Highlights: Comet Journal, Martian Landers, Planet Plotting, Meteors, October Moon
Focus Constellations: Camelopardalis, Perseus, Andromeda, Cassiopeia, Cepheus, Cygnus, Lyra, Hercules, Draco, Ursa Major, Ursa Minor
Comet Journal
Comet C/2006 W3 (Christensen) has briefly brightened once again to 8th magnitude as it descends through Aquila in the southwestern evening sky. It will continue southward along the edge of the Milky Way and exit Aquila in November when it disappears into evening twilight.
C/2007 Q3 (Siding Spring) is at 9th magnitude and reaches perihelion on October 7th. It is in southernmost Leo in October and has descended into the sunset. It rises in the eastern sky before dawn where it is better positioned for viewing for the rest of 2009 as it moves into Coma Berenices.
Comet 88P/Howell (2009) has joined Comets Christensen and Siding Spring as one of the comets brighter than magnitude 10 in the autumn sky. It is difficult to find since it's low in the western sky in Scorpius at sunset.
Martian Landers
In August and early September Opportunity circumnavigated Block Island, a 28 inch diameter boulder in the middle of Meridiani Planum in order to complete a thorough analysis of the unusual bluish colored rock. The rover had sidetracked over 200 meters from its course toward Endeavour Crater in order to make its approach.
Alpha particle X-ray spectrometric analyses reveal that Block Island has a chemistry consistent with nickel-iron meteorites. It also exhibits the Widmanstatten pattern typical of such meteorites. Similar meteorites found on Earth are radiometrically age dated at more than 4.5 billion years and the pattern is thought to have formed by shrinkage as the metal cooled. According to NASA, "one iron-nickel mineral, kamacite, formed thin layers along the surface of crystals of another, taenite, which contains less nickel. The two minerals differ in their resistance to either etching by acid or erosion by wind-blown sand, so those processes can make the pattern visible."
The meteorite displays the bluish metallic appearance on one side similar to Heat Shield Rock, another meteorite discovered by Opportunity. The other side has a much rougher texture with numerous protrusions possibly caused by chemical weathering. Further testing may reveal the degree of physical and chemical weathering to which the meteorite has been subjected indicating how long ago it fell.
Since the meteorite is too large to have survived a fall through the low density atmosphere of present day Mars, a recent descent would indicate that atmospheric density may vary on a short time scale. Discovery of frozen water and oxidized minerals in the rocks and soils of Mars attest to an ancient thick atmosphere which would account for the weathering if the descent was billions of years ago, but a recent fall would support the theory of wild deviations in atmospheric density due to the observed large variation of tilt of the Martian axis. Such deviations might produce periodic climate changes allowing for occasional blooming of life similar to Earth's pulse of life as it retreated to and expanded from the low latitudes in synchrony with advance and retreat of glaciers over the last two million years.
On Sol 2004 (Sept. 12, 2009), Opportunity departed Block Island and headed westward with a 70 meter (230-foot) drive. The plan is to bypass a region of large dunes before turning south and east toward Endeavour. After 2 additional 70 meter westward drives on Sols 2006 and 2007, and four more of 55, 71, 71, and 59 meters on the following sols, Opportunity’s total odometry on Mars as of Sol 2014 (Sept. 23, 2009) is 17,717.20 meters (over 11 miles).
The scientific team in charge of designing a methodology for the extraction of the Spirit rover from the soft sediment of Troy on the west side of Home Plate is continuing its investigation. In the meantime, Spirit is proceeding with remote observation of surrounding soils, rocks, landforms and atmosphere. Testing on Mars and communication with Earth were interrupted by a major dust storm that started on Sol 1995 and reduced available solar power to 744 watts hours on Sol 2001 (Aug. 19, 2009) and to 322 watt-hours on Sol 2007 (Aug. 25, 2009). Solar energy production increased to 564 watt-hours on Sol 2014 (Sept. 2, 2009) as the storm decreased, but residual atmospheric dust continued to reduce production to the low 400's during most of September. A high-gain antenna anomaly on Sept. 15th which is expected to be fixed by the end of the month has also delayed communication.
Planet Plotting
The predawn skies of October promise numerous conjunctions and near conjunctions of the planets Mercury, Venus and Saturn. Mercury reaches greatest western elongation at 10PM on the 5th when it provides the best morning apparition of 2009 at magnitude 0.6. On the 1st, it rises in Virgo 45 minutes after brilliant Venus (-3.9) and a little over an hour before sunrise. Closest approach of the two occurs before they rise on October 8th. Saturn (1.0) has emerged from its conjunction with the Sun on September 17th and rises about 20 minutes after Mercury early in the month. The two are less than one third of a degree apart on the 8th, one of the closest conjunctions of 2009. On the 13th Venus and Saturn are about 0.5 apart.
