Astronomy: The Sun and Stars

Earth's Revolution and the Night Sky

• As Earth revolves around the Sun, Polaris remains fixed in the northern sky.
• Certain stars near Polaris remain constant throughout the year, while different stars are visible in the southern sky.

Sun's Daily and Annual Motion

• Over the course of a day, the Sun appears nearly stationary compared to stars.
• The Sun's position changes throughout the year, tracing a path on the celestial sphere.
• It rises and sets daily, reaching its highest point in the sky at noon.

Ecliptic Path

• The ecliptic is the apparent annual path of the Sun across the celestial sphere.

Locating Polaris

• Polaris can be located using both terrestrial and celestial coordinates.
• Terrestrial coordinates:
  • Horizon is 0°, Zenith is 90°.
  • North: 0°/360°, East: 90°, South: 180°, West: 270°.

Altitude and Azimuth in Local Sky

• At the North Pole, the altitude of Polaris is 90°; at the Equator, it is 0°.
• The altitude of Polaris varies with latitude.

Celestial Equatorial Coordinates

• The Celestial Equator is at 0°, while the Celestial North Pole is at +90° and the South Pole at -90°.
• Right Ascension of Polaris: 02h 31m.
• Declination of Polaris: +89°.

Significant Dates

• Vernal Equinox: 0h or 24h.
• Autumnal Equinox: 12h.