Stars, Galaxies, and Fiber Optics

The first time I remember learning about fiber optics was in a behind-the-scenes article published in 1980 or so about the making of Star Trek: The Motion Picture. The article talked about how they got light to all the buttons on the bridge set and showed them illuminated with bundles of optical fiber. Nowadays, as I’ve mentioned in several earlier posts, I work with instruments that use optical fiber to carry light collected by each of the telescopes I work with to the instrumentation where its analyzed.

On the telescope side, those fibers are attached to an optical assembly that must be placed at just the right spot to catch focused light. If the star or galaxy is out of focus, not all the light goes down the optical fiber. We also have guider cameras that work to keep the object precisely aligned on the fiber so all the light gets to the spectrograph. It’s a lot of complex hardware to work right to precisely measure the the redshift of distant galaxies or look at a star and determine whether or not it has planets in orbit. This past week, we’ve been commissioning both the DESI spectrograph at the Mayall 4-meter and the NEID spectrograph at the WIYN 3.5-meter. One of the most important milestones is to get light from the object you want to measure to the spectrograph and see if you get the flux you expect. Here’s the NEID team at WIYN looking at early test results.

Yes, light leaves a star dozens of light years away, enters our telescope, goes down the optical fiber and is photographed with the spectroscope, then all that data can be viewed and analyzed on a laptop computer. When I filmed the trailer for The Astronomer’s Crypt a couple of years ago, I was asked why we didn’t use a room full of fancy computers and monitors. We just had a couple of computers, one of which was a laptop. The reason is that I’ve seen a lot of control rooms where simple computers are the only ones present!

As you can imagine, it’s quite a relief to see all the work pay off in a spectrum that shows the flux level you expect. All of this is pretty exciting stuff and, as it turns out, my birthday fell during this past week’s tests. Seeing NEID as it nears readiness for scientific use is pretty exciting in its own right, but we had another surprise on the day of my birthday. Ethan Peck, who plays Spock on Star Trek Discovery, was on a road trip and decided to visit the observatory. A tour was arranged and he spent the beginning of the night at the WIYN telescope. For me, it was quite a thrill to have Spock, of all people, wish me a happy birthday! He brought a Polaroid camera with him and we snapped a photo of us standing by my control station. Here we are at WIYN. Ethan Peck is in the center (in white) and I’m to the left.

Meanwhile, across the mountain at the Mayall 4-meter, commissioning has continued on the DESI instrument. The instrument had its official “first light” a couple of weeks ago and a wonderful image was released that, I think, really illustrates the power of DESI.

Image credit: DESI Collaboration, Legacy Surveys; NSF’s National Optical-Infrared Astronomy Research Laboratory/NSF/AURA

Here you see an image of all 5000 DESI fibers superimposed on the sky. At the bottom of the fiber array is M33, the Triangulum Galaxy. Below that is a view of the spectrum from just one of the 5000 fibers showing the light from that little piece of the galaxy. In it, you can see the lines labeled that denote the presence of hydrogen, oxygen, nitrogen, and even sulfur. Now remember that each fiber in that picture gives the same kind of data for the piece of sky its on. You can read the full press release about DESI’s first light at: https://nationalastro.org/news/desis-5000-eyes-open-as-kitt-peak-telescope-prepares-to-map-space-and-time/

All of the robotic positioners moving those fibers at the top of the Mayall telescope get hot and there’s a chiller system to keep them cool. This week, that chiller system will be automated, but last week, we had to monitor it by eye and it requires a person to turn the system on and off by hand. The person doing that remarked how spooky it is to be in the depths of the Mayall with all the lights out and remarked how she kept looking over her shoulder, wondering if someone was there. This is another aspect of my job that definitely helped to inspire The Astronomer’s Crypt. You can learn more about the novel and see the trailer I mentioned earlier at http://www.davidleesummers/Astronomers-Crypt.html.

Making Instruments Work

Today, I’m at the TusCon Science Fiction Convention in Tucson, Arizona. You can get all the details about the event at http://tusconscificon.com. One of the topics I’ll be speaking about is the work we’ve been doing for the last year, installing the DESI Spectrograph on the Mayall 4-meter telescope. At this point, installation is nearing completion and we’re beginning the process of commissioning the instrument. In short, we’re actually making it work with the telescope so we can get the data we hope to obtain.

