2024, May 11: Sirius Heliacal Setting

April 25, 2018: Venus and Sirius
Photo Caption: April 25, 2018: Venus and Sirius

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by Jeffrey L. Hunt

Chicago, Illinois: Sunrise, 5:34 a.m. CDT; Sunset, 8:01 p.m. CDT.  Check local sources for sunrise and sunset times. Times are calculated by the US Naval Observatory’s MICA computer program.

Sirius Heliacal Setting

Sirius Heliacal Setting
Chart Caption – 2024, May 11: Sirius and some of winter’s evening stars are disappearing into bright evening twilight.

Bright Sirius and some stars that shine brightly during winter’s evenings are making their last appearances or heliacal settings.  Then they disappear into bright sunlight.  Sirius reappears in the morning sky during mid-August.

At 45 minutes after sunset, bright Sirius is low in the west-southwest.  It shines through the colorful whisps of evening’s light.

The last appearance depends on local conditions, weather and obstacles at the horizon.  The date can vary depending on the clarity of the sky.

Orion’s Bellatrix, considerably dimmer than Sirius, is slightly higher in the west, joins the departure.  It reappears during July.

Topaz Aldebaran, Taurus’ brightest star in the west-northwest, is disappearing into evening twilight as well. Like Mars in the morning, its color blends with twilight and may be difficult to see already.  This star reappears in the eastern morning sky during late June.  Jupiter is in the region when Aldebaran’s heliacal rising occurs.

Summaries of Current Sky Events
Summary for Venus as a Morning Star, 2023-24

Here is today’s planet forecast:

Morning Sky

Morning Planets

Four bright planets are west of the sun and considered morning planets.  Venus rises only 12 minutes before the sun.  It is immersed in bright twilight.

Mercury, rising 52 minutes before the sun, is slightly above the eastern horizon at 30 minutes before sunrise.  It is veiled in morning twilight.  Southern hemisphere sky watchers have an excellent view of the planet.

Saturn and Mars

2024, May 11: Mars and Saturn are visible in the eastern sky before sunup.
Chart Caption – 2024, May 11: Mars and Saturn are visible in the eastern sky before sunup.

An hour before sunrise, Saturn is visible, nearly 15° above the east-southeast horizon. The planet is not bright like Venus or Jupiter, although it is brighter than most stars in the sky this morning.

Mars is less than 10° up in the east and over 20° to Saturn’s lower left.  The Red Planet seems to struggle to make it out of morning twilight.  Use a binocular to see it.

Evening Sky

Evening Moon

2024, May 11: An hour after sundown, the crescent moon is below the Gemini Twins, Castor and Pollux. Procyon and Capella are in the western sky as well.
Chart Caption – 2024, May 11: An hour after sundown, the crescent moon is below the Gemini Twins, Castor and Pollux. Procyon and Capella are in the western sky as well.

The crescent moon, 20% illuminated, is in the western sky after sunset, above winter’s disappearing stars.  The lunar orb is in front of Gemini this evening, part of winter’s contingent that disappears into sunlight next month.

2023, January 23: The crescent moon, Venus, Saturn after sundown.
Chart Caption – 2023, January 23: The crescent moon, Venus, Saturn after sundown.

Again, this evening, look for earthshine on the moon’s night portion, between the lunar cusps or horns.  The effect is from sunlight reflecting from Earth’s oceans, clouds, and land.

Gemini’s Castor is 10.1° to the moon’s upper left.  The second Twin, Pollux, is 4.5° to the left of Castor.  Tomorrow evening, the moon is next to Pollux.

Procyon, the Little Dog Star, is nearly 30° above the west-southwest horizon and to the lower left of the Twins and the lunar crescent.

Capella is nearly 30° to the lower right of the moon and almost 30° above the northwest horizon.

Notice that an imaginary arc connects Procyon, Pollux, Castor, and Capella, making an imaginary umbrella in the western sky.

This evening the moon sets over four hours after sundown and after midnight.

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