Astronomers who want to understand stars face one giant obstacle: the stars are far away. Very far away. Really, really, far away. In the words of Douglas Adams,
Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space.
If a geologist wants to analyze a new mineral, he can simply travel to the outcrop, dig out a sample or two, and bring it back to his lab. But we astronomers don't have this option; we can't ever (well, not in my lifetime) gather material from a star. All we can do is ... look.
And, of course, we don't get a choice about the point of view. Some regions of space are full of giant clouds of gas and dust, which can block optical light completely. If a particularly interesting object just happens to lie behind a big cloud of dust, that's just too bad.
There's the Earth's own atmosphere, too, which blocks most of the electromagnetic radiation from space (which isn't all bad -- X-ray and ultraviolet rays can be nasty, as a day on the beach can reveal). The tiny fraction of waves which can pass through clear air often run into clouds or rain, especially here in Rochester.
Oh, and the Sun. It's a real pain: more than half of all the hours are ruined by its glare. The only time it really gets dark is when normal people need to sleep.
Yet somehow, despite all these obstacles, astronomers over the past few hundred years have found ways to measure many properties of stars:
We even believe we understand the broad outlines of stellar evolution, despite the fact that the typical timescales are thousands to billions of years.
How have astronomers managed to learn so much about such distant objects? That's what this course will try to explain.
Copyright © Michael Richmond. This work is licensed under a Creative Commons License.