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. In 2021, Mercury inhabits the morning skies three times and the evening skies four.

The first appearance of Mercury in the morning sky (blue track) is also the best, with the zero-magnitude planet soaring to an altitude of 22° in early March. It has a long, slow decline afterwards, brightening to magnitude −2.1 as it disappears below the horizon in mid-April. The second morning apparition (pink track) is also quite good. Mercury reaches a height of 20° above east-northeastern horizon in early July. As is always the case with morning apparitions for Mercury, the tiny planet begins the apparition around fifth- or six-th magintude and ends at a bright −2. The final morning apparition of October–November (green track) is the poorest of the three but Mercury still manages nearly 17° of altitude before the end of October.

The first evening apparition of Mercury (blue track) continues from last year. The bright planet manages a maximum altitude of 17.8° above the west-southernwestern horizon in late January before quickly vanishing in early February. The second apparition (pink track) is the best one for observers at 10° north latitude. Mercury reaches an altitude of 20° or more for almost two weeks in mid-May and is a zero- or first-magnitude object during this time. However, it dims quickly afterwards as it plummets back toward the sunset horizon. The evening apparition of August–October (green track) is also good, with Mercury again attaining 20° in early September. It shines at zero magnitude at this time but fades to fifth magnitude by early October. The last evening appearance of Mercury (orange track) occurs in December but the tiny planet will not reach its maximum altitude until early next year.

Venus

After a short tenure as the morning star, Venus moves to the evening skies for the remainder of the year.

The morning star from 2020 completes its appearance in the dawn sky during the first three months of the year. It is highest and brightest on the first day of January and appears closer to the horizon every morning until it disappears in late March, only to reappear in the evening sky.

The evening star appears low in the west at the end of March in what is a decent apparition. Venus gains a little bit of altitude every evening until mid-November, ultimately reaching nearly 38° in height. It then drops precipitously as it heads to inferior conjunction early next year. The bright planet ends December just 12° above the horizon but very bright at magnitude −4.3.

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.