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The path of Jupiter against the background stars of Scorpius, Ophiuchus, Sagittarius, Capricornus and Aquarius from November 2018 to March 2022, with positions marked on the 1st of each month (click on the thumbnail for the full-size image). Periods when the planet was unobservable (i.e. when it was too close to the Sun, or passed behind it) are indicated by a dashed line; hence the planet became lost from view (in the evening sky) in early December 2019 and became visible again (in the morning sky) in mid-January 2020. The chart shows the changing shape of a planet's apparent looping formation as it moves through the zodiac. Jupiter crossed the ecliptic (the apparent path of the Sun through the zodiac constellations, which the Moon and planets follow closely) in a Southward direction in late February 2020, following which it described a zig-zag formation in Eastern Sagittarius. In the years on either side of ecliptic crossing the planet described a hybrid loop (half loop, half zig-zag); Northward-facing in 2019 and Southward-facing in 2021. The star map applies to observers in the Northern hemisphere (i.e. North is up); for the Southern hemisphere view, click here. The faintest stars on the map have an apparent magnitude of about +4.8. Printer-friendly versions of this chart are available for Northern and Southern hemisphere views. Astronomical co-ordinates of Right Ascension (longitude, measured Eastwards in hrs:mins from the First Point of Aries) and Declination (latitude, measured in degrees North or South of the celestial equator) are marked around the border of the chart. Click here to see a 'clean' star map of the area (i.e. without planet path); a printable version can be found here. Night sky photographs of the region, together with dates of the planet's passage of the brighter stars, can be seen below. Star names shown in yellow-green were officially adopted by the International Astronomical Union (IAU) in 2017 and 2018. The eight such star names shown on this chart were drawn from Chinese, Aboriginal, Polynesian, Persian and South African mythology (for more details see the IAU's Working Group on Star Names pages). |
The Position of Jupiter in the Night Sky:
2019 to 2022
by Martin J. Powell
Having spent the 2017-18 apparition in the constellation of Libra, the Balance, Jupiter entered Scorpius, the Scorpion, in mid-November 2018. The planet was out of view from Earth at this time, passing through superior conjunction (positioned directly behind the Sun as seen from the Earth) later that month.
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Jupiter imaged by Teruaki Kumamori (Sakai City, Osaka, Japan) on May 10th 2018 using a 14-inch (350 mm) Schmidt-Cassegrain reflector telescope and CMOS camera (Image: Teruaki Kumamori / ALPO-Japan) |
Jupiter
crossed into the non-zodiacal constellation of Ophiuchus,
the Serpent-Bearer, shortly before re-appearing in the dawn sky - rising
just ahead of the Sun
- in mid-December 2018. Jupiter reached
its Eastern stationary point in
mid-April 2019 before turning retrograde
(moving East to West) and describing its 2019 'hybrid' loop in South-eastern
Ophiuchus. Jupiter
reached opposition (its
closest and brightest orbital position in relation to the Earth for that year)
in mid-June 2019, positioned a few degrees North-west of the star 
Oph (Theta Ophiuchi, apparent
magnitude +3.2).
The planet continued its retrograde motion and reached its Western stationary point in
mid-August 2019. It
then resumed
direct
motion (West
to East), crossing the border into Sagittarius,
the Archer, in mid-November 2019. Jupiter headed out of view in the dusk twilight
during the second week of December 2019, marking the end of the planet's 2018-2019
apparition. At this time Jupiter was
positioned 1° North of the faint gaseous
nebula commonly called
the Lagoon
Nebula (Messier
8
or NGC 6523).
Jupiter
passed through
superior conjunction in late December 2019, re-appearing in the dawn sky in
central Sagittarius
in mid-January 2020, heralding the start of its 2020-2021 apparition. Over the next few weeks Jupiter was positioned several
degrees North of the asterism (star pattern) commonly called the Teapot.
Specifically, the planet was positioned
North of the teapot's handle, which is comprised of four moderately bright stars.
