Summer Triangle Corner: Deneb

Per NASA Science, the constellation Cygnus the swan hosts both visible and invisible treasures for Northern Hemisphere observers. Locate the brightest star, Deneb, which marks one corner of the Summer Triangle, then find Albireo at the swan's center. Through binoculars, an open cluster of young stars called Messier 29 comes into view; a telescope reveals Albireo as a jewel-like double star pairing a gold star with a brilliant blue one. The Cygnus Loop, a faint ring of gas from a supernova—the explosive remains of a massive dead star—also awaits those with optical aid. But the constellation's deepest wonder is Cygnus X-1, an invisible X-ray source detected only by NASA's Chandra Observatory. Discovered in 1971, it was the first X-ray source widely accepted as a black hole—a stellar remnant with the mass of about twenty Suns, spinning at over eight hundred times per second while devouring a nearby companion star. Some six thousand and seventy light-years distant, it poses no threat but offers a profound window into the most extreme objects in the universe.

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