Assembling the Puzzle

This has been another week helping to install the Dark Energy Spectrographic Instrument or DESI at the Mayall 4-meter telescope at Kitt Peak. In short, the goal of DESI is to study the effect of dark energy on the expansion of the universe. We plan to collect spectra of tens of billions of galaxies and quasars with the goal of making a three-dimensional map of the universe out to about 11 billion light years. You can read more about the DESI project at https://www.desi.lbl.gov/

The DESI project is spearheaded by Lawrence Berkeley Lab in California and being installed at Kitt Peak in Arizona. However, it really represents a worldwide collaboration. There are scientists working on this project from England, France, Spain, Italy, South Korea, China, France, Canada, Colombia, Australia, and others plus numerous institutions within the United States. All of these agencies are not only contributing expertise, but actually building components that will go into the finished instrument.

In an earlier post, I spoke about how we worked to remove the Mayall telescope’s original top end. The top end originally housed both a secondary mirror and a prime focus camera. Both of these have been used to make groundbreaking discoveries over the last five decades. The Mayall was the telescope Vera Rubin used to study rotation curves of galaxies, which led to the discovery of dark matter. I’ve helped with observations that have led to the confirmation of numerous exoplanets. We’re now replacing the telescope’s original top end with a new one that will hold 5000 fibers at prime focus. Each of those fibers will run to spectrographs that will break up the light from objects in the sky so it may be analyzed and the position of the object can be measured. In the photo above, you can see the new top end being assembled to the left of the telescope.

To get light from the sky onto the fibers, the telescope will collect it with the primary mirror. That sits in the big white structure at the center of the big blue horseshoe-like structure in the photo above. The mirror will direct that light to the top end. Because the mirror is curved, allowing the light to be collected and redirected, it means the focus changes across the field of view. To deal with that, you need to put some lenses in front of the fibers, sort of like glasses. Another real world problem of telescopes is that as you point toward the horizon, light gets spread out. So you need optics to compensate for where you’re pointing in the sky. Sort of like glasses that automatically adjust themselves for where you’re looking.

Scientists from England assembled those specialized “glasses” for the telescope. Those arrived last week and I was on hand during their assembly at Kitt Peak. You see those assembled optics in the lower photo. Scientists from Italy built the “Hexapod” pointing system, which keeps those optics aligned. That arrived and was tested about a month ago. Scientists from Fermilab in Chicago are responsible for integrating those systems and putting them together in the top end ring. That process will start next week. It’s all quite a puzzle and it’s been remarkable to see it all come together. It’ll be even more amazing to see what science it yields.

Of course, work at Kitt Peak helps to inspire my science fiction. As a reminder, this is the last weekend of the Smashwords Summer/Winter sale. You can learn about my science fiction books that are on sale at:

We also have fantasy and steampunk titles on sale. You can learn about them at:

Advertisements

Ramping up the Refit

This past week, I’ve continued my work supporting the refit of the Mayall 4-meter telescope for the upcoming DESI spectrograph. DESI is the Dark Energy Spectroscopic Instrument and it will be capable of measuring of the spectra of 5000 objects at a time. Its mission objective is to collect data to help us understand the nature of Dark Energy in the universe. We don’t yet know what Dark Energy is, all we really know is that appears to make the expansion of the universe accelerate with time. To be able to collect these 5000 spectra, the telescope needs a new top end. Indeed, the first thing I saw when I came to work on Monday morning was the old top end sitting on a flatbed trailer outside the telescope being ready to go into storage.

The Mayall 4-meter is a reflecting telescope and the primary optical component is a big 4-meter diameter mirror at the bottom. The light from that mirror is then focused at that top end and either collected by a camera sitting there at “prime focus” or a sent down to an instrument underneath the telescope using a secondary mirror. The top end held both the prime focus and the secondary mirror and could be flipped end-for-end to allow either to happen. DESI will have its 5000 fibers in a new top end and indeed, part of the reason for selecting the Mayall was to have a telescope sturdy enough to handle that large an instrument. At the moment, the telescope is missing its top end, but the new one will be installed soon. There are work platforms, which enabled people to loosen the old top end so it could be lifted out with a crane. The work platforms also keep the telescope structurally stable while there’s no top end in place.

