SkyEye

What is an Apparition?

An apparition of a planet is the period during which it is visible, beginning and ending with solar conjunction. In the cases of the inferior planets Mercury and Venus, it is the time between inferior and superior conjunction (morning apparition) and the time between superior and inferior conjunction (evening apparition). Because inferior planets are always near the Sun, they only appear in the east before sunrise and the west after sunset.

Below are a series of diagrams showing the morning and evening apparitions of Mercury and Venus as observed from latitude 50° north. The planet is shown on the 1st, 6th, 11th, 16th, 21st and 26th days of each month with the current year's positions shown in bright white. The path may extend from the previous year or into the next.

Mercury

Mercury undergoes several morning and evening apparitions every year. This year finds Mercury in the morning skies four times and the evening skies thrice.

The final morning apparition of 2017 becomes the first morning apparition of 2018 (blue track) but Mercury is already heading back toward the southeastern horizon. The second apparition (pink track) in April, May and June is almost impossible to observe, primarily due to the low altitude (less than 10° above the horizon) of the planet. The third apparition (green track) is the most favourable, with Mercury approaching 15° in altitude and brightening from magnitude +5.0 to −1.8. The final morning apparition at the end of the year (orange track) is nearly as good.

The first evening apparition (blue track) begins in mid-February and continues throughout March. This is the best evening apparition for observers in northern temperate latitudes, with Mercury reaching a maximum altitude of 16.5° and slowly dimming from a bright magnitude −1.7. Mercury next appears after sunset in June (pink track). Although the planet doesn't get as high as it did in March, it is brighter for longer. The final evening apparition of the year (green track) begins in September but it is all but impossible to observe. Mercury is relatively bright for much of the apparition but always remains within 5° of the horizon.

Venus

Venus is primarily an evening sky object in 2018.

The morning apparition of 2017 ends in the opening days of this year (blue track) but the planet is so close to the horizon that it is unobservable. Venus appears for a second time in the morning sky in November (pink track), where it remains until August of next year. Venus reaches its maximum magnitude of −4.7 in late November and early December.

Following superior conjunction at the beginning of the year, Venus appears very low to the southwestern horizon in mid-January. This is a disappointing apparition for observers in northern temperate latitudes, with Venus reaching only 23° in altitude. Venus is at its brightest in late September when it is already very low in the sky.

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.