DESI isn’t the only instrument that we’ve recently installed. We’ve also installed the NEID spectrograph on the WIYN telescope. While DESI has the goal of making a 3D map of about one-third of the sky, NEID has the goal of looking for planets around other stars. I’ve shared quite a bit about the DESI installation because that instrument is of a scale that it required a major refit of the telescope. The NEID spectrograph has involved a similar amount of time in development, but much of that development has happened off site at places such as Penn State University and the University of Wisconsin. NEID, which rhymes with fluid, takes its name from the Tohono O’Odham word meaning “to see.”

Two weeks ago, the port adapter, built by the University of Wisconsin, and the spectrograph, built at Penn State University, both arrived at WIYN and have been installed at the telescope. You can see the port adapter on the side of the telescope in the photo above. It’s job is to capture light coming through the telescope from a distant star and feed it into fiber optics that run downstairs to a high precision spectrograph.

The spectrograph itself lives in a clean room on the WIYN Observatory’s ground floor. To get the kind of precision needed to see planets around other stars, the temperature within the spectrograph must be carefully maintained and the spectrograph elements must be kept in the same relative position. Footsteps nearby could disturb this device. Because of that, the spectrograph itself is built inside a coffin-like housing. Once the Penn State team gets everything set up, they’ll seal up the coffin and, unless there’s a serious problem, no one will look inside again. I got to peak inside the spectrograph a few days ago and it may be my only view.

Now that the instrument is installed at the telescope, we have to make sure everything works as it should and programmers are working to make sure we have software to assure we can efficiently get the data we need. We’re starting with the port adapter itself. I point the telescope at stars and a team of scientists and engineers check the function of the various parts within the adapter to make sure they understand the alignments on the sky, which are necessary for tracking the stars. They check the tip-tilt electronics, which make sure we get as much of the star’s light as possible down the fiber, and make sure all the calibration functions work. After this, work will begin commissioning the spectrograph itself. This is a process which takes a few months to complete to assure we’re getting the performance out of this instrument that we want.

Commissioning nights are very different from normal observing nights at a telescope. On a normal observing night, it’s often me and an observer. Often the observer isn’t even at the telescope, but working from their home institution, controlling a camera on the telescope over the internet and talking to me through computer chat. On a commissioning night, I can have anywhere from five to fifteen people in the control room with me, all working on different elements of the instrument. This marks a busy and exciting time as we get these new instruments ready for service at Kitt Peak National Observatory.

Stars Wobbling at the Speed of a Desert Tortoise

In recent posts about new observing projects at Kitt Peak National Observatory, I’ve largely focused on the DESI spectrograph which aims to create a three-dimensional map of the northern sky. In fact, I’m in Denver, Colorado this weekend at MileHiCon and I’ll be giving a presentation on this very subject. However, this isn’t the only new instrument I’m helping to deploy and commission.

At the WIYN 3.5-meter we’re installing a spectrograph called NEID. Kitt Peak sits on the land of the Tohono O’Odham people in Southern Arizona. The acronym is derived from the Tohono O’Odham word meaning “to see.” The actual acronym is: NN-EXPLORE Exoplanet Investigations with Doppler Spectroscopy. In other words, it’s an instrument that will be used to look for planets around other stars. Like the DESI spectrograph, fiber optics are mounted to the telescope and feed a spectrograph two floors below the telescope. Just over a week ago, I helped to run the fibers from the point the instrument will be mounted down to the spectrograph room. In the photo, you can see the fiber optic cable laid out like undulating waves at the base of the telescope. The instrument itself will be mounted at the round port that currently has the white, rectangular sign.

