What is the angular distance measured eastward along the celestial equator from the vernal equinox called?

The angular distance measured eastward along the celestial equator from the vernal equinox is referred to as Right Ascension. This term is an essential concept in celestial navigation and astronomy, as it helps in locating stars and other celestial objects in the sky.

Right Ascension is measured in hours, minutes, and seconds, with one hour corresponding to 15 degrees of arc. It is analogous to longitude on Earth but is specifically employed in the celestial sphere context. The vernal equinox serves as the starting point (0 hours of right ascension), which makes it a fundamental reference point in the celestial coordinate system.

Understanding right ascension is crucial for astronomers when mapping out the positions of celestial bodies, as it allows them to specify the location of any given star or celestial object relative to this coordinate system. Other terms like declination, zenith, and altitude refer to different measurements or locations in the sky and are not used to describe the angular distance from the vernal equinox along the celestial equator.