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Today, I want to post a bit about . It's bit beyond pretty space picture, but a lot more useful as a scientific endeavor!

When the light of a star is decomposed into its using something called a grating, it's like seeing the rainbow after the rain. The star in that case is the sun, the rain droplets are the object decomposing its light, and the rainbow its the spectrum of the sun!

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Now, when scientists saw the of starlight, they noticed that the "rainbow" wasn't exactly continuous and smooth, but had some black lines in it. This lines, called lines, are caused by specific elements in the atmosphere of the star, blocking that specific . These lines are very specific to each star type, so they are like the bar codes in the items on a supermarket.

The nice thing about this is that if you examine these lines closely and correlate them with each star type, you could in theory determine the type of an unknown star. Why knowing the star type important, for starters, the star type in general determines how hot the star is and its color! Hotter stars are bluer in color, and "cooler" stars are redder.

Ok, now let's put the theory aside, and see what a bored amateur astronomer can do. Using a diffraction grating and my scope/camera, I took this image of a star named , the brightest star in the Corona Borealis. It shows the star itself (on the left) and its spectrum (on the right). This is a black and white camera, so the "rainbow" in in grayscale :/ (this is on purpose, since b/w cameras are more sensitive than color ones).

Did you see the small lines in the spectrum to the right? Those are absorption lines (they are called lines, a set of absorption lines caused by interaction of the starlight with atoms in its atmosphere)! When properly plotted, these absorption lines are shown as "dips" in the spectrum curve below. The exact location and how "deep" these dips are, and the overall shape of the curve help me determine which star type is.

If we compare the absorption lines in our spectrum to the absorption lines of the known star types, it can be seen that our star is a "Class A" star, a "white to blue white" star. In this star class, lines are the most prominent, so they can easily identified.

Plotting the same spectrum in a different way, the absorption lines can be easily be seen, and some other features are more apparent than before. See the wider dips to the right of the black curve? They are caused not by atoms on the star's atmosphere, but by Earth's own! The light of , travelling some 75 light years or so to reach us, is blocked at some wavelengths by the oxygen and water molecules in our atmosphere.

Well, I'll stop this here. This is just a glimpse of all the sorts of information that can be obtained by looking at the spectrum of light, in this case, . In fact, accounts for the vast majority of all the information we know about the universe, is that powerful. More importantly still, is within reach of the amateur community.

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