The top end only holds part of the instrument. It will have 5000 optical fibers which may be precisely positioned onto target objects. The light from those fibers is sent along the fibers to spectrographs in an environmentally controlled room where the light will be spread out and photographed so it can be analyzed. In the dark energy survey itself, most people will be looking at the so-called redshift—how far the characteristic spectral “fingerprint” of certain chemicals shifts to the red as a result of its velocity away from us. However, those same chemical fingerprints may be used to understand properties of the objects being looked at and this data will be available to anyone who wants to use it.

Because dark energy is an exciting topic in its own right, but also because this project will be generating so much raw data that’s useful to so many astronomers, it’s a major worldwide undertaking. To break the light from the fibers into spectra will require ten spectrographs which will reside in a carefully climate-controlled room. An exciting milestone I got to watch this week, was unpacking the first of those spectrographs when it arrived from France. Below, you can see the engineers inspecting the optical elements. Note the rainbow visible on the corrector plate of the right-most optical element. That’s exactly what this device is built to do! Break the light into rainbows.

Today finds me in Phoenix, Arizona for Leprecon 44. If you’re in town, I hope you’ll drop by and check out some of the panels and workshops.

Refitting the Mayall: Teardown

I was in 8th grade when Star Trek: The Motion Picture came out. One of the things that fascinated me in that movie was the refit of the Starship Enterprise. I was captivated by how the ship looked at once much the same and yet completely different. It looked sleeker and more powerful and familiar space on the ship such as the bridge, sickbay, and the transporter room had all been updated. I’m getting to experience something much like the Enterprise refit in real life. In this case, I’m involved in refitting the Mayall 4-meter telescope at Kitt Peak National Observatory.

Like the Starship Enterprise, the Mayall has a forty-five year history of discovery. Originally built to use photographic plates, the telescope has played an important role in such discoveries as establishing the role of dark matter in the Universe from measurements of galaxy rotation, and determining the scale and structure of the Universe. Over the years, new instrumentation has been added to the telescope including advanced digital cameras and spectrographs.

The purpose of the refit is to install a new instrument called DESI, which stands for Dark Energy Spectroscopic Instrument. 5000 optical fibers will be installed at the telescope’s prime focus (the top end of the telescope) and run to cameras in another room. The goal is to observe tens of millions of galaxies and quasars, constructing a three-dimensional map spanning the nearby universe to 10 billion light years.

In order to achieve this goal, the entire top end of the telescope has to be replaced and much of the control software and electronics are being redone so that it’s truly state of the art. To achieve this goal, we literally have to gut the telescope and install new components from the inside out. During my most recent shifts at the telescope, I’ve been involved in just that. In the photo to the right, you can see that the bottom of the telescope is missing and replaced with scaffolding. That’s because the large 4-meter mirror is out for recoating. Also, all the optics are missing from the secondary mirror assembly at the top of the telescope. Ultimately, that will be removed completely and replaced with a new secondary ring. The men in the photo are removing a counterweight assembly used to precisely balance the telescope when instruments are added and removed. Electrical panels are open on the side of the telescope where control cabling going back to the photographic days will be removed and replaced with new control cabling. Modern electronics mean the telescope will have about 10% of the cables as it did when originally built!

The refit has also allowed me a rare opportunity to see parts of the telescope I’ve never been to before, even after operating it for some thirteen years. Earlier this week I got to help the electronics technicians work on some cabling in the “horseshoe.” That’s the big, blue horseshoe-shaped mount you see in the photos above. We actually ended up working down in the broad, blue, oval-shaped tube you see in the photo just above. I dubbed it the sinking submarine, because it’s a cramped space and we were standing at a 32-degree angle relative to the ground!

