The Venus Morning Apparition

of 2017

by Martin J. Powell

The path of Venus through the zodiac constellations during the planet's morning apparition in 2017 (click on thumbnail for the full-size image, 45 KB). A version with constellation labels can be seen here (60 KB). Constellation names are shown in their three-letter abbreviated format - the full names are listed here. Zodiac constellations are labelled in green and non-zodiac constellations in grey. The numbers along the sides of the chart (Right Ascension and Declination) are co-ordinates of celestial longitude and latitude which are used to locate the position of celestial bodies in the night sky. A print-friendly version is available here (21 KB).

Venus passed through inferior conjunction (when it was positioned between the Earth and the Sun) on March 25th 2017, positioned a siignificant 8º.3 North of the Sun's centre. For observers at latitudes North of about 50º North, Venus was positioned sufficiently far North of the Sun - and thus sufficiently far above the Eastern horizon - for it to be glimpsed in the bright dawn twilight from inferior conjunction day itself. Elsewhere the planet swiftly entered the dawn sky as a 'Morning Star' over the following week, visible in the twilight, low down over the Eastern horizon less than 30 minutes before sunrise (the exact period depending upon the observer's latitude).

Orbitally, Venus was positioned at a relatively close 0.281 Astronomical Units (AU) from the Earth (42 million kms or 26.1 million statute miles), a distance which would continually increase over the next nine months, through to the end of the apparition. The planet was moving retrograde (East to West) at this time, positioned in the central Western region of the constellation of Pisces, the Fishes. Venus reached a solar elongation of 10º West on March 29th, and on the same day the planet briefly left Pisces and entered the adjacent constellation of Pegasus, the Flying Horse. Venus clipped the constellation's South-eastern corner, moving diagonally across it, before returning to Pisces just two hours later. The planet shone at an apparent magnitude of -4.1 and its apparent diameter (its angular width as seen from the Earth) was a sizeable 59" (i.e. 59 arcseconds, where 1 arcsecond = 1/3600th of a degree). Venus' apparent diameter would continually shrink during the apparition, as it slowly receded from the Earth in space.

On April 3rd the apparition truly got underway as Venus reached an elongation of 15º West, making it more readily visible in the dawn twilight from all except higher Northern latitudes. By April 7th the planet was moving into the Circlet of Pisces, a group of faint stars which form the head of the Southernmost fish. On April 13th, whilst within the Circlet, Venus reached its Western stationary point, some 1º.5 West of the variable star 19 Piscium or TX Piscium (mag. +5.0v). Now moving Southward, the planet passed 0º.5 North of Psc (Lambda Piscium, mag. +4.5), located at the South-eastern corner of the Circlet, on April 17th. Venus left the Circlet on the following day, arcing its way around towards the South-east against the background stars.

Venus as a thin crescent photographed through a 9¼" SCT telescope in the dawn twilight by Vincenzo Mirabella (Ardea, Italy) in August 2015. The planet was 7% illuminated and positioned 22° West of the Sun (click on the thumbnail for the full-size picture, 16 KB). (Image: Vincenzo Mirabella/ALPO-Japan)

As it pulled away from the Sun, telescopes pointed towards Venus showed a large, slender, Eastward-facing crescent, rippling in the Earth's turbulent atmosphere (click here to see how Venus typically appears through a small telescope at various phases). The planet's phase (i.e. the percentage of the disk which is illuminated) was only around 5% (phase = 0.05). The planet's large apparent diameter also meant that the crescent could be glimpsed in the twilight by observers using binoculars, its apparently tiny crescent facing down towards the horizon.

At this early stage of the apparition, dedicated telescopic observers of Venus now began their search for the elusive Ashen Light, which is a faint glowing of the night side of Venus through its thick clouds. The phenomenon is believed to be caused either by the planet's surface glowing red hot (due to its extremely high surface temperature) or due to electrical activity in its dense atmosphere. Observers searching for the Light will normally use ultraviolet and/or infrared filters in order to help reveal it, an occulting bar often being used to block the bright, visually-intrusive crescent from view. Observers in higher Southern latitudes were best placed to view the Light at this stage of the apparition due to the planet's higher altitude (angle above the horizon) before sunrise.

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Observers at higher Northern latitudes had considerable difficulty viewing Venus at this early stage of the apparition, the planet rising in twilight and barely reaching a few degrees above the horizon before the sky became too bright to see it with ease. At latitude 60º North the planet's visibility worsened slightly over the next month because its position along the ecliptic (the path of the Sun, which the Moon and planets follow very closely) placed it very low down above the Eastern horizon at dawn at this time of year. From these latitudes Venus would not become visible with greater ease until about mid July. Elsewhere the planet was rising 1¼ hours before sunrise (at 50º North), 1¾ hours before sunrise (at 30º North), 2 hours before sunrise (at the Equator) and 2½ hours before the Sun (at 35º South). At thirty minutes before sunrise, Venus stood just 7º high in the East at 50º North, 15º high in the East at 30º North, 23º high in the East at the Equator and 24º high in the ENE at 35º South.

