Astrology has been always commonly associated with astronomy, but they are actually not related with each other. The latter is a field of science but the former is not.
According to dictionary;
Astrology is the study of planets and human behavior: the study of the positions of the Moon, other planets and stars in the belief that their motions or movements affect human beings.
Astronomy is the scientific study of universe, especially of the motions, positions, sizes, composition, and behavior of heavenly bodies. These bodies are studied and interpreted from the radiation they emit and from data gathered by interplanetary probes.
Recently, the addition of the 13th zodiac sign causes discomfort to astrology believers. Let’s try to look into the science aspect of the issue.
There are actually 88 constellations (star patterns or group of stars in a definite area of the sky) identified officially, most of which were named in the ancient times. Most of these had been recorded by Babylonian astronomers before 2000 BC. In 150 AD, Ptolemy, a Greek astronomer, described 48 star patterns, including the famous ones like Ursa Major (the Great Bear).
To an observer on Earth, the stars appear to be attached to the inside of a vast hollow globe which spins around the Earth from East to West once a day. Although this is not true, (since the Earth, and not the sky, is the one spinning) it is often useful for astronomers to pretend that this globe in the sky really does exist. This is called as the “celestial sphere” which is of great help to astronomers to plot the position of stars in the sky. During a year, the sun appears to take a particular path through this celestial sphere. This path marks the center of the band of sky known as the Zodiac. There are 12 divisions of the zodiac, each of one represented by a constellation. The Sun seems to stay for about a month in each constellation.
The addition of the 13th zodiac was proposed as early as 1930. Based on the 1930 IAU constellation boundaries, suggestions that "there are really 13 astrological signs" because "the Sun is in the sign of Ophiuchus" between November 29 and December 17 have been published since at least the 1970s. In 1970, Stephen Schmidt in his Astrology 14 advocated a 14-sign zodiac, introducing Ophiuchus (December 6 to December 31) and Cetus (May 12 to June 6) as new signs. The idea was taken up by Walter Berg in his The 13 Signs of the Zodiac (1995), a suggestion that achieved some popularity in Japan (where Ophiuchus is known as snake messenger).
The following are the "real" dates of astrological signs according to astronomers;
Capricorn: Jan. 20-Feb. 16.
Aquarius: Feb. 16-March 11.
Pisces: March 11-April 18.
Aries: April 18-May 13.
Taurus: May 13-June 21.
Gemini: June 21-July 20.
Cancer: July 20-Aug. 10.
Leo: Aug. 10-Sept. 16.
Virgo: Sept. 16-Oct. 30.
Libra: Oct. 30-Nov. 23.
Scorpio: Nov. 23-29.
Ophiuchus: Nov. 29-Dec. 17.
Sagittarius: Dec. 17-Jan. 20.
Capricorn: Jan. 20-Feb. 16.
Aquarius: Feb. 16-March 11.
Pisces: March 11-April 18.
Aries: April 18-May 13.
Taurus: May 13-June 21.
Gemini: June 21-July 20.
Cancer: July 20-Aug. 10.
Leo: Aug. 10-Sept. 16.
Virgo: Sept. 16-Oct. 30.
Libra: Oct. 30-Nov. 23.
Scorpio: Nov. 23-29.
Ophiuchus: Nov. 29-Dec. 17.
Sagittarius: Dec. 17-Jan. 20.
On my personal perspective, we have nothing to worry about this thing. I believe that most of us, even astrologers themselves believe that human behaviour or fate is not dependent to the motions of these celestial bodies. We are the one making our own course; it is a God-given gift to all of us to have freewill. So don’t over react… it doesn’t changes anything.
Sources:
Microsoft® Encarta® 2009. © 1993-2008 Microsoft Corporation. All rights reserved.
Muirden, J (1993). Visual Factfinder Stars and Planets.
LiveScience.com
Wikipedia.com
starryskies.com (Image Source)
starryskies.com (Image Source)