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August 2018 Skies

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August Skies

by Dick Cookman


Highlights: Comet Journal, Martian Landers, Meteor Showers, Planet Plotting, August Moon

Focus Constellations: Coma Berenices, Bootes, Corona Borealis, Hercules, Ophiuchus, Aquila, Lyra, Cygnus, Cepheus, Draco, Ursa Major, Ursa Minor, Cassiopeia, Andromeda, Pegasus

Comet Journal

C/2016 S3 (PanSTARRS) was on course to reach naked eye visibility when closest to Earth on August 7th and near perihelion on the 16th. Unfortunately it chose to disintegrate on July 27th when, like Icarus, the son of Daedalus, despite the admonishments of his father, it too flew too close to the Sun. LISTEN TO YOUR FATHER, HE KNOWS MORE ABOUT LIFE THAN YOU DO, AND, HE COMPLIES WITH YOUR MOTHER'S WISHES!!

21P/Giacobini-Zinner (2018), which moves through Cassiopeia and Camelopardalis in August, is approaching 8th magnitude and may reach 6th magnitude at perihelion in September, possibly reaching naked eye visibility. It is a short term comet with an orbital period of 6.55 years.

C/2018 N1 (NEOWISE) is in southeastern Ophiuchus at magnitude 9.0 in early August and moves westward in an orbit sub-parallel to the ecliptic. By mid-month it crosses into Libra then reaches its western boundary by the 31st. Closest approach to Earth was on July 27th and perihelion is on August 2nd. As Comet Neowise and Earth separate in August, it will dim to 12th or 13th magnitude.

Mars Landers

Opportunity is halfway down the approximately 656-feet (200-meter) Perseverance Valley on the west rim of Endeavour Crater and is immersed in a cloud of dust which is part of the planet-wide dust storm which has bedeviled observers during this opposition. By June 10th the storm enveloped the rover and caused loss of communication. Since the last contact with the rover, Opportunity probably experienced a low-power fault, causing the the rover to hunker down into sleep mode which will end only when the skies eventually clear and the batteries are recharged.

Curiosity is still active because it is not subject to the same communication and functional problems as Opportunity. Instead of solar panels, it runs on the Multi-Mission Radioisotope Thermoelectric Generator, or MMRTP, an energy source that relies on the heat generated by decaying plutonium dioxide.

The recent success of mission scientists in overcoming the drilling and sample delivery problems in the drilling program allowed testing of powder collected from drilling of ancient mudstones in 2015. The powder derived was heated so as to release gases from complex organic molecules thought to be present in the powder and testing of the gases revealed the presence of numerous carbon based molecules including: Thiophene, benzene, toluene, propane, and butane. In addition, atmospheric testing during Curiosity’s residence on Mars reveals that methane abundance has varied in a periodic manner (low levels - late spring, early summer & late autumn, early winter; high levels - late summer, early autumn.) Methane on Earth is derived from biologic sources and the presence of organic molecules in the upper five centimeters of rock at the drilling sites is potential evidence for ancient biological sources. Although these results increase the possibility of ancient or current life on Mars, they are not confirmation. Both results can also result from abiotic processes.

Low frequency radar studies of the southern polar cap by Mars Express from 2012 to 2015 were analyzed by Italian scientists and interpreted to reveal a 12 mile wide area of liquid water at the base of the ice sheet. Such areas are known to exist on Earth, but Mars is too cold for liquid water unless the water is too saline to freeze.

Meteor Showers

According to Guy Ottewell’s 2018 Astronomical Calendar, August hosts the following meteor showers:

  • August 11-13 Mon: Perseids. Active Jul 17- Aug 24. ZHR ~110. 2 days after New Moon. Especially favorable.

  • August 18 SAT.: Kappa Cygnids ZHR ~3. Near 1st quarter Moon. Minor shower.

The Perseid Meteor Shower coincides with almost ideal, Moon-free skies. The meteors are fast moving and bright. They result from the debris scattered from previous passages of Comet 109/P Swift–Tuttle (the Great Comet of 1862.) The Kappa Cygnids come from a stream of debris which includes Minor Planet 2008ED69. The meteors and minor planet may result from the fragmentation of a larger body which formerly followed a orbit similar to that of the shower.

Planet Plotting

Venus (-4.1 to -4.3) is in Virgo in August and sets not long after the Sun but is bright enough to be seen in the glow of sunset. It is at maximum eastern elongation on the 17th, when it will be 45.9° from the Sun and dominate the early evening western sky, possibly exceeding -4.3 in magnitude. A thin waxing crescent Moon is about 6.0° from Venus on the 14th. Mercury is buried in the glare of sunset and sets less than an hour after the Sun. It reaches inferior conjunction on the 9th when it is too close to the Sun to be seen. At maximum western elongation of 18° on the 26th, it will be a relatively bright predawn eastern beacon. It is slightly over 5.0° of the waning crescent Moon on the 11th. Jupiter (-2.0 to -18) is in Libra in the western and southwestern evening sky. It is near the waxing crescent Moon on the 17th. In August, Saturn (+0.2 to +0.4) in Sagittarius rises in the southeast before sunset. The waxing gibbous Moon passes the ringed planet on the 21st.