Jupiter (-2.6) dominates the evening sky in Capricornus and Neptune (7.8) is about 5° farther west. Uranus (5.7) is south of the circlet in eastern Pisces. All are evening planets which are visible in the SSE in the early evening.
Planet.......Constellation......Magnitude .........Planet Passages
Sun...........Virgo.................-26.8
Mercury......Virgo................-0.3 to -1.2........Venus, 5.8°WNW, .....................................................................2AM EDT, 10/8
.............................................................Saturn, 0.32°NE,
.....................................................................1AM EDT, 10/8
Venus........Leo/Virgo..........-3.9..................Mercury, 5.8°ESE,
.....................................................................2AM EDT, 10/8
.............................................................Saturn, 0.52°NNE,
....................................................................6AM EDT, 10/13
Mars..........Gemini/Cancer..+0.8 to 0.5
Jupiter.......Capricornus.......-2.7 to -2.5
Saturn.......Virgo................+1.1 to 1.0........Mercury, 0.32°SW,
....................................................................1AM EDT, 10/8
..............................................................Venus, 0.52°SSW,
....................................................................6AM EDT, 10/13
Uranus.......Pisces...............+5.7
Neptune.....Capricornus......+7.8
Meteors
The Draconid Meteor shower on the 8th and 9th is likely to be quite minor and will be difficult to view in the light of the waning gibbous Moon. The Orionid Meteor Shower occurs throughout October and could generate 25-30 meteors per hour in dark skies before dawn on the 21st, long after the setting of waxing crescent moon. The Orionids are high speed meteors resulting from Earth plunging through the debris field remaining from recent passages of Comet Halley which last lit up the skies in 1986.
October Moon
The Full Moon of October on the 4th at 2:10AM EDT is the “Harvest Moon”. Prior to the 1700's, the meaning of "harvest" had evolved into a term utilized to refer to the autumn season when crops were gathered and reaped. All full moons rise at sunset then rise later on succeeding nights. Rising time normally advances about 50 minutes per day, but this delay is less in Autumn for the northern midlatitude regions, decreasing to about 30 minutes in early autumn. The days following the full moons of the autumn months of September and October share the characteristic of rising soon after sunset and provide light for continued harvesting into the evening.
In colonial America the September Full Moon was called the "Harvest Moon" and October's Full Moon was the "Hunters Moon". Current definitions for the "harvest moon" are that it is the full moon closest to the equinox. It's followed by the "Hunters Moon". In medieval England the October Full Moon was called the "Blood Moon" and the Chinese call it the "Kindly Moon". The Celts thought of it as the "Harvest Moon". For the Anishnaabe (Chippewa and Ojibwe) it is "Binaakwe-giizis" (Falling Leaves Moon). The length of this lunation is 29.45 days.
Planet..Constellation..Magnitude..Moon Passage........Moon Phase/Age
Sun..........Virgo........-26.8.....1:33AM EDT 10/18..............New
............................................................................~ 0 days
Mercury...Virgo........-1.0........6.8°SSW, 1AM EDT 10/17....Waning ...............................................................................Crescent ..........................................................................~ 28.43 days
Venus......Leo/Virgo..-3.9.......6.1°SSW, 10AM EDT 10/16..Waning ...............................................................................Crescent ..........................................................................~ 27.8 days
Mars..Gemini/Cancer..+0.6 .....1.1°SSW, 9PM EDT, 10/11...Waning ...............................................................................Crescent ..........................................................................~ 22.8 days
Jupiter....Capricornus..-2.5......3.0°N, 5AM EDT, 10/27......Waxing ...............................................................................Gibbous ..........................................................................~ 9.14 days
Saturn.....Virgo............+1.1.....6.4°SSW, 3AM EDT, 10/16...Waning ...............................................................................Crescent ..........................................................................~27.51 days
Uranus......Pisces.........+5.7.....6°NW, 10PM EDT, 10/2........Waxing ...............................................................................Gibbous ..........................................................................~13.8 days
..........................................6.0°NNW, 5AM EDT, 10/30...Waxing ...............................................................................Gibbous ..........................................................................~ 12.1 days
Neptune..Capricornus..+7.8.....2.9°NNW, 3PM EDT, 10/27....Waxing ...............................................................................Gibbous ..........................................................................~ 9.56 days |