Jupiter continued its Eastward (direct) motion until it reached its Eastern
stationary point in mid-May 2020, a couple of degrees from Sagittarius'
Eastern border. It then turned retrograde and over the next six months described
a zig-zag formation against the faint stars of Eastern Sagittarius.
The planet reached opposition in mid-July 2020, at the centre of the zig-zag,
a few degrees North of the star 52 Sgr (52 Sagittarii, mag.
+4.6). Jupiter then
continued Eastwards and reached its Western stationary point in mid-September
2020. It then resumed direct motion, leaving Sagittarius
and entering Capricornus,
the Sea-Goat in mid-December 2020. The 2020-21 apparition drew to a close as Jupiter headed into the evening
twilight in early January 2021, positioned 5° degrees SSE of the star Dabih (
1
Cap or Beta-1 Capricorni, mag. +3.0v).
Jupiter remained
out of view for the next five weeks, passing through superior conjunction in
late January 2021 before emerging into the dawn sky in mid-February
2021. The 2021-2022 apparition began with Jupiter passing just 2' (2 arcminutes
or 0°.03, where 1 arcminute
= 1/60th of a degree) North of the star
Cap (Theta Capricorni, mag. +4.0) in central Capricornus.
This apparition saw Jupiter ascend
the ecliptic
(the apparent path of the Sun through
the constellations,
which the Moon and planets follow closely)
by a significant amount, improving the planet's visibility for Northern hemisphere
observers and slightly worsening visibility for Southern hemisphere observers
(see the Jupiter Transit
Altitudes section below).
Now heading North-eastwards, Jupiter moved
into Aquarius,
the Water Carrier, in late April 2021, reaching its Eastern stationary point
in the third week of June 2021. The planet then changed direction and headed
South-westwards, retrograding back towards Capricornus
over the next two months and re-entering that constellation in mid-August
2021. Opposition was reached less than a day after crossing the border, with
Jupiter positioned just 7' (0°.11)
West of the boundary with Aquarius.
The planet's 2021-22 'hybrid' loop was described on the border between Capricornus
and Aquarius,
Jupiter
reaching its
Western stationary point in Eastern Capricornus in
mid-October 2021. The planet then resumed direct motion once more, heading North-eastwards
along the ecliptic and re-entering Aquarius
in mid-December 2021. The 2021-22 apparition ended as Jupiter
headed into
the dusk twilight in mid-February 2022, positioned just to the South-west
of the star 
Cap (Lambda Aquarii, mag. +3.9) and 10° SSE
of the so-called Steering
Wheel asterism
which occupies the Northern part of the Water Carrier.
[Terms in yellow italics are explained in greater detail in an associated article describing planetary movements in the night sky.]
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Jupiter in Leo, the Lion photographed by the writer a few days before the planet's opposition in March 2016, when it was positioned near the star Sigma Leonis (at the rear paw of the Lion). Jupiter will return to Leo in 2026 (move your pointer over the image - or click here - for an annotated version and click on the thumbnail for the full-size photo). |
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Jupiter Opposition Data, 2019 to 2021
Data relating to Jupiter's oppositions from 2019 to 2021 are provided in the table below:
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Apparition Period |
Opposition Circumstances |
Superior Conjunction |
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Opposition Date |
Constellation |
Declination |
Apparent Magnitude |
Diameter (arcsecs) |
Tilt |
View from Earth (North up) |
Distance (AU)* |
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Equatorial |
Polar |
from Earth |
from Sun |
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2018/19 |
2019 Jun 10 |
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Oph |
-22°.4 |
-2.5 |
46".0 |
43".1 |
-2°.7 |
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4.2845 |
5.2996 |
2019 Dec 27 |
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2020/21 |
2020 Jul 14 |
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Sgr |
-21°.9 |
-2.6 |
47".6 |
44".6 |
-1°.2 |
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4.1396 |
5.1561 |
2021 Jan 29 |
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2021/22 |
2021 Aug 19 |
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Cap |
-13°.5 |
-2.7 |
49".1 |
46".0 |
+0°.7 |
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4.0134 |
5.0251 |
2022 Mar 5 |
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* 1 AU (Astronomical Unit) = 149,597,870 kms (92,955,807 statute miles) |
