Astronomía - Esfera Celeste

Introduction to Celestial Sphere and Coordinate Systems

Overview of the Celestial Sphere

• The class introduces the concept of the celestial sphere, its elements, and commonly used coordinate systems for locating objects in the sky.

Earth Coordinates

• Location on Earth is determined using two coordinates: latitude (symbolized by 'φ') and longitude (symbolized by 'λ').

• Latitude is measured from parallels, with the equator as the fundamental parallel; longitude is measured from meridians, particularly the Greenwich Meridian.

Transitioning to Celestial Coordinates

• To observe celestial bodies, terrestrial coordinates must be translated onto the celestial sphere.

• The celestial sphere is represented as a circle centered on Earth, with observers at this center.

Key Points on Celestial Orientation

• Two critical points are defined:

• Zenith (Z): directly above an observer's head.

• Nadir (Z'): directly below their feet.

Axes and Cardinal Directions

• The vertical axis connects zenith and nadir while a horizontal axis intersects it at cardinal points North and South.

• This representation varies based on whether one is in the Northern or Southern Hemisphere.

Understanding Hemispheres and Horizon Plane

Division of Celestial Sphere

• The horizon plane divides the celestial sphere into two hemispheres:

• Visible Hemisphere: everything above the horizon including zenith.

• Invisible Hemisphere: everything below including nadir.

Horizontal Meridian Axis

• A horizontal meridian axis connects both celestial poles (North and South), extending from Earth's axis.

Importance of Observer's Position

• The position of North/South depends on an observer’s location; what appears "up" or "down" can differ based on hemisphere orientation.

Celestial Equator and Ecliptic Path

Defining Celestial Equator

• The celestial equator (Q') is perpendicular to Earth's axis, representing a projection of Earth's equator onto space.

Understanding Ecliptic Motion