2025, February 14: Venus Greatest Illuminated Extent

February 14, 2025: Evening Star Venus shows its largest illuminated area, the greatest illuminated extent, as it approaches greatest brilliancy.

Venus, Moon, February 1, 2025
Photo Caption – 2025, February 1: Venus and crescent moon after sunset.

by Jeffrey L. Hunt

Chicago, Illinois: Sunrise, 6:47 a.m. CST; Sunset, 5:23 p.m. CST.  Check local sources for sunrise and sunset times. Times are calculated by the US Naval Observatory’s MICA computer program.

Venus Gleams from Southwestern Sky

Venus, Saturn, February 14, 2025
Chart Caption – 2025, February 14: Venus and Saturn shine from the west-southwest after sunset.

Step outside during the evening.  Brilliant Venus shines from the west-southwest, dominating the sky.  This is from Venus’ proximity to Earth.  Moving on an orbit inside Earth’s slightly elliptical pathway, Venus passes between Earth and Sun next month.

As Venus alternates from morning sky to evening sky and back to morning again, its distance varies.  When Venus passes between the sun on March 22nd, it is only 26 million miles from Earth.  When it was near superior conjunction on the far side of the sun last spring, it was 218 million miles away. Tonight, Venus is less than 40 million miles from Earth.

Venus’ Apparent Diameter and Phases

Earth, Venus distances, illuminations
Chart Caption – The orbits of Earth and Venus are displayed to show various distances between the planets throughout a Venusian apparition.

Throughout its orbit, Venus is illuminated by the sun and it displays phases through a telescope.  When at superior conjunction and farthest from Earth, it is near the full phase.  Moving faster, Venus’ phase then displayed a gibbous, a half-full phase, and now a crescent phase.

Additionally, the planet’s diameter through a telescope is nearly four times larger.  This seems counter to our thinking when we consider the moon.  With about 15%, the moon’s diameter is fairly constant through a lunation.  The Full moon phase is larger than the waxing crescent phase.  The lunar globe is the same size, the illuminated portion varies.

Greatest Illuminated Extent

Venusian illuminations
Chart Caption – 2025, February 14: This hand-drawn image shows the relative sizes of Venus’ illumination when it is close to Earth and far away. Tonight’s crescent phase covers the most area of the sky of the Venusian phases.
Venus' Phases
Image Caption – Venus; phases

For Venus the apparent size varies greatly so that the size of the illuminated portion is varies as well.  The largest illuminated portion of the moon occurs tonight when the moon is 27% illuminated.  The hand-drawn diagram attempts to show this effect comparing the size of the illuminated planet on June 10, 2024, when it was far from Earth compared to tonight when it its considerably closer.  Since tonight’s crescent is largest, it covers the most area of the sky for any Venusian phase, and so the name greatest illuminated extent.

We might think that Venus should be brightest tonight, since this is the largest illuminated portion of the planet we see and it is close to us.  The planet is not a perfect reflector and so the night of greatest brilliancy can occur within four or five nights of this event. For this Venusian cycle, the night of greatest brilliancy is February 18th, though our eyes may not see much difference across the four nights.

Step outside tonight to see the brilliant planet gleam.  If you have a telescope, take a look at Venus’ greatest illuminated extent.

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