What is Arcturus?
Arcturus is the third brightest star in the night sky. It is located slightly less than 37 light-years away, in the constellation Boötes. The easiest way for an amateur astronomer to locate Arcturus is to follow the arc made by the handle of the Big Dipper. Arcturus is a red giant star with a mass between 1 and 1.5 times that of the Sun. It is notable for its particularly strong emission lines, meaning its atmosphere is dusty and low-temperature compared to that of a main sequence star. This is common among red giants, but particularly pronounced with Arcturus. Instead of having a clearly demarcated atmosphere like the Sun, the atmospheres of red giants such as Arcturus tends to just trail off into space. Although Arcturus is similar to the mass of the Sun, it is much larger, measuring about 16 solar diameters. Having departed the main sequence, it no longer burns hydrogen in its core, but rather in a shell outside of an inert helium core. This helium is the product of hundreds of mill
