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 30° south. 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 morning apparition of Mercury (blue track) is the best one for observers at 30° south latitude. Beginning as a fifth-magnitude object low in the east in early February, it brightens as it climbs to an altitude of over 26° and ends the apparition in mid-April at magnitude −2.1. The next morning apparition from mid-June to the beginning of August (pink track) is not as favourable although Mercury still manages a respectable 18° of altitude at the beginning of July. The final dawn appearance of Mercury in October and November (green track) is the worst with the planet barely reaching 9° above the eastern horizon.

The first apparition of 2021 (blue track) completes the last one of 2020 and is the least favourable evening appearance of the year, with Mercury only reaching an altitude of 12.5° in mid-January. The April–July apparition isn't much better, with Mercury attaining 13° at its maximum height above the northwestern horizon. However, the third apparition (green track) from August through to October provides an excellent opportunity to catch a glimpse of this elusive planet. Mercury appears in early August low in the west-northwest and soars to a height of 26° by mid-September before descending back toward the western horizon. As with all evening apparitions, Mercury is brightest at the beginning of its appearance and dims as time goes on, ending the apparition as a sixth-magnitude object low to the horizon. The final apparition occurs in December (orange track), with Mercury climbing to an altitude of 14° by the end of the year. It continues to ascend into next year.

Venus

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

Venus spends the first three months completing the morning apparition of 2020. The bright planet starts the year at a magnitude of −3.9 and an altitude of 16.7° and dims slightly as it appears ever lower in the eastern sky. It is lost to view well before the end of March.

Venus occupies the western skies after sunset for most of the year. The evening star appears very low in the west at the end of March and begins a slow climb in what eventually becomes a superb apparition for southern hemisphere observers. The end of October finds Venus dominating the scene after sunset, nearly 46° above the horizon and shining at a brilliant magnitude −4.4. The planet reaches its maximum brightness (−4.7) in early December by which time it is already moving back toward the Sun. Venus is only 7.8° above the horizon at the end of the year, with the apparition finishing in early 2022.

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.