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January Skies 2007


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January Skies 2007- by Dick Cookman

Highlights: Comet Journal, Martian Landers, Planet Plotting, Meteors, January Moon
Focus Constellations: Cepheus, Cassiopeia, Perseus, Auriga, Taurus, Gemini, Lynx, Ursa Major


Comet Journal


Comet C/2006 P1 McNaught was discovered by Robert McNaught in August, 2006 and may reach 2nd or 3rd magnitude in January. It is approaching Earth from the far side of the Sun and passed above the Sun in late December. It will be closest to the Sun (perihelion) on January 2nd when it is between the Sun and Mercury 5 days before Mercury's superior conjunction with the Sun on January 7th. Under clear skies on New Years Eve, fortunate observers in the northern US may catch a glimpse of the comet in Scutum on the west-northwest horizon at dusk. It will then disappear into sunset and will reemerge in late January at about 6th magnitude. Southern observers may look for it in Sagittarius, south of the rising Sun.

10th magnitude Comet 4P/Faye is in Cetus during most of January and enters Taurus at month's end. It passes north of Mira on the 10th. It's perihelion was in November, 2006 just beyond the orbit of Mars. Best viewing will be in mid to late January when the waning Moon rises later in the evening.

Comet 29P/Schwassmann-Wachmann 1 is north of the Pleiades in Taurus following its opposition in mid-November, 2006. Even though the comet is beyond the orbit of Jupiter, it is still at magnitude 11-12. As Earth orbits away from it, the comet will diminish in brightness in 2007.

Martian Landers

Spirit and Opportunity have been provided with new software for their onboard computers based on software developed for NASA’s Space Technology 6 “thinking spacecraft.” Rover computers can now recognize certain types of features and select only the relevant parts of those images. The new software looks for changes from two consecutive images of the same field of view. It also looks for nonuniform features in the portion of an image it recognizes. Another feature, called “visual target tracking,” enables a rover to keep recognizing a designated feature as the rover moves.

Visual target tracking can be combined with a third new feature -- ability to calculate where it is safe to reach out with the contact tools on the rover’s robotic arm without input from the crew on Earth. The new software enables enhanced mapping of the surroundings and allows rovers to better navigate complex terrain by thinking several steps ahead.

Opportunity is on the edge of Victoria Crater, almost 2/3 as big as Meteor Crater in Arizona and dwarfing Endurance Crater where the initial landing occurred on January 25, 2004. If Opportunity can successfully descend into the crater, it may discover much about the ancient history of Mars since the crater is much deeper and exposes much older rocks than those found in Endurance Crater. From Sol 994 (November 10th) until Sol 1002 the rover moved from Cape Verde to Cape St. Mary as part of a clockwise sojourn around the crater in search for a descent route. After a week of observations, Sols 1009 to 1016 were devoted to continuing to an alcove in the crater wall called Bottomless Bay where further observations proceeded until Sol 1026. The rover then embarked around the bay, observing with its cameras and spectrometers through Dec. 24th (Sol 1037). Total travel on Mars by Dec. 21st has been 9,758 meters (6.1 miles).

After circuiting the northern margin of Home Plate plateau (diameter - 90 meters) last February and March, Spirit proceeded toward McCool HIll on the plateau's southeastern edge. As it skirted the north side of the hill, one of its wheels failed as a result of stalling of the right front actuator. It continued another 20 meters over the next 9 sols while NASA scientists attempted to analyze the wheel problem, then it returned to the southern slope of McCool Hill to establish a winter home at Low Ridge Haven. From Sol 805 until Sol 1009, Spirit endured Mars' winter months and conducted limited study of its surroundings. Since the conclusion of its winter hibernation, Spirit has examined dozens of rock and soil targets and conducted numerous atmospheric observations as it meandered over McCool Hill's southern slope from Sol 1010 (Nov. 5th) until Sol 1057 (Dec. 22nd), limping along on 5 wheels and observing new targets. One of the rocks it examined (King George Island) is made up of exceptionally rounded fragments which show evidence of deposition in an active water or wind environment. The rover also completed a 14 sol excursion to approach a new rock target referred to as Esperanza (hope) which is composed of unusual clasts or fragments. Since its arrival on Mars almost 3 years ago, the rover has traversed a total of 6,886.80 meters (4.28 miles).

