2023, April 18: Plan Sidereal Vacation, Evening Planets

April 18, 2023: Plan a trip to a location to see the Milky Way.  Read on to consider the factors.  The evening planets continue their nightly performances.

Perseid Meteor Shower
In this 30 second exposure, a meteor streaks across the sky during the annual Perseid meteor shower Friday, Aug. 12, 2016 in Spruce Knob, West Virginia. Photo Credit: (NASA/Bill Ingalls)

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by Jeffrey L. Hunt

Chicago, Illinois:  Sunrise, 6:06 a.m. CDT; Sunset, 7:35 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.

Plan a sidereal or starry vacation during the northern hemisphere’s warmer months, especially to see the Milky Way arcing across the sky from the southern horizon, to the north-northeast horizon.

Some state and national parks have nighttime observing with telescopes.  Check on the availability to look see the celestial wonders up close.

When planning, three factors are important:  Sky brightness, moonlight, and latitude.

This composite image shows a global view of Earth at night, compiled from over 400 satellite images. (NASA photo)
Photo Caption – This composite image shows a global view of Earth at night, compiled from over 400 satellite images. (NASA photo)

First, finding a dark location is necessary to see the dim wonders of our galaxy.  Perpetual outdoor lighting ruins views of a dark sky and the Milky Way.  Even a visit to an urban or suburban location may allow for a jaunt to the countryside to see the nighttime views.

Second avoid the moon.  Bright moonlight can have the same effects on the Milky Way as outdoor lighting.  That light whitewashes sights of the dim star clouds and gaseous nebulae.

When Scorpius and Sagittarius are in the southern sky, the Milky Way arches toward the north-northeast.
Chart Caption – When Scorpius and Sagittarius are in the southern sky, the Milky Way arches toward the north-northeast.

Seeing the Milky Way depends on the month when the Sagittarius and Scorpius region are in the south.  During May when the region is in the south and without the moon, the dates are May 13-27, 2.5-3 hours before sunrise.  During June, this occurs June 14-24, 4-5 hours before sunrise.  The scene occurs again, July 9-21, at the end of evening twilight, about two hours after nightfall.  For August, the conditions occur August 5-19, at the end of evening twilight.

The Perseid meteor shower peaks during predawn hours of August 13.  The moon is only 8% illuminated on that morning.  As with Milky Way sightings, a dark location is preferred, although a few meteors can be seen from urban and suburban areas.

Latitude is the final factor.  During the spring and summer months, northern latitudes do not experience darkness. They have long daylight and twilight, no total darkness.  For example, for Juneau, Alaska, from April 27th through August 15th, the location has no darkness.

Taking a cruise to Alaska? You won’t see the Milky Way or northern lights (aurora borealis) during the summer. For latitudes farther north than 49° north latitude, locations have some periods of twilight at midnight.  For example, from Vancouver, British Columbia, residents experience midnight twilight and no darkness during June and July.  Farther northward, twilight occurs longer as noted above for Juneu, Alaska.

Take along a binocular to investigate the Milky Way’s wonders.

Summaries of Current Sky Events
SUMMARY FOR VENUS AS AN EVENING STAR

Here is today’s planet forecast:

Morning Sky

2023, April 18: Saturn is in the east-southeast before sunrise.
Chart Caption – 2023, April 18: Saturn is in the east-southeast before sunrise.

Saturn is the lone bright planet in the morning sky.  At forty-five minutes before daybreak, the Ringed Wonder is over 10° above the east-southeast horizon.  It appears higher in the sky each morning.

The moon is nearing the New Moon phase tomorrow at 11:12 p.m. CDT.  Then it appears in the evening sky after sunset.

Jupiter is slowly appearing in the morning, but it is still immersed in bright sunlight.  It makes the first morning appearance next month.

Evening Sky

2023, April 18: Venus and Mercury are in the western sky after sundown.
Chart Caption – 2023, April 18: Venus and Mercury are in the western sky after sundown.

Brilliant Venus is in the western sky after sundown and easily mistaken for lights on a low-flying airplane.  At forty-five minutes after sundown, the planet is nearly 30° above the western horizon. 

The Evening Stars steps eastward in front of Taurus’ distant stars.  Tonight the planet is 7.5° to the upper right of Aldebaran and 9.0° to the upper left of the Pleiades star cluster.  It is out of the same binocular field with Taurus’ brightest star and the stellar bundle.

2023, April 18: Through a binocular, Venus appears against some Hyades star cluster outliers.
Chart Caption – 2023, April 18: Through a binocular, Venus appears against some Hyades star cluster outliers.

Through a binocular, Venus is in a rich Taurus starfield that includes some Hyades cluster outliers. The Hyades is a star cluster to the lower left of Venus.  The star bunch along with Aldebaran make a letter “V” outlining the head of Taurus.  Epsilon Tauri (ε Tau on the chart) is at the top of the letter opposite Aldebaran. Typically the bright stars are named with Latin, Greek, or Arabic names.  These dimmer stars are named with Greek letters.  This evening the brilliant planet is 0.9° to the upper right of Upsilon Tauri (υ Tau).  Watch the planet step toward Tau Tauri (τ Tau) during the next several evenings.

Mercury is less than 10° above the horizon and nearly 25° to the lower right of Venus. Now a binocular object, the planet is difficult to see in the blush of bright evening twilight.  It is lower in the sky and dimmer since it appeared at greatest elongation a week ago. 

Mercury is quickly closing on our planet on an inside orbital path.  It passes between Earth and the sun on May 1st, heading toward the morning sky.  Its spring morning appearance is unfavorable, rising only an hour before sunrise.  At its best, the planet is just above the eastern horizon at 45 minutes before sunrise.  It is higher as the sky brightens, but best viewed through a binocular.

2023, April 18: Mars appears against Gemini during the evening hours.
Chart Caption – 2023, April 18: Mars appears against Gemini during the evening hours.

At this hour, Mars – marching eastward in front of Gemini – is over 33° to the upper left of Venus.  The Red Planet is high in the west-southwest.  Wait until the end of twilight, about 90 minutes after nightfall, to see Gemini’s dimmer stars.

Mars is dimming as the distance to Earth increases.  Tonight, it is dimmer than Pollux, but brighter than Castor.

At the end of twilight, Castor and Pollux, the Gemini Twins are high in the western sky with Mars over 11° to the lower left of Castor and 2.3° to the upper left of Mebsuta.

Mars is heading generally toward Pollux, passing in a wide conjunction on May 8th.

Continue to watch the evening planets move against the starry background.  Soon we say “Goodbye!” to Mercury after its best evening appearance of the year, while Venus moves through Taurus, closing the gap to Mars.

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