Dark matter is a mysterious and elusive form of matter that makes up about 27% of the universe's mass-energy content. It doesn't interact with light/electromagnetic radiation, making it undetectable through direct methods. Its existence is inferred from its gravitational influences on visible matter and the large-scale structure of the universe, playing a crucial role in the cosmos' overall dynamics.1-3
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Dark Matter Detection Challenges
The nature of dark matter remains one of the most challenging unsolved problems in modern physics. While astrophysical evidence strongly supports its existence, direct detection efforts, specifically through underground experiments using low-background detectors, have largely yielded null results with a few exceptions. The absence of predicted dark matter candidates on the large Hadron collider (LHC) energy scale further complicates the issue.1-3
Various detection methods have been used, including studying the cosmic microwave background radiation to understand the early universe’s matter distribution. Traditional approaches focused on gravitational effects and particle interactions have provided limited insight. Successful detection of dark matter would improve the understanding of its properties and also shed light on the formation and evolution of galaxies and the larger universe.1-3
Emergence of Near-Infrared Spectroscopy in Dark Matter Research
Near-infrared (NIR) spectroscopy is being explored to detect dark matter by observing the infrared photons emitted when dark matter particles like axion-like particles (ALPs) decay.4
Advanced telescopes like the James Webb Space Telescope (JWST) are particularly effective for this purpose, enabling scientists to search for faint signals from decaying dark matter particles amidst the universe's infrared background radiation. This technique has gained attention due to its potential to reveal dark matter signatures and provide deeper insights into the properties of dark matter through the analysis of NIR light spectra.4
A study recently published in Physical Review D used infrared spectrographs to explore the indirect detection of dark matter decaying into infrared light. The study demonstrated that astrophysical and thermal noise could be overcome. Specific instruments discussed include the Near-Infrared Spectrograph (NIRSpec) on the JWST and the Warm INfrared Echelle spectrograph to Realize Extreme Dispersion and sensitivity (WINERED) at the Magellan Clay 6.5 m telescope.4
The research showed that just a few hours of observations of a faint dwarf spheroidal galaxy using WINERED could probe ALP dark matter in the 1.8–2.7 eV (0.5–4 eV) mass range, with a photon coupling of gϕγγ ≳ 10−11 GeV−1. Complementary methods, including Doppler shift measurements of the signal photon lines and dark matter decay searches near the Milky Way's center using the Subaru telescope’s infrared camera and spectrograph, were also presented.4
Recent Observational Studies and Findings
A paper recently published in Physical Review Letters reported the first dark matter search using a high-dispersion spectrograph, WINERED, at the 6.5m Magellan Clay telescope to detect photons from dark matter decays.5
The team studied ALPs and their potential to emit light in the NIR spectrum. Yet, this region is challenging to observe due to interference from various sources like the dim sunlight scattered by interstellar dust, zodiacal light, and light emitted by sun-heated atmosphere.5
In their previous work, the researchers proposed a technique to address the challenge of background radiation. They leveraged the fact that while background radiation spans a wide range of wavelengths, light from specific decay processes is concentrated in a narrow range, allowing for sharper, more focused detection of these events.5
The dwarf spheroidal galaxies (dSphs) Tucana II and Leo V were observed using an object-sky-object nodding technique. Using zero consistent flux data after the sky subtraction and conducting Doppler shift analysis for additional background subtraction, the study established one of the strictest limits on dark matter lifetime in the mass range of 1.8–2.7 eV.5
The conservative bound for ALPs was translated to the photon coupling gϕγγ ≲ (2–3) × 10−11 GeV−1 (10−10 GeV−1) for ultra-faint dSphs with a Navarro-Frenk-White dark matter profile. Precise infrared measurements established new limitations on the dark matter lifetime with just four hours of observations, suggesting lifetimes between 1025 to 1026 seconds. The light observed in the near infrared was accurately accounted for using the WINERED technique, allowing for precise statistical analysis. Then, the absence of decay events was used to establish a lower bound on the ALP particle lifespan.5