Planet Plotting


Mercury (-1.1) in Capricornus will ascend in the west after sunset during the last two weeks of January. It will be below a dominating Venus (-3.9) which moves from Capricornus into Aquarius. Both evening stars will continue to dominate the western early evening skies through January and most of February after which Mercury descends back into the sunset. Look for dim Uranus (5.9) above brilliant Venus early in the month.

On the 18th, although Venus will be within 1.4° of Neptune at 1 PM EST, nearby Neptune will still be difficult to observe in the sunset. Both Neptune (8.0) and Uranus will be lost in the twilight when Mercury makes its appearance late in January.

Mars (1.5) moves from Ophiuchus into Sagittarius and fades into the dawn glow in January making observation difficult. Observers will have to wait until summer for Mars to brighten as it begins its march toward December opposition when it will outshine Sirius and dominate the sky before moonrise on Christmas Eve.

Saturn (0.1) in Leo will continue to brighten as it approaches opposition in February. It rises in the early evening and is the brightest planet in the sky after Mercury and Venus set and before the early morning rise of Jupiter (-1.8). The glistening rings of Saturn, which are easily visible at medium power in a small telescope have worthy morning rivals in the belts and zones and moons of Jupiter in Scorpius, close to brilliant red supergiant Antares.

Meteors

The Quadrantid Meteor Shower emanates from a former constellation between Draco and Bootes. It peaks on the night of 3rd/4th and is best observed before dawn on the 4th. Don't expect to see the 100+ meteors per hour occasionally observed in very dark skies with no light pollution since the shower's peak occurs less than 24 hours after Full Moon.

January Moon


January's Full Moon is the "Moon after Yule" or the "Old Moon". It is slightly northeast of the "Praesepe" (M-44) in Cancer and occurs at 8:57 AM EST on Jan. 3rd. Colonial Americans called the first Moon of the New Year the "Winter Moon", and the Celts referred to it as the "Quiet Moon". It is the "Holiday Moon" in China and was the "Wolf Moon" in medieval England. The Anishnaabe (Chippewa and Ojibwe) designate it as the "Gichi-manidoo-giizis" (Great Spirit Moon).

If we could see it during both objects during the day, we would see the waning gibbous Moon pass within 0.9° of Saturn at 1 PM EST on January 6th. That evening, Saturn will be highlighted by the nearby Moon. Then, on the morning of the 15th, the waning crescent Moon is near Jupiter prior to its passage within 6° of the planet at noon. On the following morning, a smaller waning crescent Moon passes 5° to the south of Mars at 9 PM EST and a 2.4 day old waxing crescent Moon is near Venus and Neptune on the evening of the 20th after it passes Neptune at 8 AM EST and within 0.8° of the Venus at noon EST.

The Full Moon of January occurs 7 hours before Earth is closest to the Sun. The Earth's orbit ranges from within 91.5 million (perihelion) to 94.5 million miles (aphelion) from the Sun. The resulting 3 million mile variance is slightly more than 3%, but the resulting temperature difference on Earth is overwhelmed by the effects of the tilt of the Earth and the distribution of land and water on Earth. The temperature moderation due to larger ocean area in the southern hemisphere and the temperature exaggeration due to larger continental area in the northern hemisphere vastly outweigh the effects of solar distance. Even though northern hemisphere winters occur at perihelion and those of the southern hemisphere occur at aphelion, our winters are colder due to the relative absence of oceans. Similarly northern hemisphere summers are hotter even though Earth is at aphelion during our summers.

Perihelion has not always occurred in January. The orbit of the Earth is gradually revolving like an elliptical hula hoop and requires about 100,000 years for one circuit. Similarly, the direction and amount of tilt of the Earth's axis varies through time as the axis requires 26,000 years to complete one wobble. Since these motions are in opposite directions, combining them produces a cycle of about 21,000 years in which winter at perihelion and summer at aphelion reoccur in the northern hemisphere. The resulting mild summers which limit melting favor development of glaciers like those formed 21,000 years ago when the most recent pulse of glaciation started. Hot northern summers when Earth was at perihelion 10,500 years ago may have instigated their demise.




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