DESI Naked!

This weekend finds me at Bubonicon 51 in Albuquerque, New Mexico. I’m moderating panels about space cowboys and large scale scientific surveys. If you’re in town, click the link to get the details and drop by. I’d love to see you there. Of course, part of my interest in large scale scientific surveys has to do with the work I’ve been helping with over the last year and a half, installing the DESI Spectrograph at the Mayall 4-meter telescope at Kitt Peak National Observatory. During my my recent shift at the observatory, I got a rare look at the new instrument not just “under the hood” but before the hood even went on.

In the photo above, you see DESI on the left, just over the orange platform. Standing on the ground floor in the foreground are just a few of the telescope engineers and technicians who have been installing this new, innovative instrument which will be used to make a 3D map of about a third of the known universe. DESI itself is an array of 5000 fibers mounted on robot positioners that can be precisely centered on targets each time the telescope moves. The light from those objects then travels down fibers two stories below. The fiber bundles are ready to be run along the telescope. You see them coiled up on the white carts to the lower right of the photo above. Each black cable contains 500 fibers. One of my jobs this week was labeling those cables so people can keep it straight which cable is which as they run them along the telescope.

Here are all the DESI fiber positioners mounted to the telescope. You can see each of the ten cables coming up into ten sets of fiber positioner “petals.” Each of these petals was installed into the telescope with great care about a month ago. Light was placed on all the fibers and it was confirmed that in all the transportation and installation, none of the fibers were broken. All of them transmit light as expected! This week, the control electronics are being wired up and routed through the telescope. Once this chore is complete, more testing will happen to assure that the fibers still transmit light and each of the robot positioners moves as expected using the electronics routed through the telescope.

All of those fibers will eventually come into a clean room downstairs to a series of ten spectrographs. Do you begin to sense a pattern? Ten petals, ten cables, ten spectrographs. As it turns out, another job of mine this week was helping to install the seventh spectrograph, which you see in the lower right of the photo above. Western fan that I am, I feel like you can now cue Elmer Bernstein’s score for The Magnificent Seven. Of course, that won’t last long. soon we’ll have an eighth, ninth, and tenth spectrograph.

Each of those spectrographs will be used to examine the light from 500 fibers. To make the map, we’ll be using these spectrographs to see how far characteristic chemical lines in spectra have shifted from where they normally sit within the rainbow toward the red end, which is one measure of how far away those objects are. We’ll compare that to statistics of how far apart they are, which turns out to be another measure of how far away they are. That said, just because we’re mostly looking for the redshifts, there will be all kinds of other spectral data available that can tell astronomers all kinds of information about properties of galaxies all over the sky. One of the most exciting things about the DESI program is that this data will be available to all. In this post, I may be laying DESI bare for all to see, but the whole project will be laying much of the universe bare, and in the process expanding the body of astronomical knowledge.

  • For a fictional and frightening look behind the scenes at an astronomical observatory, read The Astronomer’s Crypt.
  • To take a tour through the wonders of the solar system, read The Solar Sea.
  • To travel back in time to the Old West, check out Owl Dance!

Exploring Galaxies

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.

You can get involved in the fun by becoming a patron. My patrons are the first people who get to read new stories in my science fiction universe and they get to download complete books when they’re available. What’s more, one of my goals at my Patreon site is to make this blog ad free. If you like behind-the-scenes looks into astronomy like this one, but don’t like the ads at the blog, please consider supporting my Patreon site at: http://www.patreon.com/davidleesummers

Cosmos: A Spacetime Odyssey

The autumn of 1980 was perhaps one of the most difficult times of my life. My father died suddenly of a heart attack just about six weeks before my fourteenth birthday. One thing that helped pull me through that difficult time was Carl Sagan’s original Cosmos. It fostered my love of astronomy and set me on a course that would eventually earn me a degree in physics. Thirty-five years later, I’m now sharing Neil deGrasse Tyson’s updated Cosmos with my daughters. My youngest is the same age I was when I discovered Sagan’s original.

Cosmos: A Spacetime Odyssey_titlecard

Overall, I’ve been impressed with the series. I can nitpick some places where they’ve sacrificed precision in how a particular astronomical object or phenomena is depicted in the name of dramatic effect, but for the most part Tyson gets the important things right. The show has allowed me to better explain the importance of spectra in my work at Kitt Peak. I was delighted to see an episode featuring Henrietta Leavitt, Annie Jump Cannon, and Cecilia Payne-Gaposchkin. I was able to discuss how they influenced both my work and how people they worked with directly inspired teachers of mine such as Emilia Belserene at Maria Mitchell Observatory. I also appreciated the discussion about how neutrinos can precede supernova explosions, though I noticed they managed to leave out mention of Stirling Colgate’s important contributions to that work.

Perhaps the most important thing about the series is that I see the same wonder on the faces of my daughters that I had when I watched Carl Sagan’s original series. My oldest daughter has already set her sights on a degree in mathematics and computer science. My youngest still has options wide open. I hold no strict expectation she’ll pursue a career in science, but I do expect she’ll come to respect the process of science and hold an appreciation of it no matter what she does.

Unlike Neil deGrasse Tyson, I hold no Ph.D. My career in astronomy diverged from a strictly academic path into more of an engineering and support path. Despite that, I feel it’s important to convey my love of science in classrooms as well as science fiction and steampunk conventions. In fact, I think there’s value in showing that you don’t need a Ph.D. to appreciate, use, and act on scientific discovery. Because of my interest in communicating about science, I’ve been paying close attention to Tyson’s presentations. He is a good, clear communicator and I’ve especially enjoyed seeing how he introduces subjects such as stellar spectroscopy, supernovae, and black holes.

In the most recent episode I watched, Tyson presented the sobering evidence for climate change. There’s been a lot of debate about it, but as he notes there’s well over a century of solid evidence that carbon dioxide is increasing and global temperatures are warming. He notes that weather is hard to predict and there are lots of minute variations. He demonstrated this by walking a dog. The dog goes all over the place, attracted by different things. However, climate is like the man holding the leash. There may be random variations, but there’s also an overall path. Although climate change is a sobering reality, I appreciated that Tyson showed that there is hope. We have to work hard and make solar and wind energy a reality and we need to do it much faster than we have been.

Now some will say addressing climate change is just too big a problem to address. I watched this episode after visiting New Orleans ten years after Hurricane Katrina. Ten years ago, some people said rebuilding New Orleans was just too big a challenge, we should let the city go. Although Katrina still echoes in New Orleans, it’s returned to being a bright and vibrant city. Researchers at Tulane University are working on finding ways to restore the gulf coast and perhaps even find ways to make New Orleans much safer should another hurricane strike. We humans are amazing and we can solve the big problems when we set our minds to it.

I appreciate the effort Neil deGrasse Tyson, Ann Druyan, and Seth MacFarlane have put into bringing a new version of the show back. I hope it inspires a new generation to look at the world with wonder and to take the scientific process seriously.