:00AM EDT
3:00PM EDT
VenusCancer, Leo-3.8Mercury 10.9° ESE8:00AM EDT9/14
MarsLeo+1.8Mercury 3.2° SW
Mercury 0.06° NNE
8:00PM EDT
3:00PM EDT
JupiterVirgo-1.6 to -1.5   
SaturnOphiuchus+0.4 to +0.5   
NeptuneAquarius+7.8Opposition1:00AM EDT9/5

September Moon

The September New Moon is on the 20th at 1:30AM EDT. It is the beginning of Lunation 1172 which ends 29.57 days later with the New Moon of Oct. 19th at 3:12PM EDT.

The Full Moon of September in Aquarius occurs at 3:04AM EDT on the 6th. It is called the “Fruit Moon”. Colonial Americans called it the “Harvest Moon” which is defined as the full moon closest to the equinox or the first full moon following the equinox. September’s Full Moon is the Harvest Moon by the first definition and the second definition places it in October in 2017. To the Celts it was the “Singing Moon”, and Chinese refer to it as “Chrysanthemum Moon”. It was the “Barley Moon” in Medieval England. Anishinaabe (Odawa and Ojibwe) people in northern Michigan recognize it as “Waatebagaa-giizis" (Leaves Turning Moon).

Lunar Perigee (closest to Earth) is 229,820 miles or 57.99 Earth radii on the 13th at 12:11PM EDT. Apogee (maximum orbital distance) occurs on the 27th at 3AM EDT when it is at 251,250 miles (63.40 Earth radii).

PlanetConstellationMagnitudeMoon PassageMoon PhaseMoon Age
SunVirgo.-26.81:30AM EDT 9/20New0 days
MercurySextans-0.90.05°SE, 7:00PM EDT, 9/18Waning Crescent28.19 days
VenusGemini-3.80.53°SSW, 9:00 PM EDT, 9/17Waning Crescent27.27 days
MarsLeo+1.80.17°NE, 4:00PM EDT, 9/18Waning Crescent28.06 days
JupiterVirgo-1.53.5°NNE, 6:00AM EDT, 9/22Waxing Crescent.2.19 days
SaturnOphiuchus.+0.53.5°N, 9:00PM EDT, 9/26Waxing Crescent6.81 days
UranusPisces+5.74.1°SSE, 9:00AM EDT, 9/9Waning Gibbous18.77 days
NeptuneAquarius+7.80.74°SSE, 1:00AM EDT, 9/6Waxing Gibbous15.44 days

  • GalacticS likes this


Excellent read, thanks for posting and sharing.  SkySafri has that Comet at +12.9 but I may have to update the data.

(Did the data update and still shows comet as mag +12.9?)

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