Venus and Jupiter in Motion

   If the morning skies are clear and the temperature is tolerable go out before sunrise local time and look toward the east. The two brightest stellar objects are the planets Venus (brightest) and Jupiter. A few degrees from Jupiter is the reddish star Antares in Scorpius the Scorpion. Dwarf Planet Ceres is also in this part of the sky but it is too dim to be seen with the unaided eye. As the graphic shows this is also near the Milky Way but seeing that would require much darker skies than many of us live under.

   Both planets are in motion as they orbit the Sun following their respective orbital path. As an inner planet and much closer to the Sun Venus moves more quickly than Jupiter so as days pass Venus will noticeable move more so than Jupiter. Venus was at its western elongation last month and now Venus is in the part of its orbit where it is moving eastward toward the Sun. As Venus moves in that direction Venus will catch up to and then pass Jupiter, coming the closest on January 23rd.
   The animated graphic is set for 1-day intervals from January 15th to January 31st.
   For comparison Venus moves 1.6o each day while Jupiter moves 0.083o each day. The Earth is also in motion and moves about 1.0o each day. So as the Earth moves the sky appears to move toward the west and as this happens Saturn comes into view toward the end of January. The waning crescent Moon shows up also at the end of the month.

   
   
   

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Moon and the Hyades

   Wednesday and Thursday January 16th and the 17th the waning gibbous Moon will be passing past the open star cluster the Hyades and the reddish star Aldebaran. This is a v-shaped group of stars that make up the face of Taurus the Bull. The Hyades is one of two open star clusters in the constellation Taurus. The other is a small dipper-shaped group of stars, the Pleiades, located on the shoulder of Taurus.

   
   
   

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 – Uranus Conjunction

   Monday evening January 14th the 9-day old waxing gibbous Moon will be about 6-7o from the outer planet Uranus. Both are close enough to fit within a binocular field of view.
   However don’t realistically expect to see Uranus as Uranus has an apparent magnitude of 5.78 compared to the much brighter -12.0 apparent magnitude of 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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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.

   
   
   
   
   

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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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