SkyEye

Solar System Phenomena — 2021 Apparitions of the Inferior Planets from Latitude 50° North

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 50° 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.

20 December2020superior conjunction
24 January2021greatest elongation east: 18.6°
08 Februaryinferior conjunction
06 Marchgreatest elongation west: 27.3°
19 Aprilsuperior conjunction
17 Maygreatest elongation east: 22.0°
11 Juneinferior conjunction
04 Julygreatest elongation west: 21.6°
01 Augustsuperior conjunction
14 Septembergreatest elongation east: 26.8°
09 Octoberinferior conjunction
25 Octobergreatest elongation west: 18.4°
29 Novembersuperior conjunction
07 January2022greatest elongation east: 19.2°
23 Januaryinferior conjunction

The morning apparitions of Mercury in 2021 as seen from latitude 50° north.

The first morning apparition (blue track) is also the worst for observers this far north. Appearing low in the east-southeast at the beginning of February, Mercury never gets higher than 8° above the horizon and is unobservatoble in early April. The next apparition (pink track) is better, with third-magnitude Mercury appearing in the northeast toward the end of June, brightening to zero magnitude as it reaches a maximum altitude of over 11° in early July before disappearing later that month. However, the best appearance of Mercury in the dawn sky occurs in the months of October and November (green track). Only fifth magnitude when it first appears low in the east in mid-October, the tiny planet quickly brightens, reaching negative magnitudes before attaining a maximum altitude of nearly 16° before the end of the month. It continues to brighten as it heads back toward the southeastern horizon and superior conjunction on 22 November.

The evening apparitions of Mercury in 2021 as seen from latitude 50° north.

The final apparition of 2020 segues into the first evening apparition of this year (blue track), with Mercury appearing very low in the southwest at the beginning of January. This is only a fair appearance of the tiny planet, with it reaching 13.7° in altitude two days after greatest elongation east. The best evening apparition at latitude 50° north occurs in April–June (pink track) when Mercury reaches an altitude of over 17° in May. The planet appears in late April shining at magnitude −2.2 but slowly dims, ending as a fifth-magnitude object when it disappears from sight in early June. The next apparition (green track) occurs in August and September and is virtually unobservable due to the low altitude (not even 6°) of Mercury throughout. The final appearance of Mercury takes place at the end of December (orange track) where the planet continues to climb in altitude into next year.

Venus

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

03 June2020inferior conjunction
13 Augustgreatest elongation west: 45.8°
26 March2021superior conjunction
29 Octobergreatest elongation east: 47.0°
09 January2022inferior conjunction

The morning apparitions of Venus in 2021 as seen from latitude 50° north.

The excellent 2020 morning apparition of Venus draws to a close during the first two months of 2021, with the morning star already low in the southeast and appearing closer to the horizon every morning. At an altitude of 9.7° on the first day of the month and shining at magnitude −3.9, it is neither higher nor brighter in the dawn sky this year.

The evening apparitions of Venus in 2021 as seen from latitude 50° north.

The appearance of Venus as the evening star is a major disappointment this year. It appears in the west after sunset in April, reaching a paltry altitude of 12.7° in late June before descending again. It regains this lost altitude and more later in the year but never gets higher than 14.8°. It increases in magnitude throughout its evening appearance, beginning at −3.9 in April and attaining −4.7 in early December, around the time it is highest in the sky. Venus descends back toward the horizon from mid-December, with the apparition ending in January 2021.

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.