If the twelve constellations of Tiangong are regarded as a circle, what star or constellation is its center?

The zodiac signs are arranged along the ecliptic, and the intersection angle between the ecliptic and the celestial equator is 23 degrees and 26 minutes (the intersection angle between the ecliptic and the celestial equator); The two intersections of the ecliptic and the celestial equator are the vernal equinox and the autumnal equinox. In the ecliptic coordinate system, the longitude of celestial bodies is measured eastward along the ecliptic from the vernal equinox, with positive north latitude and negative south latitude. The distance between the south and north poles and the corresponding celestial pole is 23 degrees and 26 minutes. Because the earth's revolution is perturbed by the moon and other planets, the orbit of the earth's revolution is not a strict plane, that is, it produces irregular continuous changes in space, which includes many short-term and a slow long-term movements. Short-period motion can be averagely eliminated in a certain time, and the orbital plane with periodic motion eliminated is called instantaneous average orbital plane. The strict definition of the ecliptic is: the great circle where the instantaneous average orbital plane of the center of mass of the Earth-Moon system revolves around the sun and intersects the celestial sphere. The ecliptic is the base circle of the ecliptic coordinate system on the celestial sphere. The ecliptic is the apparent path of the sun on the celestial sphere in a year. It seems that the path of its movement between stars is obviously the path that the planet passes through every year. More specifically, it is the intersection of a sphere (celestial sphere) and the ecliptic plane; Geometrically, it is the average orbital plane containing the earth's orbit around the sun. The ecliptic plane should be a stable ecliptic plane, which is perpendicular to the sum of angular momentum of all planetary orbital planes, and Jupiter should be the most influential. The current ecliptic plane is inclined about 65438 0.5 relative to the constant ecliptic. In fact, it can be simply understood as the plane of the earth's rotation, and the above 12 constellation is called the zodiac 12 constellation, which is more vividly understood. The western word "ecliptic" extends from the place where the solar eclipse occurred. Because the earth's revolution is perturbed by the moon and other planets, the orbit of the earth's revolution is not a strict plane, that is, it produces irregular continuous changes in space, which includes many short-term and a slow long-term movements. Short-period motion can be averagely eliminated in a certain time, and the orbital plane with periodic motion eliminated is called instantaneous average orbital plane. The strict definition of the ecliptic is: the great circle where the instantaneous average orbital plane of the center of mass of the Earth-Moon system revolves around the sun and intersects the celestial sphere. The ecliptic is the base circle of the ecliptic coordinate system on the celestial sphere. The apparent motion of the sun on the celestial sphere can be divided into two situations, namely, Sunday apparent motion and annual apparent motion. "Sunday visual movement" is a phenomenon that the sun rises and sets every day, which is essentially a visual effect caused by the rotation of the earth. "Annual apparent motion" refers to the phenomenon that the earth's revolution causes the sun to "cross" between constellations. Astronomy calls the annual apparent trajectory of the sun on the earth, that is, the great circle of the apparent path of the sun in the sky "ecliptic", that is, the projection of the orbital plane of the earth on the earth. The sun rotates once a year on the earth along the ecliptic. In order to locate the ecliptic conveniently, people divide it into twelve equal parts (each equal to 30), and each part is named after an adjacent constellation. These constellations are called the zodiac or the zodiac. This is equivalent to dividing a year into twelve segments, in which the sun enters a constellation. In the west, when a person is born, which constellation the sun is going to, he is said to belong to this constellation. If you were born in that constellation, you just couldn't see your constellation in the month when you were born. Because the constellation you belong to at this time is just on the back of the connection between the earth and the sun. The earliest historical records about the ecliptic appeared in Babylonian culture. They use the position of the sun on the ecliptic to determine the date. The earliest function of the zodiac is like the twelve months in today's calendar. Aries is regarded as the beginning of the year from the vernal equinox, and the day when the sun moves to Libra is equally divided between day and night. [Edit this paragraph] The zodiac was first used by astronomers in Babylon in the 5th century BC. Imagine the whole sky as a big ball, and the stars are all distributed on the spherical shell. This is the so-called celestial sphere. The ecliptic is the trajectory of the sun on the celestial sphere. 8 degrees on each side of the ecliptic is the ecliptic. Planets all move on the ecliptic. Babylonians also divided the zodiac into twelve regions, but the names of these regions came from the ancient Greeks. In fact, the names of most constellations come from Greek mythology. The word zodiac comes from the Greek zodiakos, which means zoo. In the eyes of the Greeks, constellations are made up of various animals, which is the origin of the names of the twelve constellations. In astronomy, the orbit of the sun around the earth with the earth as the center is called the ecliptic. The width of the ecliptic is 16 degrees, and it is 360 degrees around the earth. The ecliptic plane includes the orbits of all planets except Pluto, including constellations. Every 30 degrees, there is a constellation in each range, with a total of 12 constellations, which is called "Zodiac". The sun runs from west to east on the ecliptic and circles the sky once a year. There are twelve constellations on a belt on both sides of the ecliptic. They are Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius and Pisces. People on earth can see them one after another in a year. Babylonians observed these constellations for a long time, determined the ecliptic through observation, and divided the ecliptic into 12 equal parts, each equal part was 30 degrees, which was called 1 segment. The sun travels around the ecliptic in 12 months/cycle, so it travels on the ecliptic every month 1 segment. In the eyes of the ancients, the sun was Apollo, and its resting place must be a magnificent palace. Therefore, they called the 1 section of the ecliptic 1 palace. In this way, the section 12 on the ecliptic becomes the "zodiac". The names of the zodiac signs are similar to the 12 constellation near the zodiac signs, namely Aries, Taurus, Twin Uterus, Cancer, Lion, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius and Pisces. Although the names of the zodiac signs are the same as those of the 12 constellation near the zodiac signs, they are essentially different. The zodiac indicates the position of the sun on the ecliptic, and the size of each constellation is fixed. It's all 30 degrees, and the time when the sun enters each house is basically fixed. Now the sun comes to the vernal equinox on March 2 1 every year and enters Aries Palace. Around June 22, I came to the summer solstice and entered the Cancer Palace. On September 2 1 day, I came to the autumnal equinox and entered Tianping Palace. 65438+came to the winter solstice around February 22 and entered Capricorn Palace. On my birthday, the sun just passed by my house, so I couldn't see my horoscope on my birthday. However, this was not the case before 2000, because under the gravity of the sun and the moon, the rotation axis of the earth did not point to the same position in the sky, but turned around in the sky. This phenomenon is called precession. Due to precession, before 2000, the sun was located in the above four positions of Aries, Cancer, Libra and Capricorn. Different from the ecliptic, the 12 constellation near the ecliptic has different sizes. For example, the width of Pisces is 49 degrees, while the width of Cancer is only 2 1 degree. 12 constellation is not necessarily located on the ecliptic, but distributed within 8 degrees on both sides of the ecliptic.