In the last months of last year and at the beginning of this year, the planet Venus, contrary to its poetic definition of “Morning Star,” adorned the evening sky. In cloudless weather, people with good eyesight could see it with the naked eye before sunset. On January 10, it passed through the configuration of the greatest eastern elongation and moved away from our luminary by 47°, after which it began to approach it, simultaneously approaching the Earth in space. In the next few days, the morning visibility of Venus will finally begin, but its evening visibility… will not end! How long will it last, why will it happen, and how often does it happen?
A rare phenomenon, currently available only in the northern hemisphere
Of all the major planets in the Solar System, Venus comes closest to Earth: the minimum distance to it can be 0.26 AU, or less than 39 million km (about a hundred times the average distance between Earth and the Moon). Such conjunctions occur during configurations known as “lower conjunction”, which repeat on average every 584 days. If the orbits of our planets were in the same plane, ground-based observers could see Venus against the Sun at this time. In reality, such phenomena – also called “transits” – are quite rare, as they require a lower conjunction to occur near the line of intersection of the orbital planes, i.e. the line of nodes. The last time this happened was in 2004 and 2012, and the next transit of Morning Star is expected in 2117.
This is because the Venusian orbit is inclined to the Earth’s by 3.4°. Therefore, during the lower conjunctions, Venus most often passes north or south of the Sun (from the point of view of the inhabitants of our northern latitudes – “above” or “below”). Since the average heliocentric distance of this planet is 0.723 AU, using simple trigonometric formulas, we can calculate that its maximum distance from the ecliptic plane can be 0.0428 AU or 6.4 million km. But if the Earth is at the minimum possible distance from Venus at this time, it means that the apparent angle of its deviation from this plane from our point of view will be almost three times greater and will exceed 9°!
Of course, such large deviations of Venus from the ecliptic do not occur very often, but in fact, this distance does not have to be the maximum for the phenomenon described to occur. At approximately 7:00 p.m. GMT (2:00 p.m. EST) on March 20, 2025 – the day of the vernal equinox – the direct ascension of Venus and the Sun will be equal, with the latter’s declination being 9.3° less. If we were to make observations at the equator, this would give us nothing: the planet would hide behind the horizon and appear above it at the same time as the daylight. But the farther north it is, the later it sets relative to the Sun and the earlier it rises.
How to see Morning Star and Evening Star in one day
At Kyiv’s latitude, the difference between the rising and setting of Venus and the Sun on March 20 will be about 40 minutes. In practice, this will mean that 10-15 minutes after the upper edge of the solar disk disappears behind the horizon when the brightness of the sky has already decreased sufficiently, Venus will still be at an altitude of 4-5° (and 9-10° to the right of the sunset point). However, you can start searching even earlier – as soon as the Sun disappears behind the horizon. Due to its high apparent brilliance, it will be easy to see, the main thing is to have an open western horizon. Even with small binoculars, you can see that the planet looks like a thin, shining sickle.
To notice the rising of Venus (on March 20 in Kyiv, it is expected at 3:18 a.m. GMT (10:18 p.m. EST), on March 21 – 5 minutes earlier), you need to be more attentive, because you will not be able to “catch” the place of sunrise, which is difficult to predict in advance. Of course, “double visibility” will not be limited to one day. It will begin on March 18, when the Morning Star will still be better visible in the evening, and will end on March 23. On that day, at 8:00 a.m. GMT, the angular distance between the planet and the center of the star will decrease to a minimum of 8°24′. This will be the moment of Venus’s true lowest conjunction. After that, it will remain in the morning sky for a long time and will fully justify its poetic name until the beginning of autumn.
The relative positions of Venus, the Earth, and the Sun in space are almost exactly repeated with a period of 8 years. Therefore, it is possible to predict when the “new season” of its double visibility in our latitudes will come. This will happen in March 2033. It is also easy to understand that similar periods of visibility of the Morning Star occur in the Southern Hemisphere. In our era, they occurred in mid-August in 2007, 2015, 2023, and 2031. It is clear that we then have a long period of its “invisibility” (when Venus disappears behind the horizon before the Sun, and rises, on the contrary, later). But on August 11, 1999, one of these periods was unexpectedly interrupted – on that day, a total solar eclipse occurred in Europe and the Middle East, and bright stars “appeared” in the darkened sky, among which the nearest planet shone brightest…