On April 26th Venus attained its greatest brilliancy for this apparition, at magnitude -4.5. This is the position in the planet's orbit when its phase, its apparent size and its apparent magnitude combine to best visual effect, as seen from the Earth. At greatest brilliancy in the current apparition, Venus was positioned 37° West of the Sun with a 23% illuminated crescent (phase = 0.23) and an apparent diameter of 41".2. Southern hemisphere observers had the best view of the planet as it blazed brilliant white against a truly dark sky.

In late April Venus was joined in the dawn sky by the planet Mercury (mag. +3.0), now commencing its second morning apparition of 2017. Owing to the steep angle of the ecliptic to the local Eastern horizon at dawn at this time of year, this apparition of Mercury favoured observers in the Southern hemisphere. It was one of two paired apparitions between Venus and Mercury which took place during the year (a paired apparition being when the two planets are visible together for a prolonged period of time, either in the morning sky or the evening sky). This particular pairing lasted through to early June; it was an interesting one because both planets reached their greatest elongations from the Sun during the period.

Venus crossed the ecliptic in a Southward direction on May 9th and on May 11th it again exited the zodiac for a short period of time. The planet entered the constellation of Cetus, the Whale, at around 0200 UT, cutting across its North-western corner, returning to Pisces at around 1700 UT on the same day. This was the first of two excursions into the Whale constellation which the planet would make over the course of the next 30 days.

Venus and Mercury came to within 19º of each other around the 15th of the month, Mercury attaining its greatest elongation from the Sun (26º West) two days later, shining at an apparent magnitude of +0.6. The waning crescent Moon passed near the two planets between May 21st and 24th, providing an ideal photographic opportunity to capture our sole natural satellite and the two innermost planets of the Solar System together in the morning sky. On May 18th Venus passed 3º.5 South of the star Delta Piscium ( Psc, mag. +4.4), positioned about half-way along the Southern Fish's body, and then 2º.8 South of the star Epsilon Piscium ( Psc, mag. +4.3) on May 22nd.

From mid to late May, observers at mid-Southern latitudes saw Venus attain its highest altitude in the sky before sunrise for the 2017 apparition. At 35° South, the planet rose 3¾ hours before the Sun, reaching an altitude of around 35° in the North-east at 30 minutes before sunrise. Elsewhere, Venus rose in the East 1½ hours before sunrise (at 50° North), 2¼ hours before sunrise (at 30° North) and almost three hours before sunrise (at the Equator). For Southern hemisphere observers this was the second best of Venus' five morning apparitions during its 8-year cycle, the planet typically attaining higher-than-average altitudes above the horizon when compared to the other four morning apparitions (for more details, see the accompanying article describing The Venus 8-year Cycle).

On June 2nd Venus, having faded slightly to mag. -4.2, passed 1°.8 South of the planet Uranus (mag. +5.9) in the first of three planetary conjunctions which took place during the 2017 morning apparition. A planetary conjunction (or appulse) takes place whenever two planets attain the same celestial longitude in the night sky (i.e. they appear to 'line up' when seen from the Earth). This first conjunction was best seen from the Southern hemisphere; details of this and the other planetary conjunctions involving Venus during the year are given in the 'planetary conjunctions' section below.

For Equatorial observers, early June saw the planet attain its highest altitude above the horizon before sunrise for the current apparition. Here Venus rose three hours before the Sun, reaching a significant 37° above the ENE horizon some 30 minutes ahead of sunrise. In fact, when assessed in terms of the planet's horizon altitude and visibility duration before sunrise, the 2017 morning apparition of Venus was best seen overall from Equatorial latitudes.

Around 1200 UT on June 3rd, Venus reached its greatest Western elongation (45°.86 West of the Sun), positioned 1°.7 to the SSW of Uranus and 0°.9 SSW of the star Torcularis Septentrionalis ( Psc or Omicron Piscium, mag. +4.2) in the tail of the Northern Fish. Although the planet's greatest elongation from the Sun took place on June 3rd, Venus was in fact positioned at an elongation of 45°.8 for a 12-day period from May 29th through to June 9th.

