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.
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.
Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.