This past week, I’ve been working at Kitt Peak National Observatory’s WIYN telescope using one of the workhorse instruments called HexPak to help astronomers better understand how galaxies work. At left is a photo I took of the galaxy M51 with the New Mexico State University 1-meter telescope. While we can learn a lot studying photos like this, wouldn’t it be nice if we could learn more, and understand what chemical elements make up the different parts of a galaxy? The instrument HexPak is designed to do just that.
One of the best tools we have for understanding the chemistry of objects in space is spectroscopy. Back in the nineteenth century, it was discovered that if you looked at heated elements through a spectroscope, you would see a characteristic set of lines in the rainbow-like spectrum. These lines are like a fingerprint for each element. It turns out that stars are really good at heating up elements! Below is a photo of the WIYN telescope with HexPak mounted.
HexPak is the white hose-like thing on the right plugged into side of the telescope. Inside that hose-like unit is a bundle of optical fibers arrayed in a hexagonal pattern. They look like this:
We can then align those fibers with a galaxy like M51 above, so different parts of the galaxy line up with different fibers. When that’s done, it looks something like this:
Now, I should note, this image was created just for illustration purposes. I haven’t tried to match the scale or alignment of my NMSU 1-meter image of M51 with the HexPak fiber array. However, you will see that different parts of the galaxy now line up with different fibers. That light is now sent downstairs to a bench spectrograph where it’s broken into its component parts. Here’s WIYN’s bench spectrograph. You can even see the rainbow like spectra on the grating at left we use to analyze the light from galaxies.
Light from each of the fibers in the array becomes a single spectrum and the image of that spectrum is recorded on a camera, shown at the right of the image above. Each one of those spectra will tell us about the elements present in each of the parts of the galaxy as lined up above. So, for example, you can figure out if the spiral arms have different amounts of a certain element than the bulge in the center. You can see what’s going on in the space between the galactic arms. If you look closely at my photo of M51, you’ll see it has bright regions that line up with parts of the spiral arm. An instrument like HexPak can help an astronomer learn if those parts of the spiral arm are different from other parts of the spiral arm, and maybe see what those regions are made of.
As I’ve mentioned in other blog posts, this work does inspire my writing. Sometimes I look at a galaxy like one we study with HexPak and think what it would be like travel between the different parts of a galaxy. M51 has a lot in common with our own galaxy. What’s it like in the arms? What’s it like between the arms? What’s it like the galaxy’s center? What’s more, working with astronomers in the control room sometimes does feel like being a crewmember on a spaceship exploring uncharted reaches. All of these elements have influenced science fiction stories like Firebrandt’s Legacy and The Pirates of Sufiro. I’m getting ready to release the former and I’m rewriting the latter with help from supporters at my Patreon site.
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