SkyEye

The upper chart shows the path of Mercury across the background stars over the course of the year. Stars to magnitude +4.5 are shown with some fainter objects included to complete constellation patterns. The white circles represent the planet on the first day of the month and are scaled according to apparent magnitude. The faint paths before the first circle and after the last circle represent the planet's positions in December of last year and January of next. In general, the planet moves from right to left except when it's in retrograde and proceding in the opposite direction. As an inferior planet, Mercury never strays far from the Sun so it always begins and ends the year near the constellation of Sagittarius, located about one quarter of the way in from the left side of the chart.

The lower charts show how the appearance of Mercury changes over the year. Below each image is listed the date, the apparent magnitude, the apparent diameter of the disk (in arc-seconds), the geocentric distance (in au), the elongation from the Sun (in degrees) and the percentage of the disk which is illuminated. Like the Moon, Mercury exhibits a complete range of phases, from new to crescent to gibbous to full and back again. Because its synodic period is around four months, Mercury completes this phase cycle three times each year. Note how Mercury's magnitude varies widely, ranging (approximately) from −2.0 to +6.0 between conjunctions.

The closest planet to the Sun can be a difficult object to spot. It begins the year in the western sky after sunset but disappears in early February. After inferior conjunction it reappears in the morning sky between late February and late April, an apparition which favours observers in equatorial and southern latitudes. Mercury has a particularly close appulse with Jupiter during this time. Superior conjunction in mid-April heralds another appearance after sunset from April to mid-June. This is the best evening apparition for planet watchers in the northern hemisphere but everyone can enjoy the spectacle of Mercury and Venus only 0.4° apart at the end of May. Inferior conjunction follows, then Mercury swings back into the morning sky for the months of June and July. After superior conjunction at the beginning of August, another evening apparition begins which runs from August to early October. This appearance is almost unobservable from northern temperate latitudes but provides the best viewing opportunities for astronomers in the southern hemisphere. These observers will also be in the best place to see Mercury slip past Mars in mid-August. The final morning apparition runs from mid-October to late November which is the best dawn appearance of the planet for far northern latitudes; this is followed by the final evening apparition in December. The lunar occultation of 4 December may well be unobservable.

• Apparitions of the Inferior Planets from Latitude 50° North
• Apparitions of the Inferior Planets from Latitude 10° North
• Apparitions of the Inferior Planets from Latitude 30° South

Sources

The dates, times and circumstances of all planetary and lunar phenomena were calculated from the JPL DE406 solar system ephemeris using the same rigorous methods that are employed in the compilation of publications such as The Astronomical Almanac.