The way a spectrograph like NEID finds planets around other stars is by measuring how much they move toward and away from the Earth when they’re pulled by orbiting planets. You likely see spectra all the time. A rainbow is a spectrum of the sun. In a spectrum are characteristic lines caused by elements in the star’s atmosphere. When a planet tugs the star toward Earth, those lines move toward the blue end of the spectrum. When a planet tugs the star away, the lines move toward the red end. Of course, one of the hopes of exoplanet science is to detect Earth-like planets around other stars, or more specifically, Earth-sized planets in the zone around a star where water can be liquid. If you imagine watching our sun from another star, we’d see the Earth pull the sun toward or away from us at about 30 centimeters per second, or about the speed of a desert tortoise!

To see this small motion, you need to be able to see the spectra—the rainbow—at very high resolution. This is more than magnification. You need to see it at great detail. A spectrograph that can do that is often fairly big and it’s very difficult to mount it to the side of a moving telescope. This is why we use a fiber to capture the light and send it to a spectrograph in a different room. This allows the engineers to build the spectrograph as big as they need, but only requires them to mount the fiber to capture the light to the telescope.

Fiber optic cable is meant to be tough, but it can break, so it’s gratifying after we make the run to be able to shine light through the cable and see it at the other end, as we see in this post’s second photo!

Besides looking very specifically for Earth-like planets, the NEID spectrograph will be providing support for NASA’s Transiting Exoplanet Survey Satellite, or TESS, mission, which is searching for exoplanets around the closest stars to Earth. Once TESS discovers a planet, we can observe it with NEID and get more precise mass and density information about the planet. Such measurements help us better understand the composition and formation of the planets around other stars. It’s a very exciting time at Kitt Peak as we deploy these spectrographs which will help us understand both planets in our galactic neighborhood and the overall structure of the universe.

NEID – A New Way of Seeing Exoplanets

Last week, I talked a little about the work we’re doing refitting the Mayall 4-meter Telescope for the Dark Energy Spectrographic Instrument. However, it’s not the only construction going on at Kitt Peak. The WIYN 3.5-meter telescope, which I also work with, is getting a new spectrograph installed called NEID. Deploying NEID doesn’t require a full telescope refit like deploying DESI, but there’s still quite a bit of work happening in the building.

Most of the work right now is going into building a new bench spectrograph room. NEID is an acronym for “NN-explore Exoplanet Investigations with Dopler spectroscopy”. The word “neid” is also the Tohono O’Odham word meaning “to see.” An appropriate choice, given Kitt Peak’s location on the Tohono O’Odham Nation in Southern Arizona. The goal of NEID is to provide the astronomical community with a state-of-the-art Doppler spectrograph to investigate exoplanets around nearby stars.

The way this will work is that an optical fiber assembly will be mounted to the telescope itself at the port in the photo to the right with the sign on it. That optical fiber will carry the light from the star to the new bench spectrograph downstairs where it will be spread out, like a rainbow. The reason for doing this is not to see a pretty rainbow, but to see dark lines interspersed through the rainbow. Those dark lines are like the star’s chemical fingerprint.

Now, here’s the fun part. When a planet moves around the star, it drags the star just a tiny amount toward the Earth which causes that spectral fingerprint to shift a little bit toward the blue end of the spectrum. When the planet passes behind the star, it drags it away from the Earth and moves the spectral fingerprint toward the red end of the spectrum. Looking for this shift is the “Doppler” approach to finding planets that NEID will employ.

In addition to discovering new planets, NEID will be used to follow up observations by NASA’s Transiting Exoplanet Survey Satellite (TESS) and will help to determine masses and densities for planets TESS discovers. By the way, the NN-Explore that’s part of NEID’s acronym stands for NASA-NSF-EXoPLanet Observational REsearch. The current plan is to begin commissioning the instrument this fall and for regular observations to commence in 2019.

Being part of on-going research into planets around other stars is what inspired Dr. Steve Howell of NASA’s Ames Spaceflight Center and I to invite science fiction writers to imagine what these planets around other stars might be like. The results were our two anthologies, A Kepler’s Dozen and Kepler’s Cowboys. You can learn more about the anthologies by clicking on their titles.

Once NEID goes online and starts making discoveries, Steve and I may have to “see” into the future and collect a third anthology. This time, including stories about planets discovered by a telescope on a mountaintop in Arizona’s Tohono O’Odham Nation.