December 2015 – Skies News

Focus Constellations: Camelopardalis, Ursa Major, Ursa Minor, Draco, Cepheus, Cassiopeia, Pegasus, Andromeda, Pisces, Perseus, Auriga, Taurus, Gemini

Comet Journal

20km. wide C/2013 US10 (Catalina) was in southern hemisphere skies when it reached perihelion (closest to the Sun) on Nov. 15th slightly inside Earth’s May position in orbit. Catalina moved northward through the ecliptic on Nov. 26 and into eastern Virgo. It will continue northward, rising at 6th magnitude between Virgo and Bootes about 1:30AM EST on Christmas Eve and approaching Arcturus in Bootes at the end of December. It will remain in northern skies during the winter when it may reach naked eye visibility at 5th magnitude. The comet will be closest to Earth on January 17th and within 8° of Polaris on Jan. 31st. It is a long period first time comet from the Oort Belt, but gravitational influences during the passage through the inner solar system is accelerating it to solar escape velocity, never to return.

The array of two 1.8 m Ritchey-Chretien telescopes known as PanSTARRS which is located at Haleakala in Hawaii was commissioned by the US Air Force with a primary mission to detect near-Earth objects that threaten to impact Earth. It is expected to create a database of all objects visible from Hawaii (three-quarters of the entire sky) down to apparent magnitude 24. In 2014, Comet C/2014 S2 (PanSTARRS) was discovered with the array and is now at 9th magnitude and located in Draco. It is expected to pass through perihelion on Dec. 9th and will complete its circuit through Draco and head toward the cup of the Big Dipper during the winter.

A year ago, Comet C/2013 X1 (PanSTARRS) was discovered by the array and is now at 9th magnitude in Andromeda. It will reach Pegasus by Christmas then move into Pisces during the winter. The comet will be at perihelion on April 20, 2016 between Pisces and Aquarius and it will be closest to Earth in June when it may reach magnitude 7.5.

Mars Landers

Opportunity is in Marathon Valley to examine the phyllosilicate clay minerals which were discovered via satellite spectral studies. The rover has been stationary since Sol 4166 (Oct. 13, 2015) as it is now positioned at its winter haven on a north facing slope on the south side of the valley. From the 13th until early November, the rover’s activities were constrained by the winter power levels but despite limited power, it conducted a campaign of Panoramic (Pancam) Camera color imaging of Marathon Valley. Opportunity also is engaged in an in-situ (contact) science campaign at the current location. On Sols 4175, 4177 and 4180, Opportunity collected a 2×2 Microscopic Imager (MI) mosaic followed by the placement of the Alpha Particle X-ray Spectrometer (APXS) on a different surface target.

On Sol 4186 (Nov. 2, 2015), commands were sent to the rover to enable the use of Flash memory and to spend the week returning science data already in Flash memory. Although those commands were successful, the rover experienced an amnesia event on Sol 4186 (Nov. 2, 2015). On Sol 4187 (Nov. 3, 2015), the rover successfully mounted Flash and began the return of the science data. Opportunity has now traversed 26.48 miles (42.62 kilometers) over the Martian surface. Solar energy in the last month ranged from 332 to 344 watt hours per day.

Curiosity is climbing the lower slopes of Mt. Sharp over the sandstones of the Stimson Unit. The dark sandstone of the Stimson over which the rover has been traveling since August 27th displays some large scale cross-bedded layers typical of windblown sand deposited as dunes on Earth. In September, Curiosity followed a southward course parallel to the cross- bedded layers in order to reach an access location for drilling. The rock drilled at “Big Sky” turned out to be the very clean sandstone which mission scientists wanted to sample. They also drilled an adjacent outcrop (Greenhorn) which looked as though it had been altered by ground water containing abundant dissolved chemicals.

The next target for the rover is a large active dark colored dune in a nearby dune field. The rover has examined many sand ripples during its journey but has not observed an active dune. “Dune 1,” which is as large as a football field and as tall as a two story building is actively moving downwind as sand is blown up the upwind side and slides down the southerly lee side. The dark color of the dunes is probably due to sand size grains of the mineral olivine, an iron-magnesium silicate found within dense igneous rocks such as volcanic basalt. The variety of dark and lighter colored areas may be due to density and/or size sorting by the wind or may result from differential alteration by water. Dunes on Earth exhibit different textures and much smaller surface ripples than those in the adjacent dunefield, possibly due to the lower air pressure on Mars or due to alternative causes which may be discovered during the pending observations.

Scientists from NASA’s JPL and the California Institute of Technology recently determined mechanisms accounting for the low density of the Martian atmosphere. From data gathered in the past few years about evidence for an early warm Mars with abundant water, the atmosphere must have been much denser with sufficient levels of carbon dioxide to produce an adequate Greenhouse Effect. Levels of carbon currently stored in the Martian rocks can’t account for the amount lost which must be due to carbon dioxide lost to space over the last 3.8 billion years due to bombardment by solar wind and solar ultraviolet radiation.

