Last night was cold, really cold.. When I got home from work this morning, it was a bitterly-cold -4 Fahrenheit. So, with last night being a prime example of a cold winter night, many people are asking a question: why do stars look brighter in winter, anyway?
See also: why are clear winter nights so doggone cold?
Well, the short answer is this: Earth faces more bright stars in winter than any other time of year. For a detailed explanation, continue reading.
To understand why we see different stars at night, one has to understand celestial mechanics. The Earth is a 360 degree sphere that turns on its axis once a day, meaning that, at any given time, stars are always up, albeit out-shown by the Sun during daylight hours. As the Earth travels around the Sun I its orbit, the direction that we face at night changes a little bit every day, which is why a given star will rise about 4 minutes earlier each night as the year progresses.
And there's more.
Earthy motion aside, there's the galaxy that plays a role, too. The Milky Way galaxy is a spiral galaxy. In practical terms, the Milky Way, if seen from the outside, would look somewhat like a giant, flat disc with a bulge in its center. The central region of the Milky Way is populated by a lot of old stars wile the outer regions are inhabited by young, bright blue stars.
As for the answer to our question of why stars look brighter in winter, the answer is simply this: stars look brighter because, during winter, we face toward the outside of the Milky way, which means that during winter, we are facing more of these young, bright, blue stars than at any other time of year: mystery solved.
As always, would-be sky watchers in the Cleveland area should be sure to keep an eye on the Cleveland weather forecast and, for hour-by-hour cloud predictions, the Cleveland Clear Sky Clock. Live somewhere else? Find a clock and see if it will be clear near you.
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