Mercury Meets Venus

   Sunday evening January 11th after sunset the two inner planets Mercury and Venus will be within less than 1o from one another in a nice viewable conjunction. This conjunction is a result of both planets eastward motion away from the Sun toward their respective eastern elongations. Mercury, as the innermost and fastest of the two, will not quite catch up with Venus, and will be just a few days before it (Mercury) reaches eastern elongation. At that point Mercury reverses direction and begins moving in retrograde, westward toward the Sun and away from the still eastward moving Venus.
   See some additional information about the two planets in a previous post.

   
   
   
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Caution: Objects viewed with an optical aid are further than they appear.
   Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.

Dance of the Inner Planets

   Granted that is not an original title but it is a good description of the orbital motions of the two inner planets, Mercury and Venus, over the next couple of weeks. Both planets are on the east side of the Sun, and both are moving from superior conjunction eastward to their respective eastern elongations. Mercury, as the innermost of the two, is moving more quickly than Venus, and while Mercury will not overtake Venus, it (Mercury) will nearly do so. Follow their respective daily motions with this animated graphic, in the real world outdoors, or if your local weather has been overcast like where I live then use the slideshow below for a virtual observation!
   
    On January 11th Mercury will come within nearly 0.5o from Venus, and a few days later, on the 14th, Mercury will reach its greatest eastern elongation, while the reletively slower moving Venus reaches its eastern elongation in June. From eastern elongation Mercury will begin retrograde motion as it moves westward toward inferior conjunction on the 30th. Both are currently setting about an hour after sunset.

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[centup]
Caution: Objects viewed with an optical aid are further than they appear.
   Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.

Mercury at Western Elongation

orbital-positions   On Saturday 12 July Mercury, the innermost planet, will reach its orbital position known as greatest western elongation. At that moment Mercury, the Sun, and the Earth, would be arranged in something close to approximating a right angle as this graphic shows.
   From our perspective the orbits of Mercury and Venus appear to move from one side of the Sun to the other – out to the left (east) from the Sun to eastern elongation, then reverse and move westward (inferior conjunction) between the Earth and the Sun to western elongation. From there the inner planet moves eastward going behind the Sun (superior conjunction) and eventually reappearing on the eastern side of the Sun for an eastern elongation. Repeat over and over – do not stop!
   The banner graphic at top of page shows the orbits of both inner planets with planets where they will be on the 12th. Mercury is at western elongation while Venus is past its own western elongation and is currently moving eastward toward the Sun and superior conjunction in a few months (October).
   Mercury is currently visible as an ‘morning star’ over the eastern horizon at sunrise.

   
   
   
Caution: Objects viewed with an optical aid are further than they appear.
   Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.

Thin Moon and Planets

10 June - 9:15 pm CDT

10 June – 9:15 pm CDT

   Look westward this evening, Monday 10 June, at sunset to see the very thin waxing crescent Moon to be about 7 degrees away from the planets Mercury and Venus. Both of the planets and the Moon should almost fit within the field of view of 7×50 binoculars as this graphic shows.

Click here to go to the Qué tal in the Current Skies web site for more observing information.

Dance of the Planets

23 May to 11 June - 8:30 pm CDT

23 May to 11 June – 8:30 pm CDT

   In my posting yesterday I described the orbital motions of these three planets without the use of a graphic to help visualize that explanation. This animated graphic that is set to one-day intervals starts with today’s date and then runs for a few weeks. This gives enough time to see how both Mercury and Venus are moving eastward while it appears that Jupiter is moving in the opposite direction, west towards the Sun. Jupiter is in fact moving eastward but considerably slower than the Sun’s apparent eastward motion. The net effect is that Jupiter sets earlier and earlier as the Sun gets closer, and eventually Jupiter moves behind the Sun.

   Both Mercury and Venus were recently on the opposite side of the Sun from the Earth at superior conjunction. Coming from that relative position both planets travel eastward until they reach a point with respect to the Sun that we see as the furthest apart, or the greatest angular separation between the Sun and Mercury or Venus. This happens on either side of the Sun and are known as elongations. Since both planets are on the east side of the Sun they are both heading toward eastern elongation. In the animated graphic above you can see all of Mercury’s orbit on the east side of the Sun including the part where Mercury reaches eastern elongation and heads back toward the Sun. Because Venus is further from the sun it has a longer orbital period around the sun and likewise a longer orbital path so Venus’s orbital path on the graphic extends past the edge.

   

   Click here to go to the Qué tal in the Current Skies web site for more observing information.