Mars (-2.8 to -1.8), in Capricornus passed through opposition on the 27th and was closest to Earth (0.385 AU) on the 31st. This was its best opposition since 2003. Close oppositions include 1719 - .3740 Astronomical Units, 1766 - .3733 AU, 1845 - .3730 AU, 1924 - .3728 AU, 1956 - 0.3790 AU, 1971 - 0.3759 AU, and 2003 - 0.3727 AU 2050 - .3741 AU, 2082 - .3736 AU.

PlanetConstellation(s)MagnitudePlanet PassagesTime, Date
SunCancer/Leo-26.8New Moon10:48PM EDT, 7/12
MercuryLeo, Cancer/Leo+3.0 to +4.8 to -0.7Inferior Conjunction
Max. Western Elongation
1:00AM EDT, 8/9
5:00PM EDT, 8/26
VenusLeo-4.1 to -4.3Max Eastern Elongation1:00PM EDT, 8/17
MarsCapricornus-2.8 to -2.1  
JupiterLibra-2.0 to -1.8  
SaturnSagittarius+0.2 to +0.4  
UranusAries+5.8 to +5.7  
NeptuneAquarius+7.9 to +7.8  

During the 1956 opposition, Dick Cookman made detailed telescopic observations with his 6” diameter home made equatorial newtonian reflector and determined that Percival Lowell’s conclusion that Mars had canals was wrong. Recent observation confirmed Cookman’s determination so world governments conducted numerous Martian orbital expeditions and landings to further support his observations. In early August, Mars is still exceedingly bright at magnitude -2.8 and will diminish to -2.1 by month’s end. Telescopic views sufficient to see surface details should be spectacular if the planet-wide dust storm settles down. Best viewing will be during the first half of August with Mars big and bright, when Moonset occurs well before Mars is higher in the southeastern sky. Even through the Moon moves closer during the 1st two weeks of the month, its glare lessens as the month progresses because the Moon wanes. A waxing gibbous Moon will be above Mars in the southern sky on the 23rd, after which Mars is best seen in the early evening before Moonrise. Neptune (+7.8) and Uranus (+5.8 to +5.7) rise after Mars in Aquarius and Aries respectively in the latter evening. The waning gibbous Moon passes within 2° of Uranus on the 4th, Neptune on the 27th, and is 5° from Uranus on the 30th.

August Moon

August’s New Moon on the 12th at 5:58AM EDT is the beginning of Lunation 1183 which ends 29.26 days later with the New Moon of September on the 11th at 5:58AM EDT. A partial solar eclipse will enthrall observers in northern Canada, northern Europe and most of Asia on the 11th when the Moon comes between Earth and the Sun covering up one third of the Sun. The Full Moon on the 26th at 7:56AM EDT is known as the “Green Corn or Grain Moon.” Celts called it the “Dispute Moon,” and Colonial Americans called it the “Dog Day’s Moon.” Chinese refer to it as the “Harvest Moon,” and it was the “Corn Moon” in Medieval England. Anishinaabe (Odawa and Ojibwe people) recognize it as “Manoominike-giizis" (Ricing Moon.) Lunar Perigee (closest to Earth) is 222,500 miles or 56.14 Earth radii on the 10th at 2:07PM EDT. Apogee (maximum orbital distance) occurs on the 23rd at 7:23 AM EDT when the Moon is at 252,119 miles (63.62 Earth radii).

PlanetConstellationMagnitudeMoon PassageMoon PhaseMoon Age
SunLeo-26.85:548AM EDT, 8/12New0 days
MercuryCancer+4.35.5°N, 1:31AM EDT, 8/11Waning Crescent29.09 days
VenusVirgo-4.26°N, 10:0AM EDT, 8/14Waxing Crescent2.17 days
MarsCapricornus-2.37.0°N, 1:00PM EDT, 8/23Waxing Gibbous11.29 days
JupiterLibra-1.95.0°N, 7:00AM EDT, 8/17Waxing Crescent5.04 days
SaturnSagittarius+0.32.0°N, 6:00AM EDT, 8/25Waxing Gibbous9.00 days
UranusAries+5.82.0°S, 5:00PM EDT, 8/4Waning Gibbous21.76 days
UranusAries+5.75.0°S, 11:00PM EDT, 8/30Waning Gibbous18.71 days
NeptuneAquarius+7.82.0°S, 6:00AM EDT, 8/27Waning Gibbous15.00 days

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