Mercury at Superior Conjunction

mercury at superior conjunction   Thursday July23rd at 19 UT (2 pm CDT) the innermost planet Mercury reaches superior conjunction – on the opposite side of the Sun from the Earth.
   Mercury is not visible while in conjunction with the Sun but within the next week or so Mercury will reappear on the east side of the Sun and start becoming visible over the western horizon at sunset.

   
   
   
   
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   Saturday May 30th at 17 UT (12 pm CDT) 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.

mercury at inferior conjunction   While at inferior conjunction Mercury is not 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). This past May 23rd Mercury was at its descending node, and for those thinking ahead Mercury crosses the ecliptic moving north (ascending north) next month on June 24th.

   
   
   
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.

Another Two for One

   Saturday evening around an hour or so after sunset local time three planets will be visible above the southwestern to western horizons. Lowest is the innermost planet Mercury. It is actually best viewed a little earlier as at the time shown in this graphic Mercury is just about to set. On the other hand Venus shining with an apparent magnitude of -4.15, and much higher above the horizon Jupiter with a -2.15 apparent magnitude would be difficult to miss. Both of these planets are each near an open star cluster. Near enough so that each of these planet/star cluster pairs will fit within the field of view of binoculars.


   Venus is within 2o from the open star cluster M-35. This is a grouping of several hundred stars located at a distance of around 2800 light years that shines with a combined apparent magnitude of between 5 and 6. This puts it right around the naked eye limit but visible with binoculars. Jupiter is within 6-7o from the open star cluster M-44, or the ‘Beehive Cluster’. This easily seen star cluster has an apparent magnitude of around 3.5 and is composed of 300 stars located at a distance of around 155 light years.

   
   
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.

Mars-Mercury Close Conjunction

22apr-bino   Wednesday evening April 22nd at sunset the inner planet Mercury and the outer planet Mars will be within 1-2o from each other as they set over the western horizon. The two should make for a nice view with binoculars as this graphic shows. Actually the two will be close to each other for the next several evenings. However Mars is setting earlier each night while Mercury is moving eastward away from the Sun and Mars. Compare the the relative orbital speeds: Mercury moves around 4o each day while Mars less than 1o. For another comparison look at their relative brightness. Mars has an apparent magnitude of 1.42 compared with the -1.1 for Mercury.

   Viewing the two planets may be a challenge as they are both low above the western horizon at local time for sunset.

   
   
   
   
   
   
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.

Interior and Inferior

inner-planets-positions

   Friday January 30th at 14 UT (8 am CST) the innermost planet Mercury reaches inferior conjunction. This is one of four points along an inner planet orbit, and at inferior conjunction Mercury is between the Earth and the Sun – like a new Moon phase.

   
   
   
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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.

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.

Mercury Watch

Mercury 1 to 13 February 6 pm CST

Mercury 1 to 13 February 6 pm CST

   This evening and for the next several the innermost planet Mercury will be visible at sunset above the southwest horizon as the banner graphic at the top of the page shows. Mercury reaches inferior conjunction, between the Sun and Earth, on the 15th and between now and then Mercury will be moving west toward the Sun. Each evening at the same time Mercury may be observed to be lower above the horizon as it moves toward inferior conjunction as this animated graphic is showing.
You might also notice that in each frame (day) the Sun is a little higher at the same time. This is the Sun’s apparent daily eastward motion along the ecliptic. This is also why it takes such a relatively short time for Mercury to orbit from eastern elongation to inferior conjunction. Combine the Sun’s nearly 1 degree/day east with Mercury’s westward orbital motion of 4 degrees/day and it is easy to see why the ‘closing rate’ is so fast.
mercury-phases-ani     Another interesting and observable change is Mercury waning from a small gibbous phase to a larger crescent phase as this small animated graphic is showing. It shows the planet from the 1st to the 15th when Mercury reaches inferior conjunction.

   
   
   
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.