Meteor Showers

The Geminid Meteor Shower will light up mid-December night skies three days after New Moon. It will plateau at 50 to 130 meteors per hour in dark skies between the morning and evening of the 14th. The meteors will appear to emanate from a radiant in Gemini which will be overhead at 2AM EST on the 14th. The shower is caused by debris from former passages of the object 3200 Phaethon, an Apollo Asteroid that crosses the orbits of Mercury, Venus, Earth, and Mars as it circuits around the Sun.

The Ursid Meteor Shower peaks on the 23rd, two days before the Christmas Full Moon. The remnants of Comet 8P Tuttle which last passed Earth in 2008 and will return 2021 typically display about ten meteors per hour and occasionally produce up to 50 per hour when the comet is near. The glare of the gibbous Moon will overwhelm the shower this year.

The Phoenicid, Puppid, and Monocerotid showers on the 6th, 7th, and 9th are minor southern hemisphere showers.

Winter Solstice

The December Solstice on the 21st occurs at 11:48PM EST when Earth is at the position in its orbit where the polar axis is at maximum tilt away from the Sun causing perpendicular rays from the Sun to fall on latitude 23.5° S. At 45° N latitude, the noon Sun appears 21.5° above the south point on the horizon, its southernmost position of the year. The low angle forces sunlight to pass through much more atmosphere to reach the surface, greatly reducing its intensity. The coldest part of the northern hemisphere winter usually occurs during succeeding months due to the tendency for the Earth’s surface to retain heat from the previous season. This year, that tendency is exaggerated by the El Nino effect whereby excessive quantities of heat have been stored in tropical Pacific water, delaying the onset of winter and possibly moderating its effects.

Planet Plotting

Saturn (+0.5 to +0.4) in Ophiuchus is a predawn planet in the last half of December, rising in the southeast just before the Sun. Morning planets also include Venus (-4.2 to -4.1) and Mars (+1.5 to +1.3) in Virgo, and Jupiter (-2.0 to -2.2) in Leo. which line up quite nicely above the southeastern horizon in early December.

Neptune (+7.9) in Aquarius and Uranus (+5.8) in Pisces are evening planets setting around midnight. Mercury in Ophiuchus sets slightly after the Sun in early December and appears higher in the sky each evening as the month progresses. It will be farthest away from the Sun on the 28th when it reaches its Greatest Eastern Elongation of 20°.

Planet……Constellation……Magnitude……Planet Passages

Sun..Ophiuchus, Sagittarius……..-26.8…………..New Moon, ………………………………………………………12/11, 5:29AM EST Mercury..Ophiuchus, Sagittarius..-0.8 to -0.6
…………………………………………………….Max. East Elongation ……………………………………………………..12/28, 10:00PM EST Venus….Virgo, Libra…-4.2 to -4.1
Mars……Virgo………….+1.5 to +1.3
Jupiter……Leo…………..-2.0 to -2.2
Saturn…Ophiuchus….+0.4 to +0.5 Uranus…….Pisces………………+5.8
Neptune…Aquarius……………+7.9

December Moon

Lunation 1150 begins with the New Moon of December 11th at 5:29AM EST. It ends 29.13 days later with the New Moon on January 9th at 8:31PM EST.

The Full Moon for December in Taurus is at 6:11AM EST on the 25th. It is called the “Moon before Yule” or “Long Night Moon”. Colonial Americans named it the “Christmas Moon” and it was the “Oak Moon” to the Medieval English. It is the 13th Moon of 2015 due to two Full Moons in July and is designated by the Anishinaabe (Odawa and Ojibwe) of the northern Great Lakes as “Gitchi-manidoo-giizis” (Great Spirits Moon). Celts called it the “Cold Moon” while for the Chinese it is the “Bitter Moon.”

Apogee distance (maximum orbital distance) is 251,531 miles (63.46 Earth radii) from Earth on the 5th at 9:56AM EST. Perigee distance is 228,924 miles or 57.76 Earth radii on the 21st at 4:00AM EST.

Planet..Constellation..Magnitude..Moon Passage..Moon ………………………………………………………………….Phase/Age

Sun….Ophiuchus….-26.8…………………..5:29AM EST, 12/11 ………………………………………………………………New ~ 0 days Mercury..Sagittarius..-0.6…………..7.2°N, 9AM EST, 12/12 …………………………………………Waxing Crescent ~ 1.15 days Venus……Virgo……..-4.2…………0.7°N, Noon EST, 12/7 …………………………………………Waning Crescent ~ 25.97 days Mars……..Virgo…….+1.5…………0.1°S, 10PM EST, 12/5 …………………………………………Waning Crescent ~ 24.38 days Jupiter……Leo.. …….-2.0…………1.8°S, 1AM EST, 12/4 …………………………………………Waning Crescent ~ 22.51 days
…………………………..-2.2…………1.5°S, 1PM EST, 12/31
…………………………………………Waning Gibbous ~ 19.81 days
Saturn..Ophiuchus..+0.4………….3.1°N, 10AM EST, 12/10 …………………………………………Waning Crescent ~ 28.88 days Uranus….Pisces…….+5.8………….1.2°S, 8PM EST, 12/19 …………………………………………Waxing Gibbous ~ 8.60 days
Neptune..Aquarius…+7.9…………3.0°N, 3AM EST, 12/17 …………………………………………Waxing Crescent ~ 5.90 days