2025, September 4-9: Look for Venus and Sirius before Sunrise

September 4-9, 2025: Venus and Sirius shine at the same height above the horizon before sunrise. Look eastward in mid-twilight as the brightest planet and brightest star stand in the morning sky.

Venus with bright stars, September 18, 2020
Photo Caption – 2020, September 18: Brilliant Morning Star Venus appears with Sirius, Procyon, Castor, Pollux, Betelgeuse and Rigel.

by Jeffrey L. Hunt

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Venus and Sirius in Eastern Sky

Venus, Sirius before sunrise, September 4-9, 2025
Chart Caption – 2025, September 4-9: Venus and Sirius are the same altitude in the eastern sky during mid-twilight.

Venus and Sirius are at nearly the same altitude – height above the horizon – this morning and for the next few mornings. Step outside about 45 minutes before sunrise. Brilliant Venus shines in the east, while Sirius, the brightest star, sparkles in the southeast. The two are about 45° apart. Procyon, the Little Dog Star, is above an imaginary line between them, higher in the sky. Bright Jupiter stands nearly 25° to Venus’ upper right.

This predawn view has no astronomical importance, but it is a striking arrangement. After these few mornings at the same altitude, Venus is low in the sky and Sirius is higher. The star rises earlier each morning and appears higher than Venus at mid-twilight.

Venus in the Sky

Venus' Phases
Image Caption – Venus’ phases

Venus is descending toward its superior conjunction with the sun early next year. Through a telescope, the planet shows a morning gibbous phase, 85% illuminated. Its phases reveal that it revolves around the sun. Even through powerful telescopes or from spacecraft, the planet’s surface is hidden by a thick cover of clouds.

Venus Exploration

Venus from Galileo (NASA photo)
Photo Caption – Venus as viewed from the Galileo spacecraft (NASA photo)

Robot explorers have visited. In 1975, the Soviet Venera probe landed on Venus, surviving less than an hour in crushing heat and pressure. In 1990, NASA’s Magellan orbiter mapped the planet through the clouds, showing continents, volcanoes, and vast lava flows.

Sirius

Solar Spectrum
Photo Caption – This high-resolution spectrum of the Sun is a single image cut into segments to fit into this photo. The dark lines indicate the sun’s composition. (Credit: N.A.Sharp, NOAO/NSO/Kitt Peak FTS/AURA/NSF)

Sirius, in comparison, always appears as a pinpoint. Spectroscopy reveals its chemistry and temperature. Its distance is 9 light years, over 400,000 times farther away than Venus. This was measured by parallax, the small apparent shift of the star against the distant background when viewed from different points of Earth’s orbit.

Venus, moon, Sirius, August 14, 2020
Photo Caption – 2020, August 14, 2020: One day before their close grouping, the crescent moon is 13° to the upper right of Morning Star Venus. Sirius is making its first morning appearance in the east-southeast.

Sirius is the brightest star of Canis Major, one of Orion’s hunting dogs. Each August, it first appears before sunrise at mid-northern latitudes. In ancient Egypt, its rising marked the flooding of the Nile and the beginning of the agricultural year. Sirius also has a faint companion star, Sirius B.

Look eastward during the next few mornings to see Venus and Sirius at the same height above the horizon.

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