Crescent Venus at 41% phase photographed through a 250mm Newtonian telescope by Stephane Gonzales (Surgeres, France) in October 2015. The photo hints at the pale 'lemon yellow' colouration which is often reported by dedicated telescopic observers of the planet (click on the thumbnail for the full-size picture, 15 KB) (Image: Stephane Gonzales)

Contrary to what one might think, greatest elongation day is not necessarily the day on which Venus is above the horizon ahead of sunrise for the longest period of time. Since the angle of the ecliptic to the Eastern horizon at dawn varies with the observer's latitude, Venus was above the horizon for differing periods of time. At 60° North Venus rose just 50 minutes before sunrise, whilst at 50° North the planet rose 1¾ hours before the Sun. At other latitudes the visibility durations were as follows: two hours at 40° North; 2½ hours at 30° North; 2¾ hours at 20° North; three hours at the Equator; 3¼ hours at 15° South; 3½ hours at 25° South; 3¾ hours at 35° South and four hours at 45° South. Hence for the current apparition, observers at higher Southern latitudes were best placed to see Venus above the horizon for the longest period on greatest elongation day.

Telescopes now showed Venus' disk half-illuminated (phase = 0.50) with an apparent diameter of 23".8. Theoretically, greatest elongation is the time at which the planet's terminator (the line separating the light and dark sides of the planet) appears perfectly straight through telescopes, essentially dividing Venus into two perfect halves; this is known as the dichotomy. However, telescopic observers often report the straight terminator several days earlier or later than the greatest elongation date. Interestingly, the date of dichotomy is usually reported early in evening apparitions and late in morning apparitions. The precise reason for this phenomenon - which is referred to as Schröter's Effect - is not known, however it may simply be due to the fact that the precise moment of dichotomy cannot be determined by an observer to within an accuracy any better than a few days.

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Some eleven hours after reaching greatest elongation, Venus passed 1º.8 North of Torcularis Septentrionalis (Latin for 'North Press', a mistranslation of an original Greek word meaning 'flax', i.e. the cord that ties the two fishes' tails together). The planet will occult (pass in front of) this star during its 2027 morning apparition.

Venus entered Cetus once more at around 1415 UT on June 9th, passing 13°.2 South of the star Hamal ( Ari or Alpha Arietis, mag. +2.0) in neighbouring Aries, the Ram before entering Aries itself the following day at around 1905 UT. The planet passed 4º.6 South of Botein ( Ari or Delta Arietis, mag. +4.3), the Ram's Easternmost bright star, on June 25th.

Greatest elongation day long having passed, telescopes showed Venus with a 60% illuminated phase (slightly gibbous) in late June. The planet's phase would remain gibbous through the remainder of the apparition. The apparent diameter had reduced slightly to around 19" and the planet shone at an apparent visual magnitude of -4.1.

Venus entered Taurus, the Bull, on June 28th, passing 3º.3 North of the star 5 Tau (5 Tauri, mag. +4.1) on June 30th. The planet would spend most of July in this constellation, the most Northerly of the zodiac.

At around 0800 UT on July 3rd Venus began to pass South of Taurus' most famous star cluster called the Pleiades (pronounced 'PLY-add-eez' or 'PLEE-add-eez'), also known as the Seven Sisters (Messier 45). The planet took about 22 hours to traverse the 1° angular distance between the cluster's brightest Western star (Electra, mag. +3.7) and its brightest Eastern star (Atlas, mag. +3.6). The vertical angular distance between the cluster and the planet was about 7°. On July 6th the planet passed 5°.5 North of the eclipsing binary star Tau (Lambda Tauri), whose magnitude varies from ca. 3.5 to 4.0 over a period of four days.

Since inferior conjunction in late March, Venus had been receding from the Earth in space at an average rate of about 996,000 kms (619,000 miles) per day. At 1502 UT on July 11th, Venus was positioned at precisely 1.000 AU from the Earth, i.e. the same distance as the average distance of the Earth from the Sun (149.5 million kms or 92.9 million statute miles).

Between July 11th and 14th Venus passed a few degrees North of another, much larger star cluster known as the Hyades, a distinct 'V'-shaped grouping of stars forming the head of the Bull. At the apex of the 'V' is a star known variously as Prima Hyadum, Primus Hyadum or Hyadum I ( Tau or Gamma Tauri, mag. +3.6). Venus passed 3°.3 North of the star at around midnight UT on July 11th. Sixteen hours later the planet passed 1°.6 North of Hyadum II (¹ Tau or Delta-1 Tauri, mag. +3.7), a triple star system positioned about half-way along the Northern arm of the 'V'. Also positioned along the Northern arm is the star Ain ( Tauri, mag. +3.5), marking the base of the Bull's Northern horn. Venus passed just 11' (11 arcminutes, where 1 arcminute = 1/60th of a degree) North of the star at around 2130 UT on July 12th. Occupying the South-eastern corner of the Hyades cluster is the orange-red star Aldebaran ( Tau or Alpha Tauri, mag. +0.9), marking the 'eye' of the Bull. Its coloration derives from the fact that it is a red giant star. Most of the Hyades stars comprise a genuine cluster, moving through space together, however Aldebaran is not part of the group; it is a foreground star, positioned closer to the Earth than the cluster. Venus passed 3°.2 North of Aldebaran on July 14th.