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Jupiter opposition data for the period 2019 to 2021. The Declination is the angle of the planet to the North (+) or South (-) of the celestial equator; on the star chart, it represents the planet's angular distance above or below the blue line. The angular diameter (or apparent size) of the planet as seen from Earth is given in arcseconds (where 1 arcsecond = 1/3600th of a degree). Jupiter's opposition distance from Earth slowly reduced throughout the period, so that its angular diameter at opposition increased slightly year by year. This was reflected in the planet's apparent magnitude, which brightened slightly over the period. Jupiter's solar distance also reduced over the period as it headed towards perihelion - its closest orbital point to the Sun - which will take place in January 2023. The Tilt (the inclination of Jupiter's rotational axis relative to the Earth's orbital plane) is positive (+) when Jupiter's Northern hemisphere is tipped towards the Earth and negative (-) when its Southern hemisphere is tipped towards the Earth; the maximum value it can attain is ±3°.4. The Tilt values were obtained from NASA's Jupiter Ephemeris Generator 2.6. All other data was obtained from 'Redshift' and 'SkyGazer Ephemeris' software. The Jupiter images were obtained from NASA's Solar System Simulator. |
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Jupiter Conjunctions with other Planets, January 2019 to March 2021
Six observable conjunctions took place during the period, four of them in the morning sky. Due to Jupiter's high Southerly declination, all of them were more favourably observed from the Southern hemisphere. The planet Saturn, also occupying this region of the zodiac at this time, was positioned not far away from Jupiter in all of these events.
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When Jupiter aligns with Mars a planetary conjunction takes place. This event was photographed by the writer in the dawn sky on January 7th 2018, when both planets were positioned in Libra and separated by just 0°.2 (move your pointer over the image - or click on it - for a closer view). |
Conjunctions between Jupiter and Venus are perhaps the most spectacular of all to view and the most photogenic. Between January 2019 and February 2021 there were three occasions when these two planets could be seen together. The morning conjunction of January 22nd 2019 was visible worldwide and took place only two weeks after Venus' greatest Western elongation from the Sun. Although it had the widest separation of the three conjunctions, it was the only one which could be seen from the whole of the Northern hemisphere and which could also be seen against a dark sky. The Jupiter-Venus conjunction of February 11th 2021 was the closest of the three, the separation between the two planets being 26' (0°.44). It was only visible from Equatorial and Southern hemisphere latitudes. With a solar elongation of just 10° it was a difficult one to observe, the two planets being positioned at most only 6° above the ESE horizon as the fainter planet (Jupiter) disappeared from view in the dawn twilight.
The only evening conjunction between Jupiter and Venus took place on November 24th 2019. With the exception of high-Northern latitudes (where it was not observable), it was a reasonably good conjunction for the Northern hemisphere and was only slightly better for the Southern hemisphere. At latitude 50° North the pair were positioned around 6° high in the South-west as Jupiter came into view in the dusk, whilst at 30° North the pair were around 14° high, also in the South-west. At mid-Southern latitudes the pair stood around 15° to 18° high in the WSW when Jupiter appeared in the twilight. The pair could only be seen against a truly dark sky South of about latitude 45° North.
Conjunctions between Jupiter and Mars provide a good opportunity to compare their differing colours with the naked-eye. The Jupiter-Mars conjunction of March 20th 2020 was a particularly good one for Southern hemisphere observers, the two planets being positioned almost 70° away from the Sun in the constellation of Sagittarius. At magnitude +0.9 Mars was however relatively dim, being several months away from its closest and brightest position in relation to the Earth (at opposition) in October 2020. Together with Saturn to the East, the three planets formed a slender triangle which pointed Eastwards towards Capricornus. At latitude 15° South Jupiter and Mars reached a significant 59° above the ESE horizon as the Red Planet disappeared from view in the twilight. Even at 45° South they were 53° above the ENE horizon when Mars disappeared from view. For Northern hemisphere observers the conjunction was much lower in altitude but nonetheless easily observable. At 30° North the pair reached a respectable 29° above the South-east horizon as Mars faded from view, whilst at 50° North they were 11° high in the South-east.