It’s going to be exciting to watch the telescope take shape again after the teardown process. New parts will be arriving in the coming months. A large crane will be deployed outside the 4-meter to lift out the old secondary ring and bring in the new one. The plan is to be back on sky to test components of the new instrument later this year. Once those tests are completed, other components will be finished, revised if needed and then installed. At that point, the Mayall’s new five-year mission to map the universe will begin.


Hunting Asteroids

I rang in the new year by helping Robert McMillan, Jim Scotti, and Melissa Brucker from the University of Arizona hunt for potentially hazardous asteroids in our solar system at the Kitt Peak 4-meter telescope. This is important work since asteroid impacts are one of the few completely predictable and preventable natural disasters. Here I am at the telescope console.

As it turns out, this observing run was something of a bittersweet milestone. Bob, Jim, and Melissa are the last scheduled visiting observers on the 4-meter. At this point, we have about five more weeks of observing with a scheduled imaging survey program and then the telescope shuts down so it can be refitted with an instrument called the Dark Energy Spectroscopic Instrument, or DESI. DESI will measure the effect of dark energy on the expansion of the universe. It will obtain optical spectra for tens of millions of galaxies and quasars, constructing a 3-dimensional map spanning the nearby universe to 10 billion light years.

So, what about the asteroids? Well, the good news is that there are smaller telescopes on Kitt Peak devoted to the search. The reason Bob, Jim, and Melissa use the 4-meter is that it allows them to look for more distant asteroids on nights when the small telescopes are not as effective. In this case, we were attempting our observations during the full moon. Because the moon is so bright, it’s hard to see faint, distant objects with small telescopes because you need to expose on the sky for a long time. The 4-meter can take shorter exposures and still detect these faint objects without having the skylight swamp the exposures. In the meantime, Bob, Jim, and Melissa have applied for time on other telescopes around the world to do the work they were doing on the Kitt Peak 4-meter.

Often times when I’m involved in these runs, I’m asked if I’ll let people know if something is going to fall on us. Well, if I know, I’ll tell. However, what we often do is identify small objects a long ways away. It’ll usually take more than the observations we get to determine the object’s orbit and find out whether or not it presents a serious hazard.

So what actually happens if we discover an asteroid that might hit the Earth? I found this NASA video that gives a nice explanation. I notice there is also an image credit from my friend Mike Weasner, a talented amateur astronomer who is also a science fiction fan.

If you want to get more of a sense of what life is like behind the scenes at an astronomical observatory, be sure to read my novel The Astronomer’s Crypt. You can learn more about the novel and get a sneak peak at http://www.davidleesummers.com/Astronomers-Crypt.html

The Biggest Explosions of All

I’ve spent a lot of time in my astronomy career pointing telescopes at some of the biggest explosions of all—type 1a supernovae. This kind of supernova starts with a white dwarf star and another star orbiting each other. White dwarfs are very dense stars at the end of their lives. The only objects more dense are neutron stars and black holes. The white dwarf’s gravity draws material off the companion star until it reaches critical mass and the whole thing explodes. One such star that I had the chance to observe in detail in was Supernova 2011fe in the galaxy M101. Here’s an image from the Mayall 4-meter at Kitt Peak, one of the telescopes I used to observe this object. The supernova is the bright blue star outshining everything else in the upper right-hand part of the image.

Image by T.A. Rector (University of Alaska Anchorage), H. Schweiker & S. Pakzad NOAO/AURA/NSF

These cosmic explosions are pretty interesting in their own right. Our own star is expected to end its life as a white dwarf and these explosions give us a glimpse at the hearts of these stellar corpses. These explosions are also one of the ways heavy elements formed in the cores of stars get distributed out into the universe. Supernova 2011fe was, in fact, one of the closest Type 1a supernovae we’ve ever observed. We caught the explosion soon after it happened, watched the supernova brighten to maximum, then start to fade away.