Venus pictured in the dawn sky during the planet's 2012-13 morning apparition (click on the thumbnail for the full-size picture, 148 KB).

Around mid July, observers situated at Northern Tropical latitudes saw the planet attain its highest altitude before sunrise for the 2017 morning apparition. At 30° North, Venus rose almost three hours ahead of the Sun, reaching 29° above the Eastern horizon at half-an-hour before sunrise. Elsewhere the planet was also rising about three hours before the Sun; at 30 minutes before sunrise, Venus reached 14° high in the ENE at 60° North, 20° high in the East at 50° North, 32° high in the ENE at the Equator and 23° high in the North-east at 35° South.

About half-way along the Bull's Southern horn is the unremarkable fifth-magnitude star 104 Tauri (mag. +4.9). At around 1115 UT on July 20th, observers in Southern Argentina and Southern Chile were able to observe the waning crescent Moon pass in front of this star, obscuring it from view, in an event called a lunar occultation. Elsewhere the Moon was seen in the vicinity of the star from around 10 to 14 hours UT on the same day. Venus itself passed 2°.2 North of the star on the following day (July 21st); it too will occult the star during the course of its morning apparition in July 2028.

On July 25th Venus passed 7°.2 South of the star Al Nath or El Nath ( Tau or Beta Tauri, mag. +1.6), located at the tip of the Bull's Northern horn. The star also has the name Gamma Aurigae ( Aur) since, apart from marking one of the Bull's horns, it also neatly completes the six-sided figure comprising the stars of Auriga, the Charioteer, located to the North-east of Taurus. The star marking the tip of the Bull's Southern horn is Zeta Tauri ( Tau, mag. +2.9v) and Venus passed just 23' (0°.4) North of it on July 27th.

Venus left Taurus and again departed the zodiac for a short while, entering the constellation of Orion, the Hunter, on July 29th. The planet then cut across the North-eastern section of the constellation, just above the Hunter's club, passing 1°.5 North of the star Chi Orionis (¹ Ori, mag. +4.4) on July 30th. Venus left Orion and crossed into Gemini, the Twins, on July 31st.

August commenced with Venus passing 1°.3 South of the star 1 Gem (1 Geminorum, mag. +4.2), the Westernmost bright star in Gemini, marking the foot of the Northern twin. On August 3rd the planet passed 0°.5 South of the star Propus or Tejat Prior ( Gem or Eta Geminorum, mag. +3.5v) and on August 5th, 0°.5 South of the star Tejat Posterior ( Gem or Mu Geminorum, mag. +3.0v), which marks the Northern twin's knee.

At around 20 hours UT on August 5th, Venus attained its most Northerly declination (symbol ) for this apparition, at = +21° 58' 16" (or +21°.97 in decimal format). Across the world, the planet now rose at its most Northerly point along the local horizon, the actual point of rising depending upon the observer's latitude. In early August at higher Northern latitudes Venus rose in the North-east, whilst at latitudes further South it rose in the ENE. The planet was now 1°.3 South of the ecliptic, so it was by no means as far North as the planet is capable of travelling. Indeed, the next highest declination which Venus will attain will be +27°.81 during its evening apparition in May 2020, when it will be positioned in North-eastern Taurus, close to the border with Auriga. This will be the highest declination attained by planet until the year 2077.

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Around early to mid August, observers at high and mid-Northern latitudes saw Venus attain its highest altitude in the sky before sunrise for the 2017 apparition. From higher Northern latitudes, the planet was now rising in darkness, having spent the previous two months of the apparition rising in twilight. At latitude 60° North, the planet rose over 3½ hours ahead of the Sun, attaining an altitude of 19° above the Eastern horizon at 30 minutes before sunrise. At mid-Northern latitudes, the planet rose a little over three hours before the Sun, reaching 22° above the Eastern horizon at 30 minutes before sunrise. These altitudes were not particularly high; for naked-eye observers in the Northern hemisphere, the 2017 apparition was only the third best of Venus' five morning apparitions over the planet's 8-year cycle (see the accompanying article describing The Venus 8-year Cycle). From Northern latitudes this apparition saw Venus attain only moderate altitudes above the horizon at dawn when compared to the other four morning apparitions.

