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Venus at its brightest in late April

Late April 2020 presents the planet Venus at its brightest as the evening “star” for all of this year. No matter where you live worldwide, look west after sunset to marvel at this brilliant beauty lighting up the evening dusk first thing after sunset. Given clear skies, it’ll be almost impossible to miss Venus, the third-brightest celestial body in all the heavens, after the sun and moon, respectively.

At its brightest, Venus is nearly 3 times brighter than at its faintest. Even so, Venus always ranks as the second-brightest heavenly body in the night sky, easily outshining all other planets and stars. Venus’ reign in the evening sky started on August 14, 2019, and will come to an end on June 3, 2020. But these next several days, at dusk and early evening, Venus will be shining at her brightest best in the evening sky.

Chart showing Northern Hemisphere track of Venus from August 2019 to June 2020.

Chart by Guy Ottewell via his blog. The chart depicts Venus’ disk size and phase in the evening sky from superior conjunction (August 14, 2019) to inferior conjunction (June 3, 2020).

On April 28, 2020, at 1:00 Universal Time (April 27, 2020, at 8 p.m. CDT), Venus reaches what is called its greatest illuminated extent – at which juncture the illuminated portion of Venus covers the greatest square area o the sky’s dome. It is at or near greatest illuminated extent that Venus shines at its maximum magnitude.

Although you need a telescope to view Venus’ disk and changing phases, Venus’ disk is smallest when Venus first enters the evening sky at full phase (superior conjunction). (See the diagram below.) Superior conjunction last happened on August 14, 2019, when Venus was on the far side of the sun and farthest from Earth. Moreover, this was when Venus was in the sun’s glare and not yet visible in Earth’s evening sky.

Earth's and Venus' orbits

Earth and Venus orbit the sun counterclockwise as seen from the north side of the solar system. Venus reaches its greatest eastern elongation in the evening sky about 72 days before inferior conjunction and its greatest western elongation in the morning sky about 72 days after inferior conjunction. Greatest illuminated extent for Venus comes midway between a greatest elongation and an inferior conjunction.

Venus’ disk is largest when Venus leaves the evening sky some 292 days later at new phase (inferior conjunction). However, the dark side of Venus is facing Earth, and Venus (like at full phase) is again lost in the sun’s glare. Inferior conjunction will next happen on June 3, 2020.

It might be hard to believe, but Venus shines at its brightest in our sky when she’s displaying a crescent phase (approximately 25 percent illuminated). It’s as a crescent that Venus’ daytime side, or illuminated side, covers the maximum area of sky. It’s at or near greatest illuminated extent that Venus appears brightest in our sky.

Here is a collection of Venus images from December 2016 to February 2017 showing how the size and phase of Venus has changed as it starts to move between the Earth and the Sun. Eventually, Venus will pass between the Earth and sun and emerge into the morning sky once again. Image via our friend Tom Wildoner at LeisurelyScientist.com.

Venus’ greatest illuminated extent in the evening sky (April 28, 2020) always happens about 36 days after Venus reaches greatest eastern (evening) elongation (March 24, 2020), and some 36 days before Venus sweeps to inferior conjunction (June 3, 2020). At its greatest elongation, in either the evening or morning sky, Venus’ disk is approximately 50 percent covered over in sunshine.

On the other hand, Venus’ greatest illuminated extent in the morning sky (July 10, 2020) comes some 36 days after inferior conjunction (June 3, 2020) yet 36 days before reaching greatest western (morning) elongation (August 13, 2020).

Let the golden triangle help you to remember these Venus’ milestones. The two base angles equal 72 degrees and the apex angle equals 36 degrees. Quite by coincidence, Venus’ greatest elongations happen some 72 days before and after inferior conjunction, and Venus’ greatest illuminated extent happens some 36 days before and after inferior conjunction.

Golden Triangle

The Golden Triangle, with the apex angle = 36 degrees and base angles = 72 degrees

Look west after sunset to behold dazzling Venus, the sky’s brightest planet shining at her brightest best in the evening sky!

Bruce McClure