Deneb, a Supergiant 200,000 Times Brighter Than the Sun
Alpha Cygni, better known as Deneb, is a first magnitude star, the nineteenth in order of brightness among those visible to the naked eye. Despite multiple studies over the decades, we still know relatively little about this very bright and distant supergiant
Even those who understand little about astronomy probably know the Summer Triangle, one of the easiest asterisms to detect from our hemisphere on summer nights as long as the sky is just a little dark. It is formed by three white stars: Vega, the most brilliant of the constellation of Lira, Altair, the brightest of the Eagle, and Deneb, Alpha Cygni, the brightest star of the Swan.
Of the three, the brightest is Vega, with a visual magnitude of 0.03. Follow Altair with 0.76, then Deneb with 1.25 (stellar magnitudes work in reverse: larger values indicate lower brightness). However, the difference between the three stars appears minimal to the human eye, so much so that it is easy to consider them as the vertices of an imaginary celestial triangle. Therefore, it would be reasonable to think that even their distances from Earth are approximately equal. The reasoning applies to Altair and Vega, which…