On August 6th Venus passed 1°.7 North of the star  Gem (Nu Geminorum, mag. +4.1), the lower foot of the Northern twin, which the planet will occult in August of 2028. On August 8th the planet passed 5°.5 North of Alhena ( Gem or Gamma Geminorum, mag. +1.9) at the foot of the Southern twin, then on the 9th, 3°.2 South of Mebsuta ( Gem or Epsilon Geminorum, mag. +3.0) positioned at the groin of the Northern twin. Venus now appeared at the apex of an isoscelene triangle with Gemini's brightest stars Castor ( Gem or Alpha Geminorum, mag. +1.6) and Pollux ( Gem or Beta Geminorum, mag. +1.1), the long sides of the triangle measuring a little over 15° and the angular distance of the short side (from Castor to Pollux) being 4°.5. The temporary celestial triangle pointed South-westwards towards Orion.

On August 13th Venus passed 1°.1 North of the optical double star Mekbuda (Gem or Zeta Geminorum, mag. +3.9v), positioned at the right knee of the Southern twin, then passed 0°.5 North of the star Wasat ( Gem or Delta Geminorum, mag. +3.5) on August 16th. Venus passed 10°.7 South of Castor itself on August 19th.

At around 1045 UT on August 21st, Pollux, Gem (Kappa Geminorum, mag. +3.5) and Venus (mag. -4.0) formed a straight line about 7°.2 in length, aligned roughly North-South. The angular distances between Pollux and   Gem and between Gem and Venus were about the same (ca. 3°.5). As luck would have it, the line pointed almost directly towards the bright star Procyon ( CMi or Alpha Canis Minoris, mag. +0.5) in the constellation of Canis Minor, the Lesser Dog, some 15°.7 to the South of Venus.

As millions looked skyward to observe the total solar eclipse over the USA later that same day, Venus was positioned 34°.3 West of the Sun; at minus fourth magnitude the planet was easily seen against the twilit sky, caused by the eclipse totality (the positions of the planets in relation to the eclipsed Sun are discussed here). At around 1845 UT, shortly before the Moon's shadow left the coast of South Carolina and headed out into the Atlantic Ocean, Venus passed 7°.2 South of Gemini's brightest star Pollux.

On August 24th, the planet left Gemini and entered the constellation of Cancer, the Crab, passing 10°.4 North of the star Altarf ( Cnc or Beta Cancri, mag. +3.5) three days later. Venus crossed the ecliptic heading Northwards on August 30th.

At the start of September Venus was positioned around 1° South of the star cluster known as Praesepe (pronounced 'PRE-SEEP-EE'), designated M44 or NGC 2632. It is also known by the names Beehive Cluster (the reason being evident when one looks at the cluster through binoculars) or, more rarely, The Manger. Venus took some 17 hours to traverse the angular width of the cluster, commencing its passage at around 1030 UT on September 1st and completing it at around 0330 UT on September 2nd. The planet passed just 5' (0°.08) North of the star Asellus Australis ( Cnc or Delta Cancri, mag. +3.9), positioned to the South-east of the cluster, later that same day.

In early September Venus was rising 3½ hours before the Sun at latitude 60° North, reaching an altitude of 18° in the East at 30 minutes before sunrise. At 50° North the planet rose three hours ahead of the Sun, reaching 21° high in the East at 30 minutes before sunrise. At latitudes further South the durations, altitudes and directions at a half-hour before sunrise were as follows: 2½ hours before sunrise, reaching 23° in the East (at 30° North); two hours before sunrise, reaching 20° in the ENE (at the Equator) and 1½ hours before sunrise, reaching 10° in the ENE (at 35° South).

On September 5th Venus passed 5°.6 North of the star Acubens ( Cnc or Alpha Cancri, mag. +4.2), which is positioned at the South-eastern corner of the Crab constellation's lambda-shaped () pattern. Around this time, Venus was again joined in the dawn sky by the planet Mercury (mag. +1.3) in the second of two paired apparitions between the two planets during 2017. Unlike Mercury's previous morning apparition in April, this one favoured Northern hemisphere observers. Venus entered Leo, the Lion, on September 10th, Mercury reaching greatest elongation two days later, at 18° West of the Sun. The two planets did not get close enough to reach conjunction, Mercury at best coming to within 11° of Venus on September 14th.

