2023, June 18: Longest Day, Venus Eastward Trek

June 18, 2023: Today and tomorrow mark the days of longest daylight for the year.  Venus continues its eastward trek near Leo after sundown.

PODCAST FOR THIS ARTICLE

by Jeffrey L. Hunt

Chicago, Illinois:  Sunrise, 5:15 a.m. CDT; Sunset, 8:29 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.

Today and tomorrow, in Chicago, daylight reaches its greatest length, fifteen hours, fourteen minutes.  Add four hours, twenty-four minutes for twilight, darkness – the time between the end of evening twilight and the beginning of morning twilight is four hours, twenty-two minutes long.

Here is today’s planet forecast:

Morning Sky

In yesterday’s article, we looked at celestial markers that indicate the season is changing.  At this season, Arcturus is very low in the west-northwest.  The star is the brightest visible in the northern half of the sky, north of the celestial equator.  The sky’s imaginary equator is above Earth’s equator, and divides the sky into the northern half and southern half.  From the mid-northern latitudes, only part of the sky’s southern region is visible.  Sirius, the night’s brightest star, is visible across the planet and lies south of the celestial equator.  It is the night’s brightest star.  Canopus, the second brightest star is nearly 40° south of Sirius.  It is visible from America’s southern tier of states, but not from Chicago and northward.

This morning bright Jupiter is nearly 20° above the eastern horizon.  It is becoming easier to see each morning, rising about four minutes earlier each day.  Use a binocular to see up to four of its larger moons.  Through a telescope, the planet’s weather system is visible as a series of stripes across the planet.

Saturn, not as bright as Jupiter, is over 30° above the south-southeast horizon.  It is above the star Fomalhaut that is about halfway from the horizon to Saturn.

Mercury is retreating from the morning sky and into bright sunlight.  It rises fifty-two minutes before daybreak and is lost in sunlight when it is high enough to be seen.

Evening Sky

Other celestial markers in the evening sky indicate the seasonal shift. Antares, the heart of the Scorpion, is about 30° above the south-southeast horizon at one hour after sundown.  With the Summer Triangle in the eastern sky, topaz Arcturus is high in the south.

In the western sky Leo, with its brightest star, Regulus, is tipped toward the horizon, above brilliant Venus and Mars.  The two planets are in front of Cancer’s dimmer stars.

Venus continues to brighten.  Simply described, it is “that bright star” in the western sky after sunset.  An hour after nightfall, the planet is about 20° up in the west and over 18° to the lower right of Regulus.

Venus reaches an interval of maximum brightness on the 29^th.  While the planet is the third brightest regular celestial object, after the sun and moon, it varies in brightness. The change is visible across several months.

Venus is overtaking dimmer Mars, 5.1° to the upper left.  The rate at which the gap closes is slowing and Venus ends the chase on the 29^th when the gap closes to 3.6°, a quasi-conjunction.  Venus makes it to within 5° of separation, but it does not pass Mars.

Mars marches away from Venus, passing Regulus on July 10^th.  Venus’ eastward motion stalls July 16^th, leaving a 3.5° gap with Regulus. Venus finally passes the star on October 10^th in the morning sky.

Venus and Mars are close enough to fit into the same binocular field of view.  The better view is Venus with the Beehive star cluster.  Hold the binocular so that the planet is off center toward the upper left of the field.  The star cluster is to the lower right.

Watch the planets move toward Leo in the evening sky.

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