June Moon at Ascending Node

   Thursday June 27th the waxing crescent Moon will be crossing the plane of the ecliptic moving north relative to the ecliptic. 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 June 27th the 4-day old waxing crescent Moon will be with the constellation Leo the Lion, and the Moon will be located less than 1o from the heart of the Lion, the star Regulus. This should make for a great view with binoculars or through the eyepiece of a telescope.
   Just above the western horizon, possibly lost in the Sun’s glare, are two more planets – Mars and Mercury about 1o apart.

   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)

Read this very informative article about the Earth-Moon system and their orbital motions, written by Joe Hanson. “Do We Orbit the Moon?”

   
   
   

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.

Solar Eclipse of August 21


   I too have written some information about the solar eclipse, aka “The Great American Eclipse”, of August 21st. It is my attempt to compare two different views of the eclipse. One will be from within the path of totality where I will be, and the other in my hometown of Lee’s Summit Missouri just south of the path of totality by a few miles. As a result residents in Lee’s Summit, unless they drive north, will only see a partial eclipse with 99.986% of the Sun covered.
   So without further ado click here to go to Eclipsed Thoughts.

   
   
   

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.

Mercury at Superior Conjunction

mercury at superior conjunction
   Wednesday June 21st the innermost planet Mercury reaches superior conjunction – on the opposite side of the Sun from the Earth. For those that are curious, Mercury at superior conjunction is approximately 1.324 AU (123,073,489 miles; 198,067,580 km) from the Earth – the combined distance of the Earth to Sun distance plus the radius of Mercury’s orbit.
   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.

   
   
   

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.

They’re There!


   Tuesday morning, May 23rd the thin 26.7-day old waning crescent Moon will be surrounded by planets, most of which will be difficult to see given the time of day and how faint each one is. Except for Venus.

   
   
   

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.

Mercury at Western Elongation

19jan-mercury-east-elongation
   On Wednesday May 17th Mercury, the innermost planet, will reach its orbital position known as greatest western elongation at 25.8o. 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.
orbital-positions
   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!
   Mercury is visible in the morning skies before sunrise as this graphic shows.

   
   
   
   
   

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.

Mercury at Inferior Conjunction

orbital-positions   Thursday April 20th 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 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). In this situation Mercury is north of the ecliptic and 6 days away from its descending node on April 26th.

   
   
   

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.

Mercury Begins Retrograde Motion


   Sunday April 9th the innermost planet Mercury reaches a point in its orbit around the Sun where it moves toward the west as we view Mercury from the Earth. Typically when one hears this the term Retrograde Motion comes to mind, but with regard to an outer planet (relative to Earth). However while an outer planet’s retrograde motion is apparent the westward motion of an inner planet, Mercury or Venus, is very real. For Mercury or Venus retrograde motion begins around the time of eastern elongation and continues through inferior conjunction to around the time of western elongation. For Mercury this particular retrograde motion will end next month on the 17th.

   
   
   

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.