A Gibbous Venus sketched in June 2014 by David Gray (Kirk Merrington, UK) using a Dall-Kirkham 415mm telescope at 365x magnification. The subtle cloud features were revealed using deep yellow, blue and green-tricolor filters (click on the thumbnail for the full-size image, 4 KB) (Image: David Gray/ALPO-Japan)

Also on September 14th, Venus passed 4°.7 North of the star Subra ( Leo or Omicron Leonis, mag. +3.5), marking the paw of the Lion's foreleg. Between September 15th and 22nd Venus was positioned South of the asterism known as the Sickle of Leo, at the Western end of the constellation, which appears to the naked-eye as a backward question-mark (). The constellation's brightest star Regulus ( Leo or Alpha Leonis, mag. +1.4) is in the equivalent position of the dot.

Some 13° to the East of Venus, Mars (mag. +1.8) was now emerging out of the dawn twilight into the start of its 2017-19 apparition. On September 16th Mars and Mercury were in close conjunction with each other, just 0°.1 apart, the pair being positioned 11°.2 to the ESE of Venus. The conjunction was a difficult one to observe, however, taking place just 17° from the Sun and visible only from the Northern hemisphere. The waning crescent Moon passed near the three planets between September 17th and 19th.

Between September 18th and 19th the Moon passed to the South of Venus, forming a triangular arrangement with nearby Regulus as seen from locations North of the Equator. At around 0055 UT on September 18th, observers in the Eastern Indian Ocean were able to see the Moon pass in front of Venus, obscuring it from view, in a lunar occultation. Here the event was seen in darkness and/or twilight, depending upon the precise location of the observer. In Australia, New Zealand, Indonesia and Papua New Guinea observers saw the event in daylight. Further details of this event can be found by following the link in the 'Moon near Venus Dates' section below.

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At 1730 UT on the same day (September 19th local time), Mars was seen to be occulted by the Moon in twilit conditions by observers located within a narrow strip of the North-western Pacific Ocean. Venus was 10° to the WNW of the Red Planet at this time. The re-appearance of Mars was visible just after Moonrise at around 1830 UT from the remote island of Minami-Tori-shima (Marcus Island).

A third lunar occultation took place on this day: at around 2050 UT Mercury, now at magnitude -0.9 and just 16° West of the Sun, was also occulted by the thin waning crescent Moon. The event was seen in twilight just after Moonrise from South-eastern China, Taiwan and the Philippines.

Between the two latter events, the Moon, Mercury and Mars formed a tight trio less than 2° apart, the closest grouping between these three celestial bodies before the year 2036. Venus was positioned about 11° to the WNW of the trio. From the Northern Mariana Islands, the Moon was seen nicely positioned midway between Mercury and Mars in the brightening twilight shortly after Moonrise on September 19th local time.

Mercury and Venus continued to be visible together as 'morning stars' through to about the 20th of the month, after which Mercury headed out of view into the twilight.

Venus passed 0°.5 North of Regulus on September 19th, a relatively close pass which was visible shortly before dawn twilight from Eastern India, Northern Pakistan, Western China and Western central Russia. Venus will occult Regulus during its morning apparition in 2044, the brightest star to be occulted by the planet up until that year; the occultation will be visible at dawn from Eastern Asia.

By late September Venus' solar elongation had reduced to 25° and it appeared only slightly gibbous through telescopes, showing a 90% illuminated phase. The apparent disk diameter was around 11", i.e. only half the size it had been in mid June and a third of the size it had been in mid May. With such a small disk size, little could now be discerned in the way of the planet's characteristic cloud markings.

Mid-Southern hemisphere observers now had a rapidly shortening window in which to observe Venus. At latitude 35° South, the planet rose in twilight only an hour ahead of the Sun, attaining just 5° in altitude in the ENE at 30 minutes before sunrise.

Since the first appearance of Mars in the dawn sky in mid-September, Venus had been closing in on the Red Planet at an average rate of 0°.6 per day. On October 5th the two planets met, Venus passing just 0°.2 North of Mars in a planetary conjunction which was best seen from the Northern hemisphere. The star Leo (Sigma Leonis, mag. +4.0), at the foot of the Lion's hind leg, was positioned just 0°.3 to the NNE of Venus at the time of the conjunction. One hour after the event, Venus passed 0°.3 South of the star. Further details of the event can be seen in the 'planetary conjunctions' section below.

Venus entered Virgo, the Virgin, on October 9th, a constellation which Southern hemisphere observers were already having some difficulty viewing in the dawn twilight. The planet passed 3°.3 South of the star  Vir (Nu Virginis, mag. +4.0), at the top of the Maiden's head, on October 11th, then 0°.8 North of Zavijah ( Vir or Beta Virginis, mag. +3.6), at the back of her head, on October 12th.

From mid October, observers situated at mid-Southern latitudes were the first to lose sight of Venus from the dawn sky as it slipped into the bright Eastern horizon.

