Moon, Mercury, Venus trio-- close!

Event Date: December 11th

Time: 6:30 AM

Brief

Hope for clear skies this morning, shortly before Sunrise.  Joining Venus and Mercury, is the Moon, as an old, waning crescent.  This is a good morning to also imagine the orbits of each solar system body relative to each other, although we only see the solar system bodies below.  The Moon is not in line with the two planets, yet forms a small triangle within a 7º field.  In image one, an 8º field is used to keep the planets away from the circumference; that is folliowed by one showing the three bodies zoomed out.  

click on image to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

Detailed

At only 4% illuminated, the Moon will not be easy to see until high enough, and while still dark enough.  That is, can you see our satellite as it emerges from atmospheric pollution, and as the planets join it before twilight interferes?  Mercury rises 1 hour, 25 minutes before the Sun, still far enough north of it for an impressive apparition; this despite being past greatest elongation.  Venus continues to approach superior conjunction, yet also far enough north to rise a little over 2 hours before the Sun this morning.  As for the Moon, it of course is moving east towards the Sun each day during waning, yet rises shortly before Merucry and not long after Venus.

   This triangular configuration is nothing new, as we see several consisting of this specific trio each decade; on average, about two a year, depending how far Venus is from the Sun in separation at the time and Mercury's elongation.  However, this is a good time to view all three together; while high enough above the horizon to view, Mercury is at magnitude -0.5, being brighter than only two stars in the sky in apparent magnitude: Canopus (-0.6) and Sirius (-1.5) being the only ones brighter in apparent magnitude.  The former is too far south on the celestial dome to see from most latitudes in the US, and only makes a small arc above it for most southern states (Florida and Texas).  Sirius is a favorite seen from both hemispheres, albeit briefly from far-north latitudes.