September 12, 2023: Venus and Sirius are visible in the eastern sky during morning twilight. The moon gathers with Venus and Regulus before daybreak.
by Jeffrey L. Hunt
Chicago, Illinois: Sunrise, 6:28 a.m. CDT; Sunset, 7:06 p.m. CDT. Check local sources for sunrise and sunset times. Times are calculated by the US Naval Observatory’s MICA computer program.
Summaries of Current Sky Events
Here is today’s planet forecast:
Morning Sky
Step outside an hour before sunrise to see brilliant Morning Star Venus nearly 20° up in the east. It continues its rapid entry into the morning sky, gaining three minutes of rising time each morning compared to sunrise during the next week. Venus is at the same altitude – height above the horizon – as Sirius, in the southeast.
The Dog Star is nearly 40° from the ecliptic, the plane of the solar system, where the planets move against the background stars. From this great distance, Venus does not have a close conjunction with the star, but they stand in the eastern sky during morning twilight, the brightest planet and brightest star. This continues for the remainder of September. During October and later, Venus is limited to its western travel, but Sirius appears farther westward and higher in the sky during morning twilight.
While looking at the bright stars this morning, find the crescent moon, 6% illuminated, and nearly 13° to the lower left of brilliant Venus and 9.5° above Regulus, Leo’s brightest star.
The moon reaches the New moon phase on the 14th at 8:40 p.m. CDT.
This morning, look for earthshine, reflected sunlight from Earth’s oceans, clouds, and land, that softly illuminates the lunar night. Photograph it with a tripod-mounted camera and use exposures up to a few seconds.
Through a spotting scope or telescope, Venus displays a crescent phase, 21% illuminated. The crescents are tilted toward the sun, with the horns pointed away. Because Venus is emerging from sunlight into the morning and the phase is growing, the Venusian phase is named “morning crescent.”
Jupiter, the third brightest celestial body in the sky this morning after the moon and Venus, is high in the south-southwest. It retrogrades, an illusion from Earth lapping the more-distant world, against Aries, 13.5° to the lower left of Hamal, the Ram’s brightest star, and nearly 16° to the lower right of the Pleiades star cluster, on Taurus’ back.
Look at the planet with a binocular. If held steadily, up to four of Jupiter’s moons are visible, resembling stars near the planet. Ganymede and Io are east of the planet this morning, while Europa and Callisto are to the west.
Mercury is moving quickly into the morning sky. Rising about fifty minutes before the sun, it is not far enough from the sun’s glare to be seen.
Evening Sky
Unlike Mercury in the morning, Mars is on a very slow slide toward solar conjunction during November. It sets fifty minutes after nightfall.
Saturn is the first bright planet to be seen this evening. Rising before sundown, the planet is nearly 25° up in the southeast at two hours after sunset. It retrogrades, moves westward compared to the starry background, in front of Aquarius, 9.2° to the upper right of Skat, and 9.4° to the right of Lambda Aquarii (λ Aqr on the chart).
The star Fomalhaut is about 20° below the Ringed Wonder and over 5° above the horizon.
Through a binocular, Saturn is not much of a view. The rings showing as tiny extensions might appear next to the planet, if the binocular is held firmly. Of course, the best views are through a telescope. At about 80x magnification, the rings are visible along with some of its moons. Titan is to the east of the planet this morning. At higher magnifications the ring structure can be seen as well as some subtle cloud bands, although not as distinct as the banding in Jupiter’s atmosphere.
Saturn is in the south around midnight. It fades into the atmospheric layers near the horizon that blurs and dims celestial objects during morning twilight.
Jupiter rises in the east slightly over two hours after the sun sets. By tomorrow morning it is again high in the south-southwest.
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