Home > Concepts, Ephemeris Program, Observing > Ephemeris: 09/04/2025 – Venus, the Morning Star

Ephemeris: 09/04/2025 – Venus, the Morning Star

September 4, 2025

This is Ephemeris for Thursday, September 4th. Today the Sun will be up for 13 hours and 4 minutes, setting at 8:13, and it will rise tomorrow at 7:10. The Moon, 3 days before full, will set at 4:19 tomorrow morning.

Venus graces our morning sky as the Morning Star. It is seen, this year, along with the planet Jupiter. They are the two brightest planets. The Greek and others of that part of the world, early on, thought the evening and morning appearances of Venus were two different planets. The Mayans of Pre-Columbian Central America were meticulous observers of Venus, as is seen in one of their surviving books, the Dresden Codex. A Venus cycle lasts 584 days, from first appearance in the morning sky, its heliacal rising, through its morning appearance, disappearance behind the Sun, through its evening appearance and disappearance to the next heliacal rising. Astronomers call that it’s synodic period. Five synodic periods equal almost exactly 8 years.

Addendum

The Venus Cycle as seen by the Mayans.
The Venus Cycle as seen by the Mayans. In the gray part of the cycle Venus in unobservable due to being too close to the Sun in the sky.
Perspective view of Venus’ orbit in relation to the Earth, showing change in phase and size with position. When Venus is on the right side of the Sun, it is visible in the morning sky, on the left in the evening. The numbers represent Venus’ apparent size in seconds of arc. The image was found on the Internet, uncredited from a defunct website.
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