Venus – Spica Conjunction


   Over the next few days the inner planet Venus will be moving eastward as it passes the blue-white star Spica in Virgo the Harvest Maiden. This animated graphic is set to 1-day intervals and shows the morning sky from November 16th to the 20th.


   On Monday morning November 16th Venus will be the closest to Spica for a conjunction that has the two separated by about 3-4o. A few degrees, 13o, further east (lower) is the other inner planet Mercury.

   
   
   

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Moon – Inner Planets & 1 Star

   The waning crescent Moon, as it moves eastward toward new Phase on the 14th, passes by the two inner planets Venus and Mercury. Yesterday the Moon was west from the planets and after 24 hours of revolution the Moon has moved to between the two planets this morning.

   
   
   

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Mercury at Western Elongation – See it in the Morning Skies

   On Tuesday November 10th Mercury, the innermost planet, will reach its orbital position known as greatest western elongation at 19.1o. At that moment Mercury, the Sun, and the Earth, would be arranged in something close to approximating a right angle as this graphic shows. Even though it sounds confusing at western elongation for either Mercury or Venus the inner planet will be to the right of the Sun as we view them, meaning that at western elongation an inner planet rises in the east before the Sun rises. And at eastern elongation with the inner planet on the left side of the Sun the inner planet follows the Sun across the sky setting after the Sun sets.

   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!

   There is a lot to see and a few things you cannot see on the morning of Mercury’s western elongation. Going by relative apparent magnitudes Mercury (-0.52), Venus (-3.99), Spica (0.96), are all easily visible as bright to very bright star-like objects. The 24-day old waning crescent Moon shines at a much brighter apparent magnitude of (-11.52).

   
   
   
   
   

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A Missouri Morning with the ISS

   This morning opened up with a colorful sunrise as the background for the ISS as it orbited toward the southeast. High overhead toward the south was the near last quarter Moon brightening the sky in that direction. However this was not a morning for taking pictures of the Moon.
   Right on time the ISS appeared over the northwest horizon and steadily moved past Polaris, the North Star, then past the Big Dipper’s Dipper heading toward the star Arcturus in Bootes the Herdsman. On its way toward the southeastern horizon the ISS went past Venus, Mercury and the star Spica in Virgo the Harvest Maiden.
   While waiting and taking random pictures in different directions I managed to catch a Taurid Meteor!

   
   
   

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Mercury at Inferior Conjunction

   Sunday October 25th 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 south of the ecliptic, by about 1.91o.

   
   
   

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Mercury at Eastern Elongation

orbital-positions    On Thursday October 1st 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!

   The planet Mercury is currently over the western horizon at sunset local time and will remain visible for most of the month.

   
   
   

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Saturn Corrects Its Reversal

   On Tuesday September 29th in a move that comes about annually, Saturn will once again reverse its direction from moving toward the west to moving toward the east.
   Since around May 11th Saturn has appeared to be moving westward (toward the right) rather then toward the east. This happens as the faster moving Earth catches up with and then passes by Saturn. This apparent westward motion of Saturn is known as retrograde motion and for Saturn it’s retrograde motion comes to an end during mid-September when Saturn resumes its normal orbital motion toward the east, or to the left as we view Saturn from the Earth.
   Since retrograde is a reference to motion and means backward or reverse motion, then the opposite of retrograde would be prograde motion. So it would be correct to describe Saturn as having resumed prograde motion. However you would probably get a blank look from those you say this to! So stick with “direct motion” or just say that Saturn orbits the Sun to the east as we see it from Earth.

   Saturn is located over the southern horizon after sunset local time. It is about 7-8o to the east from Jupiter.

   
   
   
   

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Moon – Jupiter & Saturn Conjunctions

   The waxing gibbous Moon, over the next two evenings (September 24th and 25th, will pass by two of the giant outer planets. The Moon will pass within about 2-3o from Jupiter and about 1-2o from Saturn.
   Off toward the eastern horizon is the innermost planet Mercury and the bluish-white star Spica in Virgo the Harvest Maiden.


   
   
   

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September Moon at Descending Node

   Wednesday September 23rd the 7-day old first quarter Moon crosses 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 date of the descending node the first quarter Moon will be about 20o to the east from the heart of Scorpius the Scorpion, the reddish star Antares, and about 15-16o west from Jupiter.
   Mercury and Spica are still a couple of degrees apart but low above the horizon as the Sun is setting.

   
   
   
   
   

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Mercury- Spica & Moon – Antares

   Tuesday September 22nd shortly after sunset local time look toward the western horizon for the innermost planet Mercury to be about 1o from the bluish-white star Spica in Virgo the Harvest Maiden. The two should make for an interesting comparison in apparent magnitudes with Spica at 0.96 and Mercury with a -0.01 apparent magnitude.
   The nearly first quarter but still waxing crescent Moon will be about 7-8o from the reddish star Antares in Scorpius the Scorpion. Both are positioned over the southern horizon.

   
   
   

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