What is the term for the 21 brightest stars observed from Earth?

The term for the 21 brightest stars observed from Earth is known as "magnitude stars." In astronomical terms, "magnitude" refers to the brightness of a star as seen from Earth. The brighter a star appears in the night sky, the lower its magnitude number is. The most famous group of the brightest stars are often cataloged and known collectively for their apparent brightness, which is why the concept of magnitude is essential in this context. This classification allows astronomers and stargazers to identify and refer to the brightest stars using a standardized system, enhancing our understanding of stellar brightness in our night sky.

The other terms listed do not relate to the brightness classification of stars. While elliptical stars may refer to types of galaxies, supernova stars describe a specific astronomical event involving the explosion of a star, and binary stars refer to systems where two stars orbit each other. Neither of these categories pertains to the classification of the brightest stars specifically observable from Earth.