Doing Astronomy Through Chemistry

It’s Elemental, Dear Watson

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.

Hydrogen absorption spectrum, courtesy www.solarobserving.com.

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.)

6 thoughts on “Doing Astronomy Through Chemistry”

  1. I like astranomy & chimistry both.I study chimistry in university & I’d like to get more information about this science

  2. I’m currently majoring in chemistry and I would like to involve astronomy as well. What kind of jobs can a person get by majoring in chemistry and astronomy?

  3. am currently in the field of chemistry and am fond of astronomy and the both related in spectroscopics which overwhelm me to enhance my views into it. thanks to the SPACE WRITER Ms. CAROLYN COLLINS PETERSEN.

  4. I’m currently doing my masters in chemistry and I like to study astronomy as well. Is computational and theoretical chemistry a good field to become an astrochemist?

  5. Most of the folks I’ve worked with in the field have a lot of experience with spectroscopy, so you should get some background in that. Theoretical could be useful, although I’m not sure what all that covers.

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