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Venus crossed the celestial equator (where the declination of a celestial body is 0°) heading Southwards on October 17th, causing the planet to rise due East across the inhabited world. On October 18th Venus passed 0°.2 North of the star Zaniah ( Vir or Eta Virginis, mag. +3.8) then five days later (23rd) 1°.3 South of the double star Porrima or Arich ( Vir or Gamma Virginis, mag. +3.5). The planet passed 0°.2 South of another double star, Theta Virginis ( Vir, mag. +4.4) on October 29th.

In late October Venus was rising two hours before sunrise at 60º North, 1¾ hours before sunrise at 50º North, 1¼ hours before the Sun at 30º North and one hour before the Sun at the Equator. At thirty minutes before sunrise, Venus attained an altitude of 9º in the ESE at 60º North, 10º in the ESE at 50º North, 10º high in the East at 30º North and just 7º high in the East at the Equator. Telescopes turned towards Venus now showed a tiny disk measuring a little over 10" across and showing a phase of around 95% - so slightly gibbous that the planet effectively appeared 'full'.

On November 1st Venus passed 3º.8 North of Virgo's brightest star, Spica ( Vir or Alpha Virginis, mag. +1.0), a blue-white star which dominates the South-eastern region of the constellation.

By November 6th Venus' solar elongation had reduced to just 15º and from the latitudes which were still able to see it, the planet was rising in twilight again. Around this time, Jupiter (mag. -1.5) emerged from the dawn twilight into the morning sky at the start of its 2017-18 apparition. It was 4º.5 to the ESE of Venus on November 9th, the gap between the two closing over the coming days. On November 10th Jupiter was 3º.5 to the ESE of Venus, on the 11th it was 2º.4 to the ESE and on the 12th it was 1º.3 to the South-east. At around 0610 UT on November 13th the two planets met in conjunction, Venus passing 0º.3 to the North of Jupiter. At the moment of conjunction the pair were positioned just 21' (0º.3) West of Virgo's border with Libra, the Balance or Scales, which Venus entered later that same day.

In the days following the conjunction, Venus pulled away Eastwards from Jupiter at average rate of 0°.9 per day and its solar elongation continued to reduce. By November 28th the planet was positioned just 10º West of the Sun and was increasingly difficult to view from most latitudes, observers at high-Northern latitudes losing sight of Venus from around this time.

Venus entered Scorpius, the Scorpion, on December 3rd and then Ophiuchus, the Serpent Bearer, on December 7th. From early December, observers at mid-Northern latitudes lost sight of Venus as it sank into the bright South-eastern horizon. Observers at Equatorial and Northern Tropical latitudes lost the planet from view by the middle of the month, bringing the 2017 morning apparition to a formal close.

Venus passed 2°.2 South of Mercury on December 15th in an unobservable planetary conjunction just 6° from the Sun. Mercury was now entering its seventh and final apparition of 2017, having undergone four morning apparitions and three evening apparitions during the year. The current morning apparition lasted through into January and slightly favoured Northern hemisphere observers.

Venus crossed the ecliptic heading Southwards on December 20th and entered Sagittarius, the Archer, on December 22nd. On December 25th Venus passed 1º.1 South of Saturn (mag. +0.5) in another unobservable planetary conjunction, this one taking place just 3°.5 West of the Sun. Venus attained its most Southerly declination for this apparition, at -23° 42' 32" (-23°.71 in decimal format), on December 28th.

Venus reached superior conjunction (passing behind the Sun as seen from the Earth) in Eastern-central Sagittarius on January 9th, positioned 0°.7 South of the Sun. The planet was now at a very distant 1.711 AU (255.9 million kms or 159 million statute miles) from the Earth. Were it to be visible from the Earth at this point, Venus would have had an apparent diameter of just 9".8 and would have shone at magnitude -3.8.

Having passed from the morning to the evening sky, Venus remained out of view - lost in the solar glare - for a further month, as it made its slow passage on the far side of its orbit from the Earth. The planet became visible once again from around early February 2018, when it was seen shortly after sunset from Equatorial latitudes as an 'Evening Star' in the WSW, heralding a new evening apparition of Venus (2018) which lasts through to October of that year.

[Terms in yellow italics are explained in greater detail in an associated article describing planetary movements in the night sky.]

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Venus Conjunctions with other Planets,

2017

Three conjunctions took place between Venus and other planets during the 2017 morning apparition.

The November 13th 2017 conjunction between Venus and Jupiter was a difficult one, taking place very late in the apparition when the pair were positioned just 14° from the Sun. Such a narrow elongation meant that the event took place in twilight, thus losing much of its visual spectacle. The Northern hemisphere was best placed to view it, though the pair's altitude when Jupiter disappeared from view was less than 10°.

