2025, January 9:  Venus at Greatest Elongation

January 9, 2025:  Venus is at greatest elongation, its largest separation from the sun.  It brightens throughout the month.

Venus, Saturn, Moon, November 3, 2016
Venus, Saturn, Moon, November 3, 2016

by Jeffrey L. Hunt

Venus is at greatest elongation tonight, 47.2°.  It is farthest from the sun during this appearance, setting nearly four hours after nightfall.

Evening Venus

The Evening Star gleams brightly from the southwestern sky after nightfall on this evening as the gibbous moon occults the Pleiades star cluster in the eastern sky.  Venus is bright enough to be seen during the daytime, but it is easily observed 30 minutes after sunset.

During the month, Venus brightens over 30%, reaching its brightest on Valentine’s evening.

Venus' Phases
Image Caption – Venus’ phases

This evening through a telescope, the planet’s phase is 50%, an evening half phase.  Waxing and waning are not used to describe Venus’ phases, as it do not display similar phase cycles to the moon.  Evening and morning are used for Venus’ phases, rather than the lunar descriptors.

Venus Approaches Saturn

Venus at Greatest Elongation
Chart Caption – 2025, January 9: Venus and Saturn are in the southwestern sky after sunset.

An hour after sunset, Venus is less than 30° up in the southwest and 8.2° to Saturn’s lower right.  The brilliant planet overtakes the Ringed Wonder on the 18th.

Venus at Greatest Elongation

Venus at Greatest Elongation
Chart Caption – 2025, January 9: The Sun-Earth-Venus angle is at its largest. Venus is at greatest elongation, appearing farthest from the sun tonight.

In simple geometry, the Sun-Earth-Venus angle is at its maximum angle for this Venusian appearance.  Additionally, if the planets’ orbits were perfect circles, the Earth-Venus line is tangent to the Sun-Venus line.

Using a right triangle, Venus distance from the sun can be calculated as a fraction of Earth’s distance, resulting in a Sun-Venus distance of 73% of Earth’s solar distance.

Jupiter and Moon

Moon-Pleiades occultation
Chart Caption – 2025, January 9: The bright gibbous moon is to Jupiter’s upper right and near the Pleiades star cluster.

Farther eastward, the gibbous moon, 82% illuminated, is near the Pleiades star cluster – nearing the occultation of its bright stars – and 13.6° to Jupiter’s upper right.

Jupiter is retrograding in front of Taurus.  While moonlight washes out the constellation’s dimmer stars, the Jovian Giant is 5.4° to Aldebaran’s upper right, the Bull’s brightest star, that is about the same color as Mars.

Mars in East-Northeast

Venus at Greatest Elongation
Chart Caption – 2025, January 9: Two hours after sunset, Mars is in the east-northeast below the Gemini Twins.

Mars is visible at this hour, low in the east-northeast.  Wait another 60 minutes to see it over 15° above the horizon and 5.6° below Pollux, one of the Gemini Twins.

The Red Planet retrogrades in front of Cancer.  The Earth-Mars closest approach occurs in three nights and opposition on the 15th.

Mars is the fourth brightest starlike body in the sky tonight, following Venus, Jupiter, and Sirius, the Dog Star.  While this planet rivals Sirius’ brightness, it appears dimmer to the human eye from its reddish tint.

Four Planets on Display

The four bright evening planets span an arc of 140° from Venus in the south-southwest to Mars in the east-northeast.

This month has ongoing celestial activity with tonight’s occultation, the moon’s eastward trek, Venus’ pending conjunction with Saturn, and Mars retrograde and opposition.  Take a look each clear evening.

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