The rarest of the conjunctions during the period was that between the giant planets Jupiter and Saturn on December 21st 2020. Known historically as Great Conjunctions, Jupiter-Saturn conjunctions take place about every twenty years, the previous one having been in May 2000. However, they are not always best placed for viewing, sometimes taking place at narrow solar elongations. The most spectacular conjunctions between these two planets occur when they are both within days of opposition, at which time they are particularly bright and visible throughout the night. Such events are very rare however, taking place about every 139 years or so (the next will be in the year 2238). Perhaps the best-known conjunction between Jupiter and Saturn was that in the year 7 BC, in the constellation of Pisces, the Fishes. In the early seventeenth century the German astronomer Johannes Kepler (1571-1630) suggested that this event might have been the origin of the Star of Bethlehem, referred to in St Matthew's Gospel of the Bible. Specifically, this was a triple conjunction - a series of three conjunctions which took place between May and December of that year - which, it is argued, was such an unusual chain of events that the Magi (the 'wise men' or astrologers) gave it a special significance. Critics of this theory say, among other things, that the two planets were too far apart to attract any particular attention, their angular separation at best having been about 1° (about two apparent Full Moon diameters).
The 'Great Conjunction' of December 2020 took place on the day of Earth's winter solstice, the planets being only 30° away from the Sun in the evening sky. Whilst not ideally placed for viewing and being well past their opposition dates, Jupiter and Saturn were separated by only 6 arcminutes (0°.1), making them excellent photographic targets through the eyepiece of a telescope. They will next meet in November 2040 in the constellation of Virgo, the Virgin.
Finally, a morning conjunction between Jupiter and Mercury took place on March 5th 2021, only one day ahead of the latter planet's greatest Western elongation. In other words, this was about as far away from the Sun that a planetary conjunction with Mercury could take place. However, the visibility of Mercury is heavily dependant on latitude and local season, and in this case the conjunction could not be viewed from higher-Northern latitudes. Southern Tropical latitudes were best placed to view it, the pair reaching up to 20° in altitude above the Eastern horizon before Mercury disappeared from view in the dawn twilight.
The following table lists the observable conjunctions involving Jupiter which took place during the period in question. In several cases, other planets and/or stars were also in the vicinity and these are detailed. Note that, because some of the conjunctions occurred in twilight, the planets involved may not have appeared as bright as their listed magnitude suggests.
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Jupiter conjunctions with other planets from January 2019 to March 2021 The column headed 'UT' is the Universal Time (equivalent to GMT) of the conjunction (in hrs : mins). The separation (column 'Sep') is the angular distance between the two planets, measured relative to Jupiter, e.g. on 2020 Mar 20, Mars was positioned 0°.7 South of Jupiter at the time shown. The 'Fav. Hem' column shows the Hemisphere in which the conjunction was best observed (Northern, Southern and/or Equatorial). The expression 'Not high N Lats' indicates that observers at latitudes further North than about 45°N will have found the conjunction difficult or impossible to observe because of low altitude and/or bright twilight. In the 'When Visible' column, a distinction is made between Dawn/Morning visibility and Dusk/Evening visibility; the terms Dawn/Dusk refer specifically to the twilight period before sunrise/after sunset, whilst the terms Evening/Morning refer to the period after darkness falls/before twilight begins (some conjunctions take place in darkness, others do not, depending upon latitude). The 'Con' column shows the constellation in which the planets were positioned at the time of the conjunction. To find the direction in which the conjunctions were seen on any of the dates in the table, note down the constellation in which the planets were located ('Con' column) on the required date and find the constellation's rising direction (for Dawn/Morning apparitions) or setting direction (for Dusk/Evening apparitions) for your particular latitude in the Rise-Set direction table. |
There are in fact two methods of defining a planetary conjunction date: one is measured in Right Ascension (i.e. perpendicular to the celestial equator) and the other is measured along the ecliptic which is inclined at 23½° to the Earth's equatorial plane (this is due to the tilt of the Earth's axis in space). An animation showing how conjunction dates are determined by each method can be found on the Jupiter-Uranus 2010-11 triple conjunction page. Although conjunctions measured along the ecliptic can be significantly closer, the Right Ascension method is the more commonly used, and it is the one which is adopted here.
