# ELT Instrument Could Solve Dark Matter Mysteries via Ultra-Diffuse Galaxies Proposed NEXUS@SHARP instrument aims to decode galaxy formation and dark matter models. - **Source:** [Universe Today](https://www.universetoday.com) - **Published:** 2026-11-06 - **Topic:** [science](https://brifing.si/c/science) - **Original article:** - **On Brifing:** https://brifing.si/s/c2ed53b4-3a76-4dda-9063-7af24dde5850 ## The ELT's Scientific Potential The Extremely Large Telescope, scheduled for first light in March 2029, aims to address fundamental cosmological questions. One primary objective involves investigating dark matter within the Lambda-CDM framework. Researchers propose a new instrument, NEXUS@SHARP, to observe ultra-diffuse galaxies, which currently challenge existing models of galaxy formation and dark matter distribution. ## Understanding Ultra-Diffuse Galaxies Ultra-diffuse galaxies are as large as the Milky Way but contain significantly fewer stars, making them extremely faint. Their existence contradicts standard galaxy formation models, as their diffuse nature is difficult to reconcile with expected dark matter halo sizes. Astronomers currently lack the spectroscopic depth required to fully characterize these systems. ## NEXUS@SHARP Instrument Capabilities NEXUS@SHARP is a proposed near-infrared multi-slit spectrograph designed for the ELT. It combines high spatial resolution with efficient multiplexing, allowing astronomers to observe multiple globular clusters simultaneously. This capability significantly reduces the telescope time required to gather data from faint systems located up to 70 megaparsecs away from Earth. ## Globular Clusters as Tracers Globular clusters serve as vital tracers for probing the dark matter halos surrounding ultra-diffuse galaxies. Because these clusters are brighter and extend further outward than their host galaxies, they provide essential data for measuring mass. Analyzing their spectra reveals formation histories, including stellar ages and metallicities, which indicate how galaxies evolved. ## Testing Formation Scenarios Researchers are evaluating two primary formation scenarios for ultra-diffuse galaxies. One suggests they are failed massive galaxies that quenched early, while the other posits they are puffed-up dwarf galaxies. NEXUS@SHARP will provide the precise radial velocities and stellar population data needed to distinguish between these competing theories of galaxy development. ## Dual Mass Measurement Method The instrument will enable two independent mass measurements for each galaxy. The first is dynamical mass, derived from the velocity dispersion of globular clusters. The second is GC-count mass, based on the correlation between cluster numbers and halo mass. Comparing these two metrics helps determine if a galaxy's halo is overmassive. ## Implications for Lambda-CDM The Lambda-CDM model remains the leading cosmological framework, yet it fails to explain certain observations regarding dark matter. By providing high-quality data on ultra-diffuse galaxies, NEXUS@SHARP could either confirm or contradict current predictions. This research is essential for refining our understanding of the fundamental structural units of the universe. ## Future Observational Prospects While NEXUS@SHARP is currently a concept, its potential to conduct systematic spectroscopic surveys is significant. If constructed, it will act as a definitive tool for constraining the formation channels of elusive galaxy populations. This effort represents an ongoing, multi-directional approach to solving the enduring mysteries of dark matter and energy. ## Sources covering this story - https://www.universetoday.com/articles/the-elt-can-probe-ultra-diffuse-galaxies-and-their-dark-matter-mysteries — --- _Summary written by Brifing from the original reporting. Copyright in the original article belongs to its publisher; read the full piece at the link above._