Mercury at Superior Conjunction

   Monday August 17th the innermost planet Mercury reaches superior conjunction. At superior conjunction Mercury will be on the opposite side of the Sun. The graphic to the right shows the planet positions relative to the Earth and Sun for both inner planets and outer planets.
   While at this superior 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 superior conjunction Mercury is 6.96o North and is about as far north of the ecliptic as it can get.

   Speaking about inner planets here is the other inner planet, Venus, and the 27-day old waning crescent Moon this morning.

   
   
   

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Uranus at Western Quadrature – 2020

   Sunday August 2nd the position of the planet Uranus, with respect to the Earth and the Sun, places this ringed planet at what is called western quadrature. At that orbital position Uranus, and actually any outer planet, is at a 90 degree angle from the Earth as this graphic shows, and also this graphic. Think third quarter Moon as that is a fair comparison of the relative positions of Earth, Sun, and Uranus.
    At western quadrature Uranus leads the Sun across the sky from east to west as the Earth is rotating, meaning that Uranus rises before the Sun and also sets before the Sun.

   
   
   This is a short video clip from a much longer video that I made as part of a live musical performance called “Orbit” at the Gottleib Planetarium in Kansas City Missouri during May 2011.

   
   
   

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A Saturday *2fer

   Saturday August 1st there will be two opportunities for planet and Moon viewing. (a ‘2fer’)
   On Saturday morning before the Sun rises watch for the innermost planet Mercury to be about 6-7o from Pollux, one of the two ‘twin stars’ of Gemini the Twins, as this graphic is showing. Venus, if you haven’t noticed, is shining very brightly higher above the southern horizon.
   Then Saturday evening after sunset look for the 12-day old waning gibbous Moon to be about 1-2o from the outer ringed planet Jupiter and about 4-5o from another outer ringed planet, Saturn.
   
   
   
   
   *2fer – suggesting that it is possible to get two instead of one (2 for 1) of whatever is being got.
   
   
   

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Mercury at Western Elongation

   On Wednesday July 22nd Mercury, the innermost planet, will reach its orbital position known as greatest western elongation at 20.1o. 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 (0.33), Venus (-4.43), Mars (-0.89) are all easily visible as bright to very bright star-like objects. On the other hand those not seen with the naked-eye but are still above the horizon in the morning skies include: Uranus (5.80), Eris (18.64), Neptune (7.84), Ceres (7.40)

   
   
   
   
   

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Mercury at Inferior Conjunction

   Wednesday July 1st 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 5.47o.

   
   
   

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Thin Moon on the Move

   Sunday June 21st, on the other side of the Earth from the U.S.A., the new Moon will be passing between the Earth and the Sun giving that side of the world an annular solar eclipse.
   About 1/2-day later the just past new Moon, an 0.80-day young thin waxing crescent Moon may be seen just above the western horizon at sunset local time. If you see the Moon look closely for a star-like object just to the left from the Moon. This is the inner planet Mercury.
   If you miss the Moon and Mercury on Sunday evening wait until Monday evening June 22nd to see the still thin 1.85-days old waxing crescent Moon near one of the Gemini ‘Twin’ stars, Pollux.
   Not had enough? On Tuesday June 23rd the 2.80-days young waxing crescent Moon will be near M44, the Beehive Cluster.
   Any of these conjunctions will look great in binoculars.

   
   
   

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Mercury at Eastern Elongation

orbital-positions    On Thursday June 4th 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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June Apogee Moon

   Our Moon reaches perigee, (closest to Earth), for this orbit, on Wednesday June 3rd. At that time the Moon will be at a distance of 28.56 Earth diameters, 226,406 miles (364,366 km) from the Earth.

   On the day of the perigee Moon the 13.3-day old waxing gibbous Moon rises a couple of hours before the Sun sets placing the Moon over the southeastern horizon around mid-evening.

   Does our Moon actually go around the Earth as this graphic shows? 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)

   
   
   
   
   
   

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Moon on the Move

   Over the next several days the Moon, as it waxes toward first quarter, will be moving toward the east and as it does the Moon will pass by several of the brighter stars along the Moon’s orbital path. This will take the Moon near Pollux, one of the Gemini ‘Twins’, and then past Regulus, the ‘Heart’ of Leo the Lion. On the 27th you may be able to see the open star cluster, M-44, or also known as the Beehive Cluster.



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Thin Waxing Crescent Moon Near Venus – Mercury

   Saturday evening May 23rd look toward the western horizon for the very thin young 1.3-day old waxing crescent Moon. The Moon will be about 3-4o from the inner planet Venus and about 5-6o from the other inner planet Mercury. All three will easily fit within the field of view of binoculars and given the range of apparent magnitudes should make for a great view and even a picture.
   Apparent MagnitudesWaxing Crescent Moon: -8.42 Venus:-4.16 Mercury: -0.42
   
   
   
   
   
   

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