Stars are classified into spectral classes, of which there are seven basic classes and several more esoteric ones. The seven basics are O, B, A, F, G, K and M and they are shown here along with a few others:
The other classes show are C for Carbon stars (very old stars that are burning out), S (late type giants) and W which are the most interesting of them all, Wolf-Rayet which are massive stars with howling solar winds. If I do absolutely nothing else with spectroscopy it has been a huge success in teaching me more about stars and the wild variety of them out in the universe.
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My first foray into spectroscopy was barely a month ago and already I am shifting gears. It turns out it is pretty straight forward to image the spectra of stars, but processing it and making something of the image is another story entirely.
Like a lot of people I would imagine, I started using a program called Vspec, mainly because it was free and also because there are a lot of people using it. The problem I ran into rather quickly was that if you are starting from scratch and understand nothing about the spectrum, the software or the entire theory of spectroscopy then Vspec can be a bear to figure out.
So I broke down and ordered Rspec from the same guy I bought the Star Analyser 100 from and man did that make my life easier. In just a few days I went from things I knew were wrong but had no idea how to fix to this:
Which not only am I fairly sure has some semblance of being correct, but I actually understand some of! Interesting things about this profile include the 5850-5900 range showing sodium and calcium absorption lines, 5160-5180 showing a large concentration of magnesium lines, lines just before and just after 5400 showing iron and the dark lines just before 4300 showing CH or methane.
Now admittedly I looked up the spectrum in a reference book and got the information for the spectral lines from that book, but the cool part about it is I could actually see what they were talking about and their observations matched my images and curves. So either I am getting more correct in my image taking and processing, or more delusional in my old age, either of which works for me 🙂
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Stellar spectroscopy is a really interesting field, and since I have never been content on doing one thing and always being fascinated by things I don’t understand I decided to look into it. Stellar spectroscopy is the study of the spectrum of light being emitted or reflected by an object in space. This can tell you a lot of things, for example what the chemical makeup of a star is (which tells you the star type), or the speed at which an object is moving towards or away from you. My primary reason for wanting to look into this is to learn more about the stars themselves instead of just imaging them. In my mind spectroscopy and stars seem to naturally go together. To this end I ordered a Star Analyser 100 from Rspec Astro, great guy to deal with, you can visit his website at http://www.rspec-astro.com. Once I received the grating filter I have to try and figure out how to use it, so I made an exposure chart to see what the spectral lines (or stellar lines) look like. This is the stellar spectra of Arcturus:
Stellar Spectroscopy and star types
There are many different types of stars. Each star type or stellar classification can be determined through spectral analysis. As light passes through the filter a specific pattern of light emerges, including bands of darkness called absorption lines. Reading these patterns and comparing them to the known star types allows someone to identify the type of an unknown star.
All the different types of stars fit into seven basic classifications of typical stars, and a few more for stranger types which we believe are far less common. As I learn more about stars I plan on being able to come to my on conclusion about what type of a star my target is, and then compare it to what the real scientists say. Hopefully I will be able to match my results with theirs. Even if I don’t start off that way, it should be a lot of fun learning stellar spectroscopy!
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