Friday September 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 Mercury, and Venus for that matter, appear to move out to the left (east) from the Sun for a period, then reverse and move westward between the Earth and the Sun to western elongation. From there the inner planet moves eastward going behind the Sun and eventually reappearing on the eastern side of the Sun for an eastern elongation. Repeat over and over – do not stop!
Mercury is currently visible as an ‘evening star’ over the western horizon at sunset. Saturn is also visible over the southern horizon west of Antares. Not bright enough to be visible are two of the dwarf planets in our solar system, Makemake and Haumea.
Click here to go to the Qué tal in the Current Skies web site for more observing information for this month.