Moon – Mars Conjunction

   Saturday evening January 12th, after sunset, the 7-day old waxing crescent Moon will be about 4o from the planet Mars. The two will easily fit within the field of view of binoculars.

   
   
   

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January Moon at Apogee

   Our Moon reaches apogee, (greatest distance from Earth), on Wednesday January 9th. At that time the Moon will more or less be at a distance of 31.83 Earth diameters 406,116 km (252,349 mi.) 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 4-day old waxing crescent Moon will be over the southwestern horizon at sunset local time.

*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 return to bobs-spaces.


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January Moon at Descending Node


   Monday December 7th the 2-day old waxing crescent Moon will be crossing the plane of the ecliptic moving south. This is known as the descending node, one of two intersections the Moon’s orbital path (dark green line) has with the ecliptic.
   
   
   

   On the day of the node crossing the 2-day old thin waxing crescent Moon will be over the southwest horizon about an hour after the Sun sets.

   
   
   
   
   

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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Venus Reaches Western Elongation

inner-planets-positions   Sunday January 6th Venus reaches the point in its orbit called greatest western elongation. As this graphic shows the inner planet Venus, or Mercury, is more or less at a right angle (90o) from the Sun and Earth at western elongation. From the surface of the Earth, your backyard, for example, Venus is to the right, or western side of the Sun and is rising before the Sun.

   On the day of the elongation Venus will be very visible over the southeastern horizon at or before sunrise local time. Venus is joined by the planet Jupiter, about 13o below Venus, east from Venus. The reddish star Antares in Scorpius the Scorpion is also about 13o from Venus, and is about 6o from Jupiter. If the skies are dark enough the Milky Way should be visible rising toward the southwest.

   At western elongation Venus, or for that matter Mercury the other inner planet, is as far out from the Sun as we see them and as a result Venus or Mercury will rise at the latest time in this orbit. On the day of the western elongation Venus will be 46.9o from the Sun. From western elongation forward Venus or Mercury will be moving eastward toward the Sun and each day rising closer and closer to the time of sunrise. As the planet moves eastward it is moving further away from the Earth toward superior conjunction on the opposite side of the Sun.


    As the distance between the Earth and Venus, or Mercury, increases combined with the decreasing angle between the planet, the Earth, and the Sun, Venus or Mercury decreases in apparent size and also waxes through gibbous phase shapes but we never see it at a full phase since that is at superior conjunction.

   
   
   

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 Crescent Moon Conjunction with Jupiter

   Thursday morning January 3rd the 27.25-day old thin waning crescent Moon will be within 3-4o from the outer planet Jupiter. The two will easily within the field of view of binoculars. Jupiter is about 5-6o from the heart of Scorpius the Scorpion, the reddish star Antares.

   
   
   

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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Saturn at 2018 Solar Conjunction

10dec-saturn-solar-conjunction   Wednesday January 2nd the planet Saturn will have reached the astronomical coordinates that officially place it at solar conjunction. From our perspective the planet is behind the Sun, or on the opposite side of the Sun from the Earth.
   In reality it is not as much as Saturn moving behind the Sun as it is the Sun passing in front of Saturn – or so it seems. As a distant outer planet Saturn moves more slowly around the Sun than the Earth does. One year on Saturn is equal to 29.7 years (10,832 days) on Earth. So in one day Saturn would travel how much of the 360o orbit around the Sun? That would amount to approximately 0.033o each day.
   The Sun, in its apparent motion along the ecliptic moves at the rate the Earth is moving which is 0.99o each day. So with the Sun’s apparent motion (0.99o/day) it quickly, relative to Saturn, passes Saturn while both are moving eastward. So with that in mind you could start watching for Saturn to reappear in the morning skies later next month.

   
   
   

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 Venus and Ceres

   Tuesday morning January 1st the thin 25-day old waning crescent Moon (apparent magnitude -10.96) will be within 3-4o from the inner planet Venus (apparent magnitude -4.47) and 1-2o from the Dwarf Planet Ceres (apparent magnitude 8.0). All three will fit within the field of view of 7×50 binoculars.

   
   
   

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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