In another recent paper published in Physical Review Letters, researchers searched for a narrow emission line from decaying dark matter using public blank sky observations obtained from the NIRSpec IFU on the JWST. They derived leading constraints on the axion-photon coupling for ALPs in the 0.8–3 eV mass range. These results did not rely on dedicated observations, and the reach could automatically improve as JWST continues its observations.6
Technological Advancements Facilitating Research
The high spectral and angular resolution capabilities of instruments like WINERED and NIRSpec enable the potential identification of monochromatic photon emissions associated with dark matter decay, through effective background noise suppression.5,7
WINERED is a high-resolution NIR spectrograph developed by the University of Tokyo and Kyoto Sangyo University. Initially operated with the 3.58 m New Technology Telescope, this PI-type instrument was later fitted to the 6.5 m Magellan Clay telescope. WINERED offers exceptional sensitivity with an instrumental throughput of up to 50%, making it suitable for telescopes ranging from 3-4 m class to 8-10 m class, particularly in the short NIR spectrum (0.9-1.35 µm).5
The NIRSpec operates between 0.6 to 5 microns, dispersing light into a spectrum to analyze an object's physical properties like temperature and chemical composition. By identifying spectral lines, it reveals detailed information about chemical elements and physical conditions. To study thousands of faint galaxies during its 5-year mission, NIRSpec can observe 100 objects simultaneously, a groundbreaking feature enabled by a new microshutter system. This makes NIRSpec the first space-based spectrograph with this multi-object capability.7
Future Prospects and Ongoing Missions
Future space missions are poised to expand the understanding of the dark universe, with European Space Agency (ESA)'s Euclid mission mapping dark energy and matter, and National Aeronautics and Space Administration (NASA)'s Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer (SPHEREx) mission exploring the NIR spectrum to uncover more about dark matter's distribution and properties.8,9
Launched on 1 July 2023, ESA's Euclid mission aims to study the evolution and composition of the dark universe. It will create a map of the universe’s large-scale structure across space and time by observing billions of galaxies up to 10 billion light-years away, covering more than a third of the sky to investigate the expansion of the universe and the formation of cosmic structures.8 The SPHEREx mission, scheduled for launch in March 2025, will conduct an all-sky spectral survey over two years, collecting data on over 450 million galaxies and 100 million stars in the Milky Way. Its goal is to investigate the origins of the universe.9
Conclusion
The use of NIR spectroscopy in dark matter research holds great promise, with advanced instruments like NIRSpec and WINERED providing crucial insights into the properties of dark matter. Ongoing and future missions, such as Euclid and SPHEREx, will further improve our understanding of dark matter. These technological advancements may soon lead to breakthroughs in detecting and characterizing dark matter, ultimately unveiling the mysteries of the cosmos.
References and Further Reading
- Shen, T. (2024). Overview of dark matter detection. Theoretical and Natural Science, 43, 184-189. DOI: 10.54254/2753-8818/43/20240819, https://www.ewadirect.com/proceedings/tns/article/view/14169
- Misiaszek, M., Rossi, N. (2024). Direct Detection of Dark Matter: A Critical Review. Symmetry, 16(2), 201. DOI: 10.3390/sym16020201, https://www.mdpi.com/2073-8994/16/2/201
- Pérez de los Heros, C. (2020). Status, challenges and directions in indirect dark matter searches. Symmetry, 12(10), 1648. DOI: 10.3390/sym12101648, https://www.mdpi.com/2073-8994/12/10/1648
- Bessho, T., Ikeda, Y., Yin, W. (2022). Indirect detection of eV dark matter via infrared spectroscopy. Physical Review D, 106(9), 095025. DOI: 10.1103/PhysRevD.106.095025, https://journals.aps.org/prd/abstract/10.1103/PhysRevD.106.095025
- Yin, W. et al. (2025). First result for dark matter search by WINERED. Physical Review Letters, 134(5), 051004. DOI: 10.1103/PhysRevLett.134.051004, https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.134.051004
- Janish, R., Pinetti, E. (2025). Hunting dark matter lines in the infrared background with the James Webb Space Telescope. Physical Review Letters, 134(7), 071002. DOI: 10.1103/PhysRevLett.134.071002, https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.134.071002
- Near InfraRed Spectrograph (NIRSpec) [Online] Available at https://science.nasa.gov/mission/webb/nirspec/ (Accessed on 07 March 2025)
- Euclid [Online] Available at https://www.esa.int/Science_Exploration/Space_Science/Euclid (Accessed on 07 March 2025)
- SPHEREx [Online] Available at https://science.nasa.gov/mission/spherex/ (Accessed on 07 March 2025)
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