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Knowledge of the location of Earth has been shaped by 400 years of telescopic observations, and has expanded radically since the start of the 20th century. Initially, Earth was believed to be the center of the Universe , which consisted only of those planets visible with the naked eye and an outlying sphere of fixed stars . [ 1 ]
Ignoring the influence of other Solar System bodies, Earth's orbit, also called Earth's revolution, is an ellipse with the Earth–Sun barycenter as one focus with a current eccentricity of 0.0167. Since this value is close to zero, the center of the orbit is relatively close to the center of the Sun (relative to the size of the orbit).
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Trying to illustrate two conflicting ideas in a drawing presented as representing one of those two ideas is counter-productive to the use of a drawing to help clarify the point. I would add that it’s not clear to say that “The ecliptic is the apparent path of the Sun on the celestial sphere.”
The spokes of that "star" are marked with constellation abbreviations, "Cas" for "Cassiopeia", etc. The spiral arms are colored differently in order to highlight what structure belongs to which arm. H II regions are marked as dots colored in the same color as their spiral arm. They come in three sizes, measured by the excitation parameter U:
The Earth's radius is the distance from Earth's center to its surface, about 6,371 km (3,959 mi). While "radius" normally is a characteristic of perfect spheres, the Earth deviates from spherical by only a third of a percent, sufficiently close to treat it as a sphere in many contexts and justifying the term "the radius of the Earth".
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The rotational axis of Earth, for example, is the imaginary line that passes through both the North Pole and South Pole, whereas the Earth's orbital axis is the line perpendicular to the imaginary plane through which the Earth moves as it revolves around the Sun; the Earth's obliquity or axial tilt is the angle between these two lines.