Courtesy of EarthSky
A Clear Voice for Science
Visit EarthSky at
If you could see the stars during the daytime, you would see the sun shining in front of the constellation Ophiuchus today. At about this time each year, the sun passes out of Scorpius to enter Ophiuchus. Like Scorpius, Ophiuchus is a constellation of the Zodiac, and every year the sun passes in front of Ophiuchus from about November 30 until December 17.
The ecliptic – which translates on our sky’s dome as the sun’s annual path in front of the background stars – actually passes through 13 constellations, although this is not commonly known. After all, when you read the horoscope in the daily newspaper or a monthly magazine, you see only 12 constellations, or signs, mentioned. No one ever claims to be an “Ophiuchus.” There are the 12 traditional zodiacal constellations. Nevertheless, the sun passes through Ophiuchus as surely as it does the others.
Today’s constellation boundaries were drawn out by the International Astronomers Union in the 1930s.
Look at the chart carefully, and you will see that the border between Ophiuchus and the constellation Scorpius for the most part lies just south of, or below, the ecliptic. In ancient times, the Ophuichus/Scorpius border was likely placed to the north of, or above, the ecliptic. Had the International Astronomers Union done likewise, the sun’s annual passing in front of Scorpius would be from about November 23 till December 17, not November 23 to November 29.
Written by Bruce McClure