April Moon at Perigee

   The Moon reaches perigee, (minimum distance from Earth), this month on Friday March 3rd. At that time the Moon will more or less be at a distance of 28.17 Earth diameters (359,327 km or 223,275 miles) from the Earth.

   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*

   On the day of the perigee Moon the 1.5-day young thin waxing crescent Moon is above the western horizon at sunset local time and is near Dwarf Planet Ceres and the Pleiades open star cluster.

   *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 go to bobs-spaces.

Crescent Moon Near Venus

   Sunday morning April 23rd the thin 26-day old waning crescent Moon will rise to right, west, from the inner planet Venus. The two will be about 6o apart and will easily fit within the field of view of 7×50 binoculars.

   
   
   

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.

Moon Near Saturn


   Sunday morning, April 16th the 19-day old waning gibbous Moon will rise near the planet Saturn. The two will be within the 7o field of view of 10×50 binoculars and will be easily seen over the eastern to southeastern horizon in the hours before the sun rises.
   
   
   

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.

Uranus at Solar Conjunction

uranus-at-conjunction-from_earth
   Friday April 14th the outer planet Uranus will be at solar conjunction. This is a position where Uranus is on the opposite side of the Sun as seen from Earth. All of the planets, as viewed from Earth, will reach solar conjunction at some point during their orbit around the Sun. For the two inner planets, Mercury and Venus, this is known as superior conjunction rather then simply conjunction as it would be for the outer planets.

   
   
   

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.

Full Moon Near Jupiter and Spica


   Monday evening April 10th the full Moon will be about 3o from Jupiter and about 5o from the blue-white star Spica in Virgo the Harvest Maiden as the trio rises in the east.

   
   
   
   
   
   

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.