But the Sun is surrounded by a dilute hot gas called the corona with a much hotter temperature of around 2 million degrees. From Kirchoff's laws, the hot and dilute or thin coronal gas against the cooler photospheric background should yield an emission line spectrum. The photosphere gives an absorption line spectrum. Explain how the width of an absorption line can tell us the temperature of the gas in the Sun. The absorption line is broadened via the Doppler effect by the thermal motion of the atoms.
Hotter gas leads to broader lines.
The Earth orbits in a nearly circular path around the Sun. The Earth would move in a straight line with direction tangent to its orbit, and it would move at constant speed. This follows from Newton's 1st law. The tilt of the Earth's axis to the ecliptic is about 23.5 degrees. We would still have four seasons, but they would tend to be more extreme.