SkyEye

Solar System Phenomena — 2020 Apparitions of the Inferior Planets from Latitude 30° South

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. This year finds Mercury both in the morning and evening skies four times.

11 November2019inferior conjunction: transit
28 Novembergreatest elongation west: 20.1°
10 January2020superior conjunction
10 Februarygreatest elongation east: 18.2°
26 Februaryinferior conjunction
24 Marchgreatest elongation west: 27.8°
04 Maysuperior conjunction: anti-transit
04 Junegreatest elongation east: 23.6°
01 Julyinferior conjunction
22 Julygreatest elongation west: 20.1°
17 Augustsuperior conjunction
01 Octobergreatest elongation east: 25.8°
25 Octoberinferior conjunction
10 Novembergreatest elongation west: 19.1°
20 Decembersuperior conjunction
24 January2021greatest elongation east: 18.6°
08 Februaryinferior conjunction

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Mercury finishes 2019's last morning apparition (blue track) in the opening days of this year but it is already within 5° of the horizon and probably too low to spot. This is followed in March and April by the best morning apparition of the year (pink track) when Mercury gains an altitude of 27° in the east before sunrise. The winter apparition of July and August (green track) is not as favourable, with Mercury rising only 15° above the northeastern horizon. However, it is better than the final morning apparition in November and December (orange track) when the elusive planet gains only 10° in altitude. Morning apparitions are characterised by high magnitudes at the beginning of the appearance, brightening to brilliant negative magnitudes as it re-approaches the horizon and superior conjunction.

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After a short stint in the morning sky, Mercury quickly establishes itself in the west after sunset. However, the first evening apparition is a disappointment (blue track), with Mercury not quite reaching 11° in altitude. The planet soon vanishes by mid-February. The second evening apparition (pink track) is better, with Mercury appearing in the west-northwest in May and eventually rising to 17° in early June. However, it is the third evening apparition of August–October that is the most spectacular, with Mercury attaining an altitude of 25° at the beginning of October. The final apparition in the west (orange track) begins at the end of December and will be difficult to observe, with the tiny planet less than 7° away from the horizon. As far as brightness is concerned, evening apparitions behave in the opposite manner from morning apparitions. When found in the west, Mercury is brightest at the beginning of the apparition and virtually sixth magnitude by the end.

Venus

Venus spends the first part of the year as the evening star, then switches to dawn skies in early June.

17 August2019superior conjunction
24 March2020greatest elongation east: 46.1°
03 Juneinferior conjunction
13 Augustgreatest elongation west: 45.8°
26 March2021superior conjunction

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The morning apparition of Venus is a disappointment compared to 2019, only rising to 32° in late July. The morning star first appears in early June, quickly rising to its maximum altitude and then spending the rest of the year leisurely sinking back toward the horizon. It ends the year 17° high in the east. Venus is only magnitude −3.7 at the beginning of this apparition but soon brightens to −4.5 in early July. It dims back to −3.9 by year's end.

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The evening star is never higher in the western sky as it is on the first day of the year when it stands at an altitude of 27°. Shining at magnitude −4 in January, it slowly brightens as it gradually descends, reaching a maximum magnitude of −4.5 in late April. It is at this point Venus abruptly drops toward the horizon, disappearing in the west-northwest at the beginning of June.

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.