March 20, 2023: The Vernal equinox occurs today at 4:24 p.m. CDT. The sun’s rays are most direct on Earth’s equator. Venus, Jupiter, and Mars are visible after sundown.
by Jeffrey L. Hunt
Chicago, Illinois: Sunrise, 6:54 a.m. CDT; Sunset, 7:03 p.m. CDT. Check local sources for sunrise and sunset times for your location. Times are calculated from the U.S. Naval Observatory’s MICA computer program.
Daylight’s length is 12 hours, nine minutes today. The Vernal equinox occurs today at 4:24 p.m. CDT. The equinox is an event and a place in the sky.
The sky has several coordinate systems. One is based on the celestial equator, an imaginary circle around the sky above Earth’s imaginary equator. The celestial equator references Earth’s rotation, with Polaris, the North Star, near the rotational axis. Another is framed on the plane of the solar system, known as the ecliptic. This is where the sun, moon, and planets appear to move. This is the system used most for the planet forecasts made in these articles. Another uses the plane of the Milky Way for reference.
The ecliptic is inclined 23.5° compared to the celestial equator and they cross at two points, the Vernal equinox and Autumnal equinox. The Vernal equinox is the origin of the equatorial and ecliptic systems. The Autumnal equinox is halfway around the sky, 180° from the Vernal point.
When the sun is at the Vernal equinox point, the sun is on the celestial equator, rising in the east and setting in the west. Without the effects of Earth’s atmosphere and the definitions for sunrise and sunset, daylight would be 12 hours.
The sun seems to move along the ecliptic because of Earth’s revolution around the sun. The sun’s changing sunrise place, noon point, and sunset location are from our planet’s tilt.
Today, the sun’s coordinates are at the origin point of two celestial systems, signaling the beginning of the spring season in the northern hemisphere. The sun’s rays are most direct at the equator the solar concentration continues into September. Happy Spring!
Here is today’s planet forecast:
Morning Sky
Saturn is nearly ready to appear in the east-southeast before sunrise. At 30 minutes before sunrise, it is nearly 5° above the horizon. When the planet is higher in the sky and in a darker sky, it is easier to see.
Meanwhile, thirty minutes earlier, the Summer Triangle – Vega, Altair, and Deneb – is in the eastern sky. Each star belongs to its own constellation. The season name for the large triangle is because the shape makes its first appearance in the eastern evening sky at about the summer solstice.
Vega is the third brightest star visible from mid-northern latitudes. Shining from a distance of about 25 lights, this blue-white star is nearly 50 times brighter than the sun. Altair, part of Aquila the Eagle, is nearly 17 light years away and is over 10 times brighter than the sun. In comparison, Deneb is one of the brightest stars in our region of the Milky Way. It is over 1,400 light years away and shines with an intensity of 48,000 suns, making it the 14th brightest star for our northern hemisphere sky watchers.
Deneb is the tail of Cygnus the Swan. It flies southward along the plane of the Milky Way toward the southern constellations Sagittarius and Scorpius. Albireo marks the head of the bird. The star is about halfway from Vega to Altair, to the inside of the triangle.
Albireo is a magnificent sight through a telescope where it separates into two stars, one golden and the other sapphire. They revolve around a common center of mass in over 100 years.
Evening Sky
Mercury is rapidly climbing into the evening sky, setting 15 minutes after the sun this evening. The time interval increases five to six minutes each evening. Mercury is bright, but not high enough, yet, to see.
Venus continues to widen a gap to Jupiter in the western sky at 45 minutes after sundown. Setting nearly three hours after the sun, Venus is nearly 25° above the horizon at this hour. Venus steps eastward about 1° each evening, passing Hamal, the brightest star in Aries, in a wide conjunction in a few evenings.
Jupiter is over 5° above the horizon and 18.5° to the lower right of Venus. The Jovian Giant is bright, but unless there is a clear view of the western horizon, the planet is likely blocked by obstacles in the neighborhood. The planet continues its descent into bright evening twilight to reappear in the morning sky during May after its solar conjunction.
While Venus opens a gap to Jupiter, it closes a wide separation to Mars, nearly 53° to its upper left.
The Red Planet is high in the southwest, marching eastward in Taurus and near the Gemini border. It is east of the Bull’s horns, 5.9° to the upper left of Elnath and 5.2° from Zeta Tauri. Propus, in Gemini, is 6.6° to the upper left of Mars.
Through a binocular, Mars and Propus are nearly at opposite edges of the field of view, along with Messier 35 (M 35 on the chart), a star cluster with bright blue stars. The cluster can be seen in a dark sky without an optical assist. It is dimmer than the Pleiades star cluster because it is over four times farther away than the Seven Sisters.
Venus moves through this region of the sky during the second week of May as it cuts the gap to Mars.
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