Constellations of the Zodiac: Photographs
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As it slowly moves along the 'celestial highway' known as the ecliptic (the apparent path of the Sun through the constellations, which the Moon and planets follow closely) Jupiter passes numerous bright stars; during the period in question, the bright stars passed by the planet are listed below, in chronological order:
2019
Sco or Epsilon Scorpii, mag. +2.2) in Scorpius,
the Scorpion.
Oph or Eta Ophiuchi, mag. +2.5) in
Ophiuchus,
the Serpent-Bearer (moving direct).
Oph (Theta Ophiuchi, mag. +3.2) in
Ophiuchus,
the Serpent-Bearer (moving direct).
Sco or Lambda Scorpii, mag.
+1.6) in
Scorpius,
the Scorpion (moving direct).
Sco or Lambda Scorpii, mag.
+1.6) in
Scorpius,
the Scorpion (moving retrograde).
Oph (Theta Ophiuchi, mag. +3.2) in
Ophiuchus,
the Serpent-Bearer (moving retrograde).
Oph or Eta Ophiuchi, mag. +2.5)
in Ophiuchus,
the Serpent-Bearer (moving retrograde).
Oph or Eta Ophiuchi, mag. +2.5)
in Ophiuchus,
the Serpent-Bearer (moving direct).
Oph (Theta Ophiuchi, mag. +3.2) in
Ophiuchus,
the Serpent-Bearer (moving direct).
Sco or Lambda Scorpii, mag.
+1.6) in
Scorpius,
the Scorpion (moving direct).
Sco or Theta Scorpii, mag.
+1.9) in
Scorpius,
the Scorpion.2020
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Jupiter reached opposition to the Sun in central Taurus in late 2012. This picture shows the planet in the Western sky before dawn, when it began to sink into the suburban skyglow (move your pointer over the image - or click here - to identify the constellations and click on the thumbnail for the full-size picture). |
Sgr (Phi
Sagittarii, mag.
+3.1) in Sagittarius,
the Archer.
Sgr or Sigma Sagittarii, mag. +2.0) in Sagittarius,
the Archer.
Sgr
(Xi Sagittarii, mag.
+3.5) in Sagittarius,
the Archer.
Sgr or Zeta Sagittarii, mag. +2.6) in Sagittarius,
the Archer.
Sgr (Omicron Sagittarii, mag. +3.7) in Sagittarius,
the Archer.
Sgr
(Tau Sagittarii, mag.
+3.3) in Sagittarius,
the Archer.
Sgr or Pi Sagittarii, mag. +2.9) in Sagittarius,
the Archer.
Sgr (Rho Sagittarii, mag. +3.9) in Sagittarius,
the Archer (moving direct).1
Sgr or Beta-1 Sagittarii, mag.
+3.9) in Sagittarius,
the Archer (moving direct).2
Sgr or Beta-2 Sagittarii, mag.
+4.2) in Sagittarius,
the Archer (moving direct).
Sgr
or Alpha Sagittarii, mag.
+3.9) in Sagittarius,
the Archer (moving direct).
Sgr or Omega Sagittarii, mag. +4.7) in Sagittarius,
the Archer (moving direct).
Sgr or Omega Sagittarii, mag. +4.7) in Sagittarius,
the Archer (moving retrograde).
Sgr
or Alpha Sagittarii, mag.
+3.9) in Sagittarius,
the Archer (moving retrograde).2
Sgr or Beta-2 Sagittarii, mag.
