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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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.

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Jupiter at 15 Day Intervals

Jupiter at 15 Day Intervals (8 November – 8 May)

   A Backwards Jupiter, or when the giant planet starts retrograde motion. Tuesday December 9th the largest planet in our solar system, Jupiter, begins its retrograde motion. Retrograde motion is an apparent motion that the outer planets, relative to the Earth, have. It is an apparent motion that looks as if the outer planet stops it normal direct motion to the east and reverses direction to the west. After a period of time the apparent westward motion ends and the planet resumes its normal orbital path to the east. Retrograde motion happens as the faster moving Earth catches up with and then passes by the outer planet. It is during this time that the backward apparent motion happens.
   The two inner planets also have retrograde motion but it is a result of their orbit around the Sun and not the Earth passing them by. For approximately one-half of their orbit they move east, from western elongation through superior conjunction to eastern elongation. Then at eastern elongation the inner planet starts moving westward through inferior conjunction to western elongation.
   Read a little more about retrograde motion in my February 2012 Scope on the Skies column, drawkcab planets, in Science Scope Magazine.
Click on graphic to see it full size.

Click on graphic to see it full size.

   Where is Jupiter now? Jupiter is a few degrees west from the star Regulus in Leo the Lion. Jupiter rises around midnight local and is visible above the horizon the remainder of the night.

   
   
   
[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.

Venus and M-35

Click on graphic to see it full size.

Click on graphic to see it full size.

   Sunday morning, 20 July, the planet Venus will be within 2o from the open star cluster M-35, a fairly easy to see object with the naked-eye and binoculars in reasonably dark skies. Looking like an out-of-focus star M-35 is an open star cluster located near the feet of Castor, one of the Gemini Twins. M-35 consists of several hundred stars in a group spanning about 30″, about the size of the full Moon. M-35 shines at an apparent magnitude of around 4.5 as compared with the -4.0 magnitude of nearby Venus.

20july-bino   Adding to viewing is the other inner planet, Mercury, located about 6o down to the left from Venus as this graphic shows.

   
   
   
[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 Inferior Conjunction

orbital-positions   Thursday 19 June at 23 UT (6 pm CDT) the innermost planet Mercury reaches inferior conjunction. As the banner graphic at the top of the page shows, inferior conjunction of Mercury places Mercury between the Earth and the Sun – much like the position of the Moon at new phase. The graphic to the right shows the relative to the Earth and Sun position names for both inner planets and outer planets.

   The short video below, taken by the Mars Curiosity Rover, shows a transit of the Sun by Mercury as seen from the surface of Mars.

   
   
   
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.

¿dónde están Venus y Mercurio

   So where are Venus and Mercury?
   Friday, 1 November, these two inner planets will be at one of their four respective and specific locations along their orbital path around the Sun relative to the location of the Earth along its orbital path around the Sun.

orbits-above   Firstly, the innermost planet, Mercury, is not in transit as the banner graphic at the top of the page suggests. However Mercury is between the Earth and the Sun as this graphic shows. And, for either Mercury or Venus, when that happens the inner planet is said to be at inferior conjunction, but not necesarily in transit, or crossing directly in front of the Sun. Because the orbital paths of the planets are inclined away from the plane of the ecliptic, or the Earth’s orbit, the two inner planets ‘behave’ more or less as our Moon does when it reaches new Moon phase. When these objects come between the Earth and the Sun they are more often than not above or below the plane of the ecliptic and are therefore not in transit or eclipse. This is because of the planets inclination to the plane of the ecliptic. There are only certain times when the circumstances for a transit of either Mercury or Venus. The most recent and basically the last for a long time, was the Venus transit of 2012. I went to Tucson Arizona to view the event. And with my sister-in-law we joined a small group of like-minded people to view the transit from the observatory on the summit of Mt. Lemmon.

venus-orbit-ani   The other inner planet, Venus, has reached the point in its orbit around the Sun where Venus is as far ‘out’ from the Sun as we see the two near the horizon. This is measured as the angle between the Sun, Venus, and the Earth. This animated graphic shows Venus above the horizon then crossfades to show Venus in its current orbital position. This orbital position is called an elongation, and since Venus is in the evening sky to the east from the Sun, and setting after the Sun, ‘we’ would say that Venus is at greatest eastern elongation. At this elongation Venus is 47.1 degrees from the Sun.

Click here to go to the Mercury Chaser web page to see the Mercury elongation calculator.

Click here to go to the Seeing Venus in the Daylight web page, then scroll down to see the Venus elongation calculator.

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

Mercury Goes to Extremes

   mercury-aniToday the innermost planet Mercury reaches a point along its orbit around the Sun where it is more or less at a right angle from the Earth and the Sun, as the banner graphic at the top of the page shows. As viewed from above Mercury is to the right from the Sun, while from the backyard view on the Earth’s surface Mercury is also to the right from the Sun, or on its west side. This puts Mercury in the morning skies rising before the Sun rises and leading the Sun across the sky from east to west as the Earth rotates from west to east.

Earth, Inner Planets, and the Ecliptic

Earth, Inner Planets, and the Ecliptic

   From our backyard perspective we view the planets at more or less the same level because the 8 planets orbit the Sun on or close to the plane of the ecliptic, the Earth’s orbit extended outward from the Sun. So from this perspective the two inner planets appear to move back and forth, left to right to left, as they orbit the Sun. Today Mercury is at the ‘turning point’ on the right side of the Sun, which places Mercury at its greatest western elongation, or at its maximum angular separation from the Sun as seen from Earth. Today Mercury is approximately 20 degrees from the Sun. Due to its closeness to the Sun Mercury never gets more than around 30 or so degrees from the Sun which means that Mercury never rises or sets more than about 2 hours from the Sun. (The Earth rotates approximately 15 degrees every hour)

Click here to learn a little (or a lot) about the innermost planet Mercury from two MESSENGER web sites.

30 July - 5:30 am CDT

30 July – 5:30 am CDT

   While out observing Mercury look a little higher to the right for the planets Mars and Jupiter, plus some of the stars of the northern hemisphere winter season. While these two outer planets are also to the west from the Sun they do not have an elongation position as outer planets orbit the Sun beyond the Earth’s orbit rather than between the Earth and the Sun. Outer planets do reach a 90 degree angle relative to the Earth and the Sun but it is known as either east or west quadrature.

30 seconds worth of Mercury from the Orbit performance.

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

Venus Transits M-35

m35-zoom   If the sky is clear this evening, Wednesday 4 June, and you have a reletively level western horizon look for the planet Venus to be merged with the open star cluster M-35. Depending on the time of observation the planet will be transiting M-35 and its position relative to star cluster will be slightly different.
   Venus is doing a repeat of what Mercury did a few days ago as it passed close by M-35. Both of these two inner planets are currently moving eastward out away from the Sun coming from superior conjunction on the opposite side of the sun, toward their respective eastern elongation.

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