SkyEye

Solar System Phenomena - 2018 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 in the morning skies four times and the evening skies thrice.

13 December2017inferior conjunction
01 January2018greatest elongation west 22.6°
17 Februarysuperior conjunction
15 Marchgreatest elongation east 18.4°
01 Aprilinferior conjunction
29 Aprilgreatest elongation west 27.0°
06 Junesuperior conjunction
12 Julygreatest elongation east 26.4°
09 Augustinferior conjunction
26 Augustgreatest elongation west 18.3°
21 Septembersuperior conjunction
06 Novembergreatest elongation east 23.3°
27 Novemberinferior conjunction
15 Decembergreatest elongation west 21.2°
30 January2019superior conjunction

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Mercury greets the new year in the southeast at dawn. This first apparition of 2018 (blue track) finishes the last apparition of 2017. However, the best morning apparition is the second (pink track) which occurs from April to the beginning of June. Mercury attains an altitude of 26° and slowly brightens from sixth magnitude to -2.3. The next apparition (green track) is the poorest although the planet briefly tops 11° in altitude. The final morning apparition begins in late November and is similar to the first one of the year. Mercury is already heading toward the southeastern horizon by the end of the year and the beginning of the first morning apparition of 2019.

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The first evening apparition (blue track) begins in mid-February and is poor for this latitude. It is the second evening apparition (pink track) that is particularly good. It begins in early June and ends in early August, with Mercury reaching an altitude of nearly 24° above the northwestern horizon. It is brightest at the beginning of the apparition (magnitude -2.1), gradually fading to sixth magnitude over the course of two months. The final evening apparition in September-October-November is also favourable, with Mercury getting nearly as high above the horizon (southwest rather than northwest) as its previous appearance. However, Mercury does not get quite as bright this time.

Venus

Venus is primarily an evening sky object in 2018.

25 March2017superior conjunction
30 Junegreatest elongation west 45.9°
09 January2018superior conjunction
17 Augustgreatest elongation east 45.9°
26 Octoberinferior conjunction
06 January2019greatest elongation west 47.0°
17 Augustsuperior conjunction

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Technically there is a morning apparition at the beginning of the year (blue track) but Venus is too close to the southeastern horizon to be seen. It reappears around the time of the October inferior conjunction (pink track) and rises steadily in the east, reaching its maximum brightness in early December and getting to an altitude of over 36° by the end of the year. It continues to climb into next year's morning apparition.

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This is an excellent apparition of the evening star, with Venus reaching a maximum altitude of nearly 45° in late August. The planet attains its maximum brightness in late September by which time it is starting to descend toward the southwestern horizon.