December Moon at Apogee

   Our Moon reaches apogee, (greatest distance from Earth), on Wednesday December 12th. At that time the Moon will more or less be at a distance of 31.76 Earth diameters 251,765 miles (405,177 km) from the Earth.

   Does our Moon actually go around the Earth? From our perspective on the Earth the Moon appears to circle around the Earth. However, in reality, the Moon orbits the Sun together with the Earth*

   On the day of the apogee the 6-day old waxing crescent Moon, an hour after sunset local time (4:55 pm CST), will be over the southwestern horizon and joined by several planets. Over the southern horizon is the planet Mars. Neptune and Uranus are also shown however at 8th Neptune requires optical assistance or a camera to become visible, while Uranus at around 6th magnitude could be visible with binoculars or telescope.

*Click here to read my 2006 Scope on the Sky column “The Real Shape of the Moon’s Orbit”. (PDF)

Read this very informative article about the Earth-Moon system and their orbital motions, written by Joe Hanson. “Do We Orbit the Moon?”

   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to go to bobs-spaces.

Thin Waxing Moon in Conjunction with Saturn

   Saturday evening December 8th the 1.6-day young waxing crescent Moon will be in conjunction with the outer ringed planet Saturn. The two will be within about 3o from each other. Joining the Moon and Saturn is the Dwarf Planet Pluto, and further to the east are the planets Uranus, Neptune, and Mars.

   Within the field of view of 7×50 binoculars, in addition to the Moon and Saturn, are several Messier Objects, M-22, M-25, and M-26. These may be a challenge to see given that they are low over the western horizon and by the time the sky is darker they will have set or are just about to set.

   
   
   
   
   
   
   
   
   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to return to bobs-spaces.


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Thin Moon Conjunction with Mercury

   Wednesday morning December 5th the very thin 28-day old waning crescent Moon will be within 4-5o from the innermost planet Mercury. Venus shines very brightly above or west from the Moon. About an hour after the Moon and Mercury have risen the outer planet Jupiter will rise above the eastern horizon.

   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to return to bobs-spaces.


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Moon Conjunction with Spica and Venus

   Monday morning December 3rd the 28-day old thin waning crescent Moon will be within 5o from the blue white star Spica in Virgo the Harvest Maiden, and about 2o from the inner planet Venus.

   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to return to bobs-spaces.


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Mars Reaches Eastern Quadrature

orbital-positions   Monday December 3rd the position of the planet Mars, with respect to the Earth and the Sun, places this planet at what is called eastern quadrature. At that orbital position Mars, and actually any outer planet, is at a 90 degree angle from the Earth as this graphic shows, and the banner graphic at the top of the page shows. Think first quarter Moon as that is a fair comparison of the relative positions of Earth, Sun, and Mars.

   At this position Mars follows the Sun across the sky from east to west as the Earth is rotating, meaning that Mars rises after the Sun and then sets after the Sun. Mars, with an apparent magnitude of 0.0, is about 2o from 8th magnitude Neptune.

   
   
   

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Moon in Conjunction with Regulus

   Thursday morning November 29th the 22-day old waning gibbous Moon will be 1-2o from the heart of Leo the Lion, the star Regulus. By sunrise the Moon and Regulus will be over the southern horizon. At about that time Venus, shining very brightly, is still close to Spica as the two rise a couple of hours before the Sun rises.
   This is also the time of the year when the winter circle of constellations (Taurus, Auriga, Gemini Twins, Canis Minor, Canis Major, and Orion) start showing up over the horizon during the late evening hours.

   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to return to bobs-spaces.


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Mercury at Inferior Conjunction

orbital-positions   Tuesday November 27th the innermost planet Mercury reaches inferior conjunction. At inferior conjunction Mercury will move between the Earth and the Sun – much like the position of the Moon at new phase. The graphic to the right shows the planet positions relative to the Earth and Sun for both inner planets and outer planets.

   At this inferior conjunction Mercury will not be directly in line with the Earth and the Sun – on the ecliptic. Mercury has an orbital inclination of 7o with respect to the ecliptic. So like our Moon, Mercury during each complete orbit, will cross the plane of the ecliptic moving north (ascending node) and also moving south (descending node). For this inferior conjunction Mercury will be about 5o north from the ecliptic, approaching its maximum angle of 7o.

   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to return to bobs-spaces.


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