Tag Archives: Spica

Inner Planets on the Move

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   This past month, November, the inner planets Mercury and Venus were very visible in the early morning skies before sunrise. Both of the planets were at or near their respective western elongation. Venus was there during August and Mercury reached its western elongation on November 10th.
   What I wanted to capture was the daily change in the position of Venus as it passed the star Spica in Virgo the Harvest Maiden. Venus moves about 1.6o each day so its eastward motion should be obvious after a day or so. It was – it is!. Mercury, if you are wondering, moves about 4o each day.
   Both inner planets were somewhere around their maximum separation from the Sun – as we see it the inner planet is to the right side of the Sun, or toward the west.
   The series of pictures were taken from two locations near my house. One is from an empty lot near U.S. Highway 50 looking east. The other pictures are from somewhere along the street I live on! The first picture was taken at Legacy Park and includes the ISS orbiting over my location.


   
   
   

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Venus – Spica Conjunction

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   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

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   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

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   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

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   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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Saturn Corrects Its Reversal

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   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

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   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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Virgo Grabs for a Croissant – or is it Crescent?

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   Saturday August 22nd the 4-day old waxing crescent Moon will be about 4-5o from the bluish-white star Spica in the constellation Virgo the Harvest Maiden. Spica, from mythology, is described as the bundle of grasses (wheat, oats ?) in her hand – which is appropriate for something representing agriculture.
   Rising in the east is a pair of outer planets, Jupiter and Saturn.

   
   
   

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Moon-Venus-M35 Conjunction

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   Saturday morning August 15th the thin 25-day old waning crescent Moon will be about 2-3o from the inner planet Venus, and about 3-4o from the open star cluster M-35. All three are located near the feet of the Gemini Twins.
   The contrast in apparent magnitudes is very striking with the Moon shining at -10.7 compared to the -4.3 apparent magnitude of Venus. M-35, with an apparent magnitude of 5.3 will be difficult if not impossible to see with the bright Moon and Venus nearby. Under other conditions M-35 is visible to the naked-eye under dark skies. All three rise 2-3 hours before sunrise local time and will easily fit within the field of view of binoculars. To see just Venus and M-35 wait until tomorrow after the Moon has moved further east, is a thinner crescent and less bright. However Venus will have also moved a bit more than 1o east as it orbits along.
   If you can see the crescent Moon after sunrise it may even be possible to see Venus during the daytime using the Moon as a guide for where to look.

   
   

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August Moon at Ascending Node

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   Friday August 14th the thin 25-day old waning crescent Moon will be crossing the plane of the ecliptic moving north. This is known as the ascending node, one of two intersections the Moon’s orbital path has with the ecliptic. The ecliptic is actually the Earth’s orbit, and the Moon’s orbit is inclined about 6o from the ecliptic. So there are two node intersections, the ascending and descending nodes.
   On the morning of the node crossing the thin waning crescent Moon is positioned about midway between the reddish Aldebaran to the west, and the inner planet Venus to the east.
   Does our Moon actually go around the Earth as many graphics show? 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*
*Click here to read my 2006 Scope on the Sky column “The Real Shape of the Moon’s Orbit”. (PDF)
   
   
   
   
   
   
   

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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