The night sky, when viewed from a dark rural location on a clear evening, is a spectacle of stars. Some of these stars shine with quite brightly, forming familiar constellations such as Orion the Hunter, or creating distinctive shapes like the Summer Triangle. Other stars shine far less brightly. The individual brightness of a star is determined by a combination of how much light it creates and its distance from Earth. These two fundamental characteristics result in varying levels of brightness among the stars we observe. To quantify and describe the brightness of stars, astronomers use the concept of magnitude. Magnitude and its Logarithmic Scale The magnitude of an astronomical object refers to its apparent brightness as observed from Earth. Historically, the ancient Greeks called the brightest stars first-magnitude stars, with the dimmest visible stars described as sixth-magnitude stars. Magnitudes 2, 3, 4, and 5 fell in between. The key takeaway from this early classification is th...
