I'm a science writer and editor. I work with clients in the observatory and planetarium community, as well as my own book, web, planetarium, and other projects.
Need a writer/editor? Visit my services page for my projects and availability.
Note: The ads you see below and at the bottom of this page are screened for content and many fine companies do appear here. Occasionally ads I don't want DO slip through, particularly for pseudo-science, st*r-naming, ID, and other questionable sites. Please understand that I cannot be held responsible for their content. Do visit them if you wish, but as with all advertising, be logical and use common sense.
In the last entry, I referred to a star that astronomers studied to understand its chemical makeup in an effort to figure out where it came from. That raised a question about how astronomers figure out the chemical makeup of a star.
They use a technique called spectroscopy. That's really a $25.00 word that means "breaking the light up into its wavelengths" and then comparing the data to the spectral fingerprints of known chemical elements. This is something that chemistry folks (who study the elements in the universe) do all the time, and a technique that let astronomers look at the radiation emitted from an object in space in new ways. It's fair to say that when astronomers began using spectroscopy to study stars and galaxies, the science of astrophysics took a huge leap forward.
Astronomers use specialized instruments called spectrographs, which were first used by chemistry researchers to study the spectral fingerprints of elements in the lab. (Read more about them here). Astronomers employ spectrographs to break up the light from stars, galaxies, planets, nebulae, etc. into its component wavelengths. The data from these instruments is then plotted, which lets the researchers analyze the chemical signatures in the light and compare them to the signatures of known elements.
The "prism" view of a spectrum of a star with hydrogen in its atmosphere might look something like the images below. The top image shows what it looks like when hydrogen absorbs light as it is emitted from an object. This means that hydrogen exists in or near the object. The bottom image shows what it looks like if hydrogen is emitting radiation (while it is heated). Each chemical element has a unique absorption fingerprint.
Each element has a typical "absorption" pattern that shows up in the spectrum of a star where the element exists. An object in space can also have an emission spectrum, which tells us that some element is being heated and glowing brightly. There's a rather nice tutorial about spectra here if you're interested in learning more about them.
So, the short answer to the query about how the astronomers figured out the chemical makeup of the star HE 0437-5439 is, they studied the light it radiates and compared what they found to the known chemical signatures of elements, particularly metals. They then compared THAT information to spectral studies of regions in the LMC. From that, they can draw a pretty good assumption that the star came from that region.
One other thing about spectra: you can also tell an object's velocity through space and the direction it's traveling, all using spectra. There's a gold mine of information locked away in the light and other wavelengths of radiation being emitted from objects in space. It's an amazing treasury that astronomers tap into every time they study an object through a spectroscope.)
The sites below belong to space and astronomy enthusiasts. I make every effort to check them and make sure they are still appropriate. However, I am not responsible for their content, nor do I endorse any of it by simply linking to them. As with all Web surfing, please exercise caution.
Adot's Notblog A fellow traveler blogger and astronomy enthusiast!
Astronomy Blog An astronomy blog pondering the big questions
