February 11, 2023: Daylight is longer than darkness today until Halloween. Venus is moving toward Jupiter in the west-southwest, while Mars marches eastward against Taurus.
by Jeffrey L. Hunt
Chicago, Illinois: Sunrise, 6:52 a.m. CST; Sunset, 5:19 p.m. CST. Check local sources for sunrise and sunset times for your location. Times are calculated from the U.S. Naval Observatory’s MICA computer program.
Jupiter’s Great Red Spot’s transit times, when it is in the center of the planet in the southern hemisphere: 9:28 UT, 19:24 UT; Feb 12, 5:20 UT. Convert the time to your time zone. In the US, subtract five hours for EST, six hours for CST, and so on. Use a telescope to see the spot. Times are from Sky & Telescope magazine.
Today daylight is longer than darkness. This statement is not about the upcoming equinox when daylight and nighttime are nearly equal. Let’s distinguish some terminology. When the sun is in the sky that’s daytime. When it is not, that’s nighttime.
Nighttime can be divided into twilight – both evening and morning – and darkness, when the sky is as dark as it gets naturally. This occurs when the sun is 18° below the horizon. Night occurs in three phases, evening twilight, darkness, and morning twilight.
On the chart above, calculated from US Naval Observatory data, three lines show daylight, darkness, and twilight – with morning twilight and evening twilight added together.
The red diamonds show today’s date, when daylight is longer than darkness. That’s 10 hours, 27 minutes compared to 10 hours, 24 minutes for darkness. The daylight curve increases somewhat through the equinox on March 20th, when daylight’s length is 12 hours, 9 minutes. Darkness is 8 hours, 45 minutes.
At the summer solstice, daylight lasts 15 hours, 13 minutes. Darkness decreases to 4 hours, 23 minutes. Interestingly, twilight is a minute or two longer than darkness from June 17th through June 26th.
After the solstice, daylight begins to decrease and darkness lengthens. By the equinox, September 23, the sun is above the horizon for 12 hours, 8 minutes and darkness increases to 8 hours, 45 minutes.
On Halloween, daylight is four minutes shorter than darkness and shorter daylight continues for over 100 days at Chicago’s latitude. Daylight continues to shrink until the solstice on December 21 with 9 hours, 8 minutes of sunlight.
The dates that this occurs varies with latitude. Locales farther southward, suffer with shorter periods when darkness is longer than sunlight. Farther northward, the interval is longer.
In Miami, Florida, daylight became longer on January 11th; in Tucson, January 30th. From Seattle, Washington, the interval ends in four days, but Juneau, Alaska does not reach this state until March 21st, 120 days when darkness is longer than daylight.
Juneau, though, experiences a phase of no darkness from April 27th through August 15th. It has daylight and twilight that does not phase to darkness.
Here is today’s planet forecast:
Morning Sky
The gibbous moon, 72% illuminated, is about one-third of the way up in the sky in the south-southwest, and 3.1° to the upper left of Spica, the brightest star in Virgo. The lunar orb continues its eastward journey, passing through the half-full, Last Quarter phase, on the 13th.
Mercury continues its morning plunge into bright sunlight. Rising one hour before sunup, the planet is only 4° and in the glare of the approaching dawn.
Evening Sky
Saturn, setting only fifteen minutes after sunset, is closer to the sun in the sky than Mercury. The Ringed wonder is at conjunction on the far arc of its solar orbit in five days.
At forty-five minutes after sundown, Venus sparkles brilliantly from the west-southwestern sky. It is about 15° above the horizon at 45 minutes after sunset. Its brilliance competes with lights on low-flying airplanes or mistaken for something out of this world.
Bright Jupiter is higher in the sky and 18.5° to the upper left of Venus. The Jovian Giant is moving slowly through Cetus. Venus moves quicker eastward and overtakes Jupiter on March 1st in a spectacular conjunction. A Venus-Jupiter conjunction during twilight is a striking event.
The best night is March 1st, but from February 20th through March 11th, Venus is within 10° of Jupiter. The two brightest starlike bodies stand near each other.
Ten degrees is about the distance from your thumb to pinky finger on your fist when extended to arm’s length. Close one eye and sight across your fist to note the distance. Similarly, the sun’s final arc to sunset each day is about 15°. Your finger nail on your pinky finger, when extended to arm’s length is about one-half degree. It covers the full moon or the sun. Try it.
At this hour, Mars is in the southeast, marching eastward with Taurus as the sidereal backdrop. In another 45 minutes, the background stars are easily visible behind the Red Planet.
Mars is 8.6° to the upper left of Aldebaran and 10.1° from Elnath, the Bull’s northern horn.
The gibbous moon rises after midnight tomorrow morning.
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