Astronomers recently played a major role with skipper charge-coupled devices on the 4.1-meter Southern Astrophysical Research Telescope in capturing the first astronomical spectrum, an accomplishment made possible only by this new technology.
The low-noise and very accurate observations, hitherto impossible with any other device but now a reality owing to recent advances in skipper CCD technology, herald a new age of observation in astronomy that sets the scene for future scientific breakthroughs in cosmology and allied sciences.
The first astronomical spectrum was captured by skipper charge-coupled devices using an instrument installed on the 4.1-meter Southern Astrophysical Research Telescope. The results were presented on June 16 to the Society of Photo-Optical Instrumentation Engineers Astronomical Telescopes + Instrumentation meeting in Japan by Edgar Marrufo Villalpando, a physics PhD candidate at the University of Chicago and a Fermilab DOE Graduate Instrumentation Research Award Fellow.
Significance in Astrophysical Milestones
“This result is an archetype milestone for skipper-CCD technology,” said Alex Drlica-Wagner of the U.S. Department of Energy’s Fermi National Accelerator Laboratory, who led the project. “It really puts to bed many of the concerns about the viability of this technology for future DOE cosmology programs and really solidifies its place.”
The project was initiated as a Laboratory Directed Research and Development program at Fermilab in partnership with NSF’s NOIRLab detector group. LDRD includes a congressionally mandated national initiative sponsored by the DOE to empower its national laboratories to internally fund pioneering research and development ventures that explore novel concepts.
Historical Background and Achievements in Technology
Invented in the US in 1969, forty years on, CCDs took the Nobel Prize in Physics for having changed the game. These devices turn incident photons into electrons using two-dimensional arrays of light-sensitive pixels. Now ubiquitous in traditional CCDs, not only digital cameras, where they found their first application, but also in scientific imaging applications, mostly in astronomy, are limited by an electronic noise inherent in their operation.
One of the primary objectives of cosmologists is to unravel the mysteries of dark matter and dark energy by studying stellar and galactic distributions. These distributions call for state-of-the-art technologies that would most sensitively allow the detection of faint and distant celestial objects with the least possible noise.
Skipper CCDs: A Breakthrough in Low Noise
Modern CCD technology enables such measurements, but at the cost of either longer exposure times or reduced sensitivity. Thus astrophysicists often extend observations on the world’s largest telescopes to boost signals, or attempt to cool down electronic noise.
Introduced in 1990, skipper CCDs circumvent this problem by lowering electronic noise to a level where single photons can be precisely measured. Using a new technique, skipper CCDs read some pixels hundreds or thousands of times but skim over most of them, improving the accuracy of measurement in certain areas of an image while reducing the time needed for readouts.
First Use of Skipper CCDs in Astronomy
Although skipper CCDs first appeared in 2017 in the context of dark matter experiments such as SENSEI and OSCURA, the application of skipper CCDs for the observation of celestial phenomena presented in this development is the first of its kind. Importantly, the study described here used skipper CCDs with the SOAR Integral Field Spectrograph for the first time on March 31 and April 9 to observe galactic clusters, quasars at far distances, a galaxy with pronounced spectral lines, and a star that could be related to a dark-matter-dominated ultra-faint galaxy. This new application posted subelectron readout noise and distinguished single optical-wavelength photons, the first demonstration of this in astrophysical observations with a CCD.
Edgar Marrufo Villalpando was awestruck at the mention of this capability: “It’s stunning to think that we can capture photons that have traveled billions of light-years to our detectors and measure each one individually.”
Impact and Future Implications of Skipper CCDs
Scientists are sifting through that data from the first-ever observations now, and the second run with the skipper-CCD instrument on the SOAR Telescope is slated to happen July 2024.
Speaking to the remarkable development, Jim Janesick, the inventor of skipper CCD and a distinguished engineer at SRI International, reflected, “Decades have passed since skipper CCD was conceptualized—making this comeback quite astonishing. The results for noise reduction are simply astounding. I was quite surprised at how clean the statistics turned out to be.”
Advancements and Prospects in Skipper CCD Technology
After the first validation of skipper-CCD technology for astrophysics, scientific communities are very keenly developing its capability. The next generation of skipper CCDs will enroll a sixteenfold increase in speed than the previous ones; these new devices are under development jointly by Fermilab and Lawrence Berkeley National Laboratory. This new class of devices will reduce the readout times drastically, and active laboratory tests tend to fine-tune their efficiency and accuracy for astronomical observations.
Skipper CCDs are a new frontier of astronomical instrumentation, particularly in the quest for knowledge on the origin of the universe. The next-generation detectors will be able to reach read-out noise below a single electron and observe single photons coming from celestial objects, allowing open doors in a definitive change in the way that astronomers do research about the universe. The precision that skipper CCDs provide permits pushing even the faintest signals from galaxies, quasars, and other astronomical phenomena into a legacy of formation, evolution, and interactions on cosmic timescales.
Successful skipper CCDs in acquiring astronomical spectra thus open up qualitatively new opportunities for solving cardinal problems of astrophysics.
Looking ahead, the continued improvement of skipper CCD technology shows an increasingly wide acceptance by the astronomical community as a whole. On becoming stronger and more efficient, these detectors hold the potential to enable innovations in very different areas, from exoplanet research through galaxy formation and evolution to the hunt for dark matter. Improving the ability to detect very small signals with low noise will enable astronomers to make much more extensive maps of the universe and discover new cosmic phenomena, improving our understanding of already known ones.
More importantly, the partnership that exists between research institutions and national laboratories towards the development of Skipper CCDs underlines concerted institutional efforts towards pushing the frontiers of instrumentation in science. Such synergy not only engenders technological innovation in this field but also international partnerships toward the basic scientific knowledge. While skipper CCDs continue to harness their power to make constructive, pioneering astronomical observations, they are positioned to become irreplaceable tools for future missions and endeavors that seek the universe’s deepest secrets.
Finally, a special application of skipper CCD technology is also foreseen beyond the field of astronomy. It has ultra-sensitive photon detection capabilities, so it becomes one of the potentials for realizing improvement in a wide range of areas, from medical imaging to experiments in particle physics where very precise measurements have to be taken at the quantum level. The ability to detect individual photons with extremely low noise levels offers opportunities for new discoveries and innovations across numerous scientific fields of inquiry, paving the way for future technological breakthroughs that could redefine our whole understanding of the cosmos or even the very blocks that compose matter.