+4.2) in Sagittarius,
the Archer (moving retrograde).1
Sgr or Beta-1 Sagittarii, mag.
+3.9) in Sagittarius,
the Archer (moving retrograde).
Sgr (Rho Sagittarii, mag. +3.9) in Sagittarius,
the Archer (moving retrograde).
Sgr (Rho Sagittarii, mag. +3.9) in Sagittarius,
the Archer (moving direct).1
Sgr or Beta-1 Sagittarii, mag.
+3.9) in Sagittarius,
the Archer (moving direct).2
Sgr or Beta-2 Sagittarii, mag.
+4.2) in Sagittarius,
the Archer (moving direct).
Sgr
or Alpha Sagittarii, mag.
+3.9) in Sagittarius,
the Archer (moving direct).
Sgr or Omega Sagittarii, mag. +4.7) in Sagittarius,
the Archer (moving direct).1
Cap or
Alpha-1 Capricorni, mag. +4.2) in Capricornus,
the Sea-Goat.2
Cap or
Alpha-2 Capricorni, mag. +3.6) in Capricornus,
the Sea-Goat.2021
1
Cap or Beta-1 Capricorni, mag. +3.0v) in Capricornus,
the Sea-Goat.
Cap (Theta Capricorni, mag. +4.0) in Capricornus,
the Sea-Goat.
Cap (Iota Capricorni, mag. +4.3) in Capricornus,
the Sea-Goat.
Cap (Zeta Capricorni, mag. +3.8) in Capricornus,
the Sea-Goat.
Aqr or Beta Aquarii, mag. +2.9) in Aquarius,
the Water Carrier.
Cap or Gamma Capricorni, mag. +3.7) in Capricornus,
the Sea-Goat.
Cap or Delta Capricorni, mag. +2.9v) in Capricornus,
the Sea-Goat (moving direct).
Aqr or Alpha Aquarii, mag. +2.9) in Aquarius,
the Water Carrier (moving direct).
Aqr (Iota Aquarii, mag. +4.2) in Aquarius,
the Water Carrier (moving direct).
Aqr or Theta Aquarii, mag. +4.1) in Aquarius,
the Water Carrier (moving direct).
Aqr or Theta Aquarii, mag. +4.1) in Aquarius,
the Water Carrier (moving retrograde).
Aqr (Iota Aquarii, mag. +4.2) in Aquarius,
the Water Carrier (moving retrograde).
Aqr or Alpha Aquarii, mag. +2.9) in Aquarius,
the Water Carrier (moving retrograde).
Cap or Delta Capricorni, mag. +2.9v) in Capricornus,
the Sea-Goat (moving retrograde).
Cap or Gamma Capricorni, mag. +3.7) in Capricornus,
the Sea-Goat (moving retrograde).
Cap or Gamma Capricorni, mag. +3.7) in Capricornus,
the Sea-Goat (moving direct).
Cap or Delta Capricorni, mag. +2.9v) in Capricornus,
the Sea-Goat (moving direct).
Aqr or Alpha Aquarii, mag. +2.9) in
Aquarius,
the Water Carrier (moving direct).
Aqr (Iota Aquarii, mag. +4.2) in Aquarius,
the Water Carrier (moving direct).2022
Aqr or Theta Aquarii, mag. +4.1) in Aquarius,
the Water Carrier (moving direct).
Aqr or Gamma Aquarii, mag. +3.8) in Aquarius,
the Water Carrier.
Aqr (Zeta Aquarii, mag. +4.3) in Aquarius,
the Water Carrier.
Aqr (Eta Aquarii, mag. +4.0) in Aquarius,
the Water Carrier.
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Jupiter Transit Altitudes, 2019 to 2021
After 2015 viewing circumstances for Southern hemisphere observers improved year-on-year as Jupiter headed towards its most Southerly declination in Sagittarius in December 2019. Conversely, the viewing circumstances for Northern hemisphere observers worsened over this period, giving less-than-optimal viewing conditions for telescopic observers. Jupiter began to ascend the ecliptic once more after the 2020-21 apparition.