A close conjunction between Venus and Mars took place on October 5th 2017. The small separation between the two planets (0°.2) allowed them to be fitted within the field-of-view of a telescope eyepiece at low or medium power. Adding to the spectacle was the star Leo (Sigma Leonis, mag. +4.0), which was positioned just 0°.3 to the NNE of Venus. The narrow solar elongation of the two planets (23° West) did however mean that the Red Planet was very distant and appeared no brighter than magnitude +1.8, almost as faint as it can get. The two planets were positioned in Leo, placing them at a low but observable altitude from Northern hemisphere locations before Mars was enveloped in the dawn twilight. From latitude 60° North the pair reached an altitude of 12° in the East when the Red Planet disappeared from view, whilst at mid-Northern latitudes they reached up to 15°. At latitudes South of the Northern Tropics the altitude at which Mars disappeared progressively reduced, until the pair were not seen at all South of ca. 33° South.

A Venus-Jupiter Conjunction sketched by Giovanni Isopi (Frosinone, Italy) as seen through an 8" SCT telescope at 80x magnification. The conjunction took place at dawn on August 18th 2014, the pair being separated by 0°.2. A similar conjunction between the two planets in November 2017 saw them positioned 0°.3 apart (click on the thumbnail for the full-size image, 27 KB) (Image: Giovanni Isopi)

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Venus and Uranus were involved in a relatively wide conjunction on June 2nd 2017. Uranus is a tricky object to observe whenever it is involved in conjunctions with Venus because Uranus is only just visible to the naked-eye and Venus is, of course, the brightest of the naked-eye planets. Consequently the glare caused by Venus' brilliance (mag. -4.2) made it difficult to see the much fainter Uranus (+5.9) beside it. In such events, binocular observers in particular may find it easier to position Venus just outside the binocular field of view so that Uranus may be more comfortably seen.

Twilight quickly renders Uranus unobservable (even through binoculars), so any conjunctions taking place less than about 20° from the Sun will be difficult or impossible to see. Fortunately, the 2017 conjunction took place only one day after Venus' greatest elongation date, hence it was about as far from the Sun as is theoretically possible. Despite this, however, only the Southern hemisphere was able to observe the conjunction with ease. Equatorial latitudes were best placed to observe it, the pair reaching an altitude of 32° in the East before the sky became too bright for Uranus to be seen. For much of the Northern hemisphere, the planets' location in Pisces meant that the angle of the ecliptic to the Eastern horizon at dawn was shallow, so that the conjunction was not visible at all North of mid-Northern latitudes.

The three planetary conjunctions with Venus which were viewable during the 2017 morning apparition are summarised in the table below.

Venus conjunctions with other planets during the 2017 morning apparition (click on the thumbnail for the full-size table, 34 KB)  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 Venus, e.g. on 2017 November 13, Jupiter was positioned 0°.3 South of Venus 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/S Lats' indicates that observers at latitudes further North than about 45°N (or further South than about 45°S) would most likely 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 and Morning visibility; the term Dawn refers specifically to the twilight period before sunrise, whilst the term Morning refers to the period 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 your particular latitude in the Rise-Set direction table.

The table is extracted from two other tables showing Venus conjunctions with other planets from 2010 to 2020 on the Venus Conjunctions page.

Although any given conjunction takes place at a particular instant in time, it is worth pointing out that, because of the planets' relatively slow daily motions, such events are interesting to observe for several days both before and after the actual conjunction date.

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 conjunction dates measured along the ecliptic are technically more accurate (separations between planets can be significantly closer) the Right Ascension method is the more commonly used, and it is the one which is adopted here.

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Moon near Venus Dates,

April to October 2017

The Moon is easy to find, and on one or two days in each month, it passes Venus in the sky. Use the following tables to see on which dates the Moon passed near the planet between April 2015 and October 2017:

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 appear closer to Venus when seen from some locations than others. For this reason, the dates shown in the table should be used only for general guidance.

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Credits

• The dates of Venus' constellation boundary crossings and its directions, altitudes and visibility durations were determined from the commercial software RedShift 5 by Maris Technologies Ltd. The planetary conjunction details and the times and separations of the lunar conjunctions with Venus (Moon near Venus dates) were obtained from RedShift 5 using the 'Conjunctions' option of the 'Sky Diary'.

• The information regarding the Mercury, Mars and Moon trio of september 18th 2017 was obtained from the website The Sky and Its Phenomena by Italian amateur astronomer Pierpaolo Ricci, as was the date of Venus' next highest declination (May 2020).

Copyright  Martin J Powell  March 2017