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Deneb — the brightest star of Cygnus, the swan — stands high in the eastern sky during the evenings at this time of year. It forms the northernmost point of the big, bright Summer Triangle, so it’s easy to pick out.
Deneb’s brilliance makes it a popular target for casual skywatchers, but not necessarily for the pros.
They already know some basics about Deneb: It’s a blue supergiant that’s perhaps 2500 light-years away, for example. And it’s going through some changes. They should cause the star to get even bigger, and to change colors from blue to orange. But a lot of questions remain.
It’s hard to get answers because there just isn’t a lot of time available to study an individual star.
Most of the observing time on the world’s biggest telescopes is devoted to objects that are faint and far away — things like distant galaxies and quasars.
And when astronomers do look at a bright star, it’s often as part of a study of a group of similar objects — blue supergiants, for example, or stars that pulse in the same way that Deneb does.
To study a star in detail, astronomers tend to use smaller telescopes. A study about Deneb a few years ago, for example, used more than 300 nights of observations made with a one-meter telescope, which is pretty small by modern standards.
Studies like these have answered some of the questions about Deneb. But as is often the case, they’ve raised a lot more — questions that may take some time to answer.