May 15, 2023: A thinning crescent moon is visible in the east-southeast before daybreak. Venus appears to be chasing Mars through Gemini after sundown.
by Jeffrey L. Hunt
Chicago, Illinois: Sunrise, 5:31 a.m. CDT; Sunset, 8:04 p.m. CDT. Check local sources for sunrise and sunset times for your location. Times are calculated by the U.S. Naval Observatory’s MICA computer program.
Summaries of Current Sky Events
Here is today’s planet forecast:
Morning Sky
This morning a lovely waning crescent moon, 20% illuminated, is about 10° above the east-southeast horizon. Find a clear view in that direction.
Saturn is over 20° up in the southeast and over 25° to the upper right of the lunar crescent at an hour before daybreak.
The moon nears the New moon phase on the 19th at 4:53 p.m. CDT. Until then, each morning it is lower in the eastern sky with a thinning crescent. In two mornings, it is near Jupiter. From across the U.S., Canada, and Greenland, the lunar disk occults or eclipses the Giant Planet.
The occultation is a daytime event for eastward time zones, beginning at 6:36 a.m. CDT in Chicago. Jupiter and the crescent moon are bright enough to be seen during daylight and the event can be tracked with a spotting scope or binocular. Jupiter reappears at 7:40 a.m.
Jupiter is emerging from bright sunlight into a darker morning sky, after its conjunction with the sun. At forty minutes before sunrise, the Jovian Giant is nearly 4° above the horizon and nearly 30° to the lower left of the moon.
Mercury is speeding toward the morning sky as well, but its appearance is unfavorable. At its best, early next month, the planet rises only an hour before the sun. This morning, Mercury is bathed in bright sunlight when it is high enough to be seen.
Evening Sky
Brilliant Venus continues as the spectacle in the western sky after sundown. Still growing in brightness each evening, find it about one-third of the way up in the sky from the horizon to overhead at 45 minutes after sundown.
The planet is stepping eastward in front of Gemini, 1.1° to the lower right of star Mebsuta, also known as Epsilon Geminorum (ε Gem on the chart). The Evening Star is below the Twins, Castor and Pollux.
Through a telescope, Venus is an evening gibbous phase, that is 60% illuminated. The phase is shrinking but the term “waning” is not similar to the waning lunar cycle. Venus’ evening half phase, looks like the moon’s First Quarter phase. For the moon, it wanes from gibbous to Last Quarter moon phase. So using waxing, waning, first quarter, and last quarter are not representative of Venus’ phase cycle. So, either Venus is in the morning sky or evening sky. The phase is crescent, gibbous, or half. The current descriptive term for its phase is evening gibbous. The planet reaches its half-full phase and its greatest elongation – separation from the sun – early next month.
Mars is over 18° to the upper left of Venus and 6.4° to the lower left of Pollux. The Red Planet is dimmer than Pollux and about the same brightness as Castor.
Mars marches eastward against the starfield at about half Venus’s speed. In two evenings, Mars lines up with Pollux and Castor. Extend an imaginary line from Castor through Pollux. The alignment occurs when Mars is at that line.
At this rate, Venus overtakes Mars. When does that occur? This reads like one of those train problems from algebra class (If the red train leaves the station at 10 a.m. heading eastbound at 50 miles per hour . . .) Stay tuned here. There is an interesting conclusion to this chase.
Return to the evening sky about 90 minutes after sundown, during late twilight. The dimmer stars of Gemini are easily seen. The pattern makes two side-by-side stick figures, with Castor and Pollux dotting the heads. Venus and Mars shine against that sidereal backdrop.
During the next few mornings, watch the moon approach Jupiter, and during evening hours, Venus continues to overtake Mars.
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