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 10° 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 first morning apparition of 2018 (blue track) is a continuation of the final morning apparition of 2017. Mercury is never higher in the sky than it is on the first day of the year, and it ranges in magnitude from −0.3 to −1.5 by the time it disappears below the southeastern horizon. The second morning apparition (pink track) is nearly as good. Mercury first appears above the horizon in April, eventually rising to an altitude of 21°. The planet is somewhat fainter at the start of the apparition, only sixth magnitude, but it eventually gets as bright as magnitude −2.2 before it vanishes in the northeast. The next apparition in August and September (green track) is the poorest for this latitude although Mercury still manages a respectable 17° of altitude. The final apparition of the year (orange track) is similar to the first and continues into 2019.

The first evening apparition (blue track) is also the worst evening apparition for this latitude. It begins in mid-February with Mercury shining brightly at magnitude −1.7 but from mid-March, the planet dims rapidly, approaching fifth magnitude before it disappears in the west. The June–July evening apparition is the best, with Mercury rising to an altitude of 24°. The planet begins at a brilliant −2.3 magnitude but dims throughout the apparition. The final evening appearance begins in mid-September and continues to almost the end of November. Although Mercury does not get as high as in the previous apparition, it does remain relatively bright for most of its final apparition in the western skies.

Venus

Venus is primarily an evening sky object in 2018.

The first morning apparition of 2018 (blue track) is unobservable, with Venus spending only a few days just above the horizon. Reappearing a second time in late October/early November (pink track), the planet races high into the dawn sky, reaching a maximum altitude of 45° just before the end of the year. It attains its brightest magnitude of −4.7 in the latter part of November and the early part of December.

Venus appears in the southwest in mid-January, eventually rising to an altitude of 39° and putting on a fine show as the evening star. It reaches its maximum magnitude of −4.6 in late September when it is still high in the sky after sunset. Venus rapidly plummets toward the southwestern horizon in October, reappearing in the morning sky the following month.

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.