What is the red line on the globe?

The red line on the earth is the ecliptic line.

The ecliptic is the earth's orbit around the sun. Because the earth goes around the sun only once a year and returns to its original position. The route that the sun "walks" in this way is called the ecliptic.

Moreover, the orbit of the moon around the earth, that is, the "white road", and the orbits of the planets around the sun are very close to the ecliptic. It is a great circle assumed by the celestial sphere, that is, the projection of the earth's orbit on the celestial sphere. The ecliptic intersects the equatorial plane in vernal equinox and vernal equinox.

Because the earth's rotation axis is not perpendicular to the revolution plane, the equatorial plane of the celestial sphere and the ecliptic plane do not coincide, and the included angle between the two planes is 23 26' 21. (measured in AD 2000), the intersection of two planes connects the vernal equinox and the autumnal equinox.

When the earth looks down and the sun changes from south to north, it is called the vernal equinox. A circle from this field to the east, from 0 to 360, is the meridian of the ecliptic, and the angle is called the longitude of the ecliptic. The latitude of the ecliptic is 90 degrees north latitude and 90 degrees south latitude.

Seen from the center of the earth, the ecliptic is very close to the apparent annual trajectory of the sun in the star. Only by using precise astronomical instruments can we detect the difference between the ecliptic and the apparent annual path of the sun. The ecliptic is the base circle of the ecliptic coordinate system on the celestial sphere.

Extended data:

The relationship between the ecliptic and the equator

Because the rotation axis of the earth is not perpendicular to the orbital plane, and the equatorial plane is not parallel to the ecliptic, it has an included angle of 23 26', which is called the ecliptic angle.

The great circles formed by the intersection of the equatorial plane and the ecliptic plane with the earth are called the equator and the ecliptic respectively. The intersection of these two planes is just at the two ends of a diameter line of the earth, which is the famous bisector (vernal equinox and bisector).

The bisector of the sun passing from south to north is called the first point of vernal equinox or Aries, and the longitude of the ecliptic is usually marked with the letter λ, starting from 0 to 360.

The latitude of the ecliptic is usually expressed by the letter β, which is based on the ecliptic, ranging from 0 to 90 north latitude and 0 to-90 south latitude. The vernal equinox is also defined as the origin of equatorial coordinates, and the right ascension is also measured from 0 to 24, usually expressed by the letter α or R.A. ..

The declination is represented by the letters δ or Del. It ranges from 0 to 90 degrees north and 0 to -90 degrees south from the equatorial plane. Simple rotation mode can convert α, δ sum into λ, β.

Second, astronomical phenomena

1, Zodiac killer

Around the 5th century BC, Babylonian astronomers first used the concept of the zodiac. 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.

2. Zodiac plane

The ecliptic plane is the plane of the earth's orbit. Because the gravity of the moon and other planets affects the revolution of the earth, the position of the ecliptic plane in space is always changing irregularly.

But in change, this plane always passes through the center of the sun at any time. The great circle where the ecliptic plane intersects the celestial sphere is called the ecliptic.

References:

Baidu Encyclopedia-Global

Baidu encyclopedia-ecliptic