Venus at Eastern Elongation

inner-planets-positions   Thursday August 16th Venus reaches the point in its orbit called greatest eastern elongation. As this graphic shows an inner planet, Venus or Mercury, is more or less at a right angle (90o) from the Sun and Earth at eastern elongation. From the surface of the Earth, your backyard, for example, Venus is to the left, or eastern side of the Sun and is setting after the Sun.

   At eastern elongation the angle between Venus and the Sun is at its greatest, which for this elongation Venus will be 45.9o from the Sun. In terms of viewing Venus, this is as about as late as Venus will set, about 4 hours after sunset local time, meaning for some Venus may set close to midnight local time. This animated graphic shows Venus at sunset, then with Venus’s orbit shown, and then with the horizon removed to see where the Sun is relative to Venus.

venus at eastern elongation   From eastern elongation forward Venus will be moving westward toward the Sun, and each day setting closer and closer to the time of sunset. By October Venus will have orbited to inferior conjunction – between the Earth and the Sun. During this part of the inner planet orbit, from eastern elongation to inferior conjunction, the distance from Earth decreases and the apparent size of Venus increases. Venus also goes through phase changes much like our Moon, and so from eastern elongation to inferior conjunction Venus wanes from a small appearing gibbous phase to an increasingly thinner crescent phase.
   
   
   
   

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Mercury at Eastern Elongation

orbital-positions    On Thursday July 12th Mercury, the innermost planet, will reach its orbital position known as greatest eastern 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 – from superior conjunction, behind the Sun, out to the left (east) from the Sun to eastern elongation, then reverse and move westward through (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!

   Currently Mercury is visible over the western horizon at sunset local time. Joining Mercury are the planets Venus, Jupiter, and Saturn. Mars rises about an hour after Mercury 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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Like Ships Passing in the Night

   Over the next week or so the two inner planets will pass by each other coming the closest on the 19th when the two will be less then 4o from each other. With only casual observation one should notice that both planets are moving with respect to each other, but in opposite directions. Mercury is recently past its eastern elongation and is now moving westward, in retrograde, toward the Sun and inferior conjunction. On the other hand, or orbit, Venus is moving eastward out from a recent superior conjunction, opposite side of the Sun, toward its own respective eastern elongation.

   
   
   
   This animated graphic shows Venus and Mercury over a period of several days from March 16th to the 29th of March. The time is set for 7:15 pm CDT and in the first several frames the planets are first shown as they would appear at 7:15 pm, then I added labels, then their respective orbits. To make the animation easier to see I also turned off daylight, and then finally the labels were turned off then back on at the end.
   
   
   
   

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.

Mercury At Eastern Elongation

orbital-positions    On Thursday March 15th Mercury, the innermost planet, will reach its orbital position known as greatest eastern 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 – from superior conjunction, behind the Sun, out to the left (east) from the Sun to eastern elongation, then reverse and move westward through (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!

   Currently Mercury is visible over the south to western horizon at sunset shining with an apparent magnitude of -0.14. About 3o from Mercury is the planet Venus with a much noticeable apparent magnitude of -3.91.

   
   
   
   
   

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.

Mercury at Eastern Elongation

orbital-positions    On Friday November 24th Mercury, the innermost planet, will reach its orbital position known as greatest eastern 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 – from superior conjunction, behind the Sun, out to the left (east) from the Sun to eastern elongation, then reverse and move westward through (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!

   Currently Mercury is visible over the south to southwestern horizon at sunset shining with an apparent magnitude of -0.27. About 3o above Mercury is the planet Saturn with an apparent magnitude of 0.50.

   
   
   
   
   

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.

Mercury at East Elongation

orbital-positions    On Sunday December 11th Mercury, the innermost planet, will reach its orbital position known as greatest eastern 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.
click on animated graphic to see it larger    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!
   This animated graphic shows Mercury at its eastern elongation and its orbital path. The horizon is removed in one graphic so Mercury’s orbit around the Sun could be visualized better.

   
   
   
   

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.

Mercury at Eastern Elongation

orbital-positions    On Monday April 18th Mercury, the innermost planet, will reach its orbital position known as greatest eastern 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!
   In less than a month, on May 9th, Mercury will move into inferior conjunction as it crosses the ecliptic moving south setting up a transit by Mercury across the Sun.


   Currently Mercury is very visible shining at nearly 0 magnitude over the western horizon at sunset.

   
   
   
   
   

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