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Transit altitudes of Jupiter at successive oppositions from 2019 to 2021, as seen from a variety of latitudes. The Declination (Dec.) is the angle of the planet to the North (+) or South (-) of the celestial equator at the time of the planet's opposition. The Altitude Range is the approximate altitude variation over the course of the apparition, e.g. for the 2018/19 apparition at latitude 40° North, the transit altitude of Jupiter ranged from (27°.6 - 1°.1) = 26°.5 to (27°.6 + 1°.1) = 28°.7. The table shows that, after 2020, Jovian transit altitudes improved significantly for Northern hemisphere observers but worsened for Southern hemisphere observers. |
Moon near Jupiter Dates, 2021
The Moon is easy to find, and on one or two days in each month, it passes Jupiter in the sky. Use the following table to see on which dates the Moon was in the vicinity of the planet during 2021:
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Moon near Jupiter dates for 2021. The Date Range shows the range of dates worldwide (allowing for Time Zone differences across East and West hemispheres). Note that the dates, times and separations at conjunction (i.e. when the two bodies were at the same Right Ascension) are measured from the Earth's centre (geocentric) and not from the Earth's surface (times are Universal Time [UT], equivalent to GMT). The Sep. & Dir. column gives the angular distance (separation) and direction of the planet relative to the Moon, e.g. on April 7th at 07:17 UT, Jupiter was 4°.4 North of the Moon's centre. The Moon Phase shows whether the Moon was waxing (between New Moon and Full Moon), waning (between Full Moon and New Moon), at crescent phase (less than half of the lunar disk illuminated) or gibbous phase (more than half but less than fully illuminated). Moon near Jupiter dates can also be viewed for 2018, 2019 and 2020. |
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The Moon moves relatively quickly against the background stars in an Eastward direction, at about its own angular width (0º.5) each hour (about 12º.2 per day). Because it is relatively close to the Earth, an effect called parallax causes it to appear in a slightly different position (against the background stars) when seen from any two locations on the globe at any given instant; the further apart the locations, the greater the Moon's apparent displacement against the background stars. Therefore, for any given date and time listed in the table, the Moon will have appeared closer to Jupiter when seen from some locations than from others. For this reason, the dates shown in the table should be used only for general guidance.
Jupiter's Four Brightest Moons, 2019 to 2021
Jupiter's four brightest moons (satellites) - namely Ganymede (magnitude +4.6 at opposition), Io (+5.0), Europa (+5.3) and Callisto (+5.6) - can readily be seen through telescopes or steadily-held binoculars. The moons are seen to change their position in relation to each other, along the planet's equatorial plane, from one night to the next. In fact, their motion can be detected in the space of just a few hours.
Due to Jupiter's shallow axial tilt (3º.1 to the plane of its orbit), the Jovian moons appear to present a more-or-less linear motion when seen from the Earth. This is in contrast to, say, Saturn with its relatively high axial tilt (26º.7), which causes its moons to mostly follow apparent elliptical paths around the planet when viewed from the Earth (see Saturn's moon positions). Approximately every six years, when the Earth passes through Jupiter's equatorial plane, the Jovian moons are seen to become involved in mutual occultations (where the moons pass in front of each other) and mutual eclipses (where a moon's shadow falls upon another moon). Numerous mutual events took place during the 2014-15 observing period and between January 2021 and March 2022.
According to Italian amateur astronomer Pierpaulo Ricci, there are 25 occasions during the 21st century when Jupiter appears without any of its four brightest moons. On these occasions the moons are either passing in front of the Jovian disk (in transit), passing behind it (in occultation) or positioned within the planet's shadow (in eclipse). During the period in question Jupiter appeared without any of these moons on the following dates and times: November 9th 2019 (from 1216 UT to 1253 UT), May 28th 2020 (from 1115 UT to 1311 UT) and August 15th 2021 (from 1539 UT to 1545 UT). The next such event will take place in July 2033.
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.Copyright Martin J Powell 2018-2021
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