Type 1a supernovae also have another useful property. Because white dwarfs have a fairly uniform mass, the brightness of the explosion is also uniform. So, if every Type 1a supernova observed were placed at the same distance away from you, they would all, more or less, be the same brightness. This means that by measuring the apparent brightness of the supernova, you can figure out how far away it is. This is a bit of an oversimplification, but there are ways to calibrate that information based on the how fast the explosion brightens and fades.

Back in the 1990s, an astronomer named Saul Perlmutter was granted target-of-opportunity time on Kitt Peak telescopes. In this case, it meant if a type 1a supernova went off, he could ask the telescope to point to it and take an image and calibration data. He and his colleagues hoped to get distances to as many galaxies as possible. I helped acquire some of that data which was combined with a lot of other data from a lot of telescopes to provide evidence that the expansion of the universe is accelerating. Perlmutter would go on to share a Nobel prize with Adam Riess and Brian P. Schmidt for this work.

This is one of those discoveries that shows some of the true fun of science. We learned that the expansion of the universe is accelerating, but that raises an even bigger question. Why is it accelerating? Typically that’s attributed to something called “Dark Energy.” This attribution isn’t meant to be an answer in itself. It’s meant to be a placeholder. It’s “Dark” energy because we don’t know precisely what kind of energy it really is, or even if it’s energy at all! Later this year, a new instrument called DESI will be installed on the Mayall 4-meter which will endeavor to get answers to some of those questions. But like all good science, I expect a veritable explosion of new questions raised for every answer we’re able to get.

On Turning 50

Over the weekend, while at TusCon in Tucson, Arizona, I celebrated my fiftieth birthday. It’s one of those points in life where I find myself looking back to see where I’ve been as well as looking forward to see where I’m going.

david-at-50

In my first fifty years, I’ve written and published nine novels, eighty-four short stories, and fifty-four poems. I’ve edited three anthologies, plus two magazines for ten years each. I contributed to the commissioning of the WIYN 3.5-meter telescope and the NMSU 1-meter telescope. I’m co-discoverer of two variable stars and I helped take data that contributed to the discovery of dark energy. Most of all, I’m proud to be the father of two incredible young ladies, one in high school, the other in college, who have a wide range of talents in such areas as computer science and mathematics.

Looking ahead, my tenth novel, The Astronomer’s Crypt, is nearing release. I have two anthologies in the publication queue: Kepler’s Cowboys and Maximum Velocity: The Best of the Full-Throttle Space Tales. I have four short stories accepted and awaiting publication. Beyond that, I’m in the early phases of writing a new novel and I have a “fix-up” novel a little over half completed. Plus I have story treatments for four more novels. Presuming no major funding shifts, I expect to be involved in commissioning two new instruments at Kitt Peak in the coming years.

As I reach fifty, I’m arguably in the best health I ever have been. The arthritis that plagued me for years is in remission and I regularly take long walks through my neighborhood. Nevertheless, one specter looms over me. My dad was only fifty-two when he died suddenly of a heart attack. In the plus column, my doctor is helping me watch my heart health and both of my brothers have now outlived my dad by over a decade. I have no immediate reason to fear for my imminent demise. Nevertheless, I find myself grieving for how truly short my dad’s life was cut and watching my health has taken on a new urgency.

In short, as I turn fifty, I feel proud of what I’ve accomplished. My regrets are minimal. While there are some harsh words and rash actions I’d take back if I could and some friends I’ve lost touch with over the years, it’s hard to say I’d have a better life if I’d taken a different path. I have several exciting things to look forward to in the coming months and years, plus plans and goals for the years beyond that.

Thanks to my readers for sharing some of this fifty-year journey with me. I look forward to sharing the coming years with you as well.