Inferior conjunction – Venus between sun and Earth

Chart showing orbits of Earth and Venus. — View larger. | As seen from the north side of the solar system, Venus (and all the planets) travel counterclockwise around the sun. Inferior conjunction – when Venus sweeps between the sun and Earth – happened last on June 3, 2020. It happens again on January 8-9, 2022. Illustration by John Jardine Goss/ EarthSky.

Venus in inferior conjunction

Venus travels one step inward from Earth in orbit around the sun. Its orbit is smaller than Earth’s. It has less distance to cover. And it moves faster in orbit (about 35 km/s in contrast to about 30 km/s for Earth). So Venus goes between us and the sun every so often. And, at such times, astronomers say it’s in inferior conjunction with the sun. Venus comes to inferior conjunction in 2022 at 1 UTC on January 9 (7 p.m. CST on January 8). Will you see Venus on the day of inferior conjunction? It’s not likely, unless you’re an extremely careful and experienced telescopic observer. After all, on the day of inferior conjunction, Venus will be crossing the sky with the sun during the day. More about when you’ll next see Venus below.

Venus, amidst its retrograde motion through the constellation Sagittarius, will comfortably pass north of the sun in our sky at the moment of inferior conjunction. It will pass just under 5 degrees from the sun. At the moment of inferior conjunction, Venus will officially shift from the evening to the morning sky for all observers on Earth.

Venus – our closest planetary neighbor and the brightest planet in our sky – passes between the Earth and the sun about every 19 months (1.6 years). So inferior conjunction for Venus happens that often.

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Cycles of Venus

The 1.6-year period – after which the position of Venus relative to the sun repeats, as seen from Earth – is called its synodic period.

Notice that 5 synodic periods of Venus add up to 8 years (just two-and-a-half days short). And so we have a cycle: inferior conjunctions of Venus that are 8 years apart happen at the same time of year, in the same part of the sky, with Venus at a similar angular distance from the sun, that is, the same apparent distance from the sun on the sky’s dome. Over time, this two-and-a-half-day variance will accumulate, so that the conjunctions “jump” into the previous month.

So inferior conjunctions of Venus strongly resemble each other on an 8-year cycle.

Two recent Venus transits, in June

The last passage of Venus between us and the sun happened on June 3, 2020. It was quite dramatic. Venus appeared in our sky within “touching distance” of our star. Venus missed the solar disk in 2020 by only a quarter of a degree.

So, in 2020, Venus fell short of transiting, or crossing, the solar disk as it had done 8 years earlier, on June 5, 2012 (and also 8 years before that, on June 8, 2004).

With the conjunctions of 2004 and 2012 resulting in transits, and the one in 2020 resulting in a near-miss, one could correctly conclude that the angular distance from the sun during these (currently) June series of inferior conjunctions is slowly but steadily increasing. And so they are. The June-May inferior conjunctions of Venus will not result in any more transits for many centuries.

Chart showing angular distance of Venus from sun at inferior conjunctions, 1996 to 2132. — Angular distances from Venus to the ecliptic (sun’s path in our sky) during June-May series of inferior conjunctions of Venus between years 1996 and 2132. The distances are shown in degrees. Boxes with a “T” mark the transits of Venus in 2004 and 2012. You can see that, in the June-May series, the angular distance between Venus and the sun is increasing. Hence no Venus transits to expect in June or May for centuries to come. Image via Milan B.

January transits of Venus

The inferior conjunction on January 8-9, 2022, does not carry the drama of its predecessor in June, 2020.

During the previous January inferior conjunction on January 10, 2014, Venus was around one-third of a degree farther from the sun than it is at the January 8-9, 2022, event. The next January conjunction of 2030 will fall even closer than 2022, at just 4.5 degrees. So one might assume that this January series is slowly inching (in astronomical terms) towards the sun.

And that would be a correct assumption. Venus is currently getting closer and closer to the sun on the sky’s dome at the January inferior conjunctions.

What’s more, as the conjunction of 2022 falls on the 8th day of January, the two-and-a-half day shift will cause this January series to shift into December relatively soon, in 2045. From that moment this, now-December series will result in closer and closer approaches to the sun in the second half of the century and in the early 22nd century the angular distance with the sun at the December inferior conjunction series will have decreased so much that it will bring us another pair of transits in years 2117 and 2125.

Some children alive today will likely live to see the Venus transits of the early 22nd century.

Chart showing angular distance of Venus from sun at inferior conjunction, 1998 to 2133. — Angular distances from Venus to the ecliptic (sun’s path in our sky) during the January-December series of inferior conjunctions of Venus between years 1998 and 2133. The distances are shown in degrees. The box marked “IC” indicates the current inferior conjunction on January 8-9, 2022. “T”-boxes mark upcoming transits of Venus in 2117 and 2125. Image via Milan B.

For experts, seeing Venus morning and evening

Keen observers located north of the 40 N. latitude might be able to spot Venus as both an evening star and a morning star on the same day. The best day for this interesting phenomenon is January 8, although one day before or after, this celestial geometry will be nearly as good. Of course, extreme safety precautions are the rule when attempting to observe any object so close to the sun.

Please do not attempt to observe Venus near the sun unless you’re an experienced sun observer.

Star chart with a lower green section depicting the section of the sky below ground. One bright light (sun) with a yellow line depicting its path on the sky, and a lesser bright (Venus) to its north. — View larger. | This chart shows the position of Venus 30 minutes after reaching the same right ascension as the sun. At that time, it is positioned directly north of the sun. It rises before and sets after the sun for observers at mid- to high-northern latitudes. The positions of Venus and the sun are shown here as seen from southern British Columbia and northern Washington state on January 8, 2022, the inferior conjunction date for observers in North America. Image via Sky Safari/ Milan B.

2 images side-by-side of the extremely thin crescent Venus close to conjunction. — View larger. | The planet Venus, about 8 hours before the January 11, 2014 inferior conjunction. The daylight hemisphere of the planet is facing almost entirely away from Earth. Photo by EarthSky Facebook friend Shahrin Ahmad in Malaysia. Thank you, Shahrin!

When will you next see Venus?

Otherwise, you can expect to see Venus come back to the morning sky – east before sunrise, as seen from all parts of the globe – this month. Since Venus is the brightest planet, you’ll be able to spot it low in the east, near the sunrise point, not long before the sun comes up. Venus will surprise you with its brightness so low in the sky! In fact, by the end of January 2022, Venus will be heading for another greatest brilliancy in early February.

Watch for it in the last half of January!