DESI’s 3D universe map reveals 47 million galaxies spanning Milky Way to ‘cosmic noon’ – Live Science

Cosmic Web Mapping: DESI’s 3D Universe Map Reveals 47 Million Galaxies

The Dark Energy Spectroscopic Instrument (DESI) project has created a three-dimensional map of over 47 million galaxies, spanning from the Milky Way to the era known as ‘cosmic noon’. This period, approximately 10 billion years ago, marked the peak of cosmic activity when star formation rates were 10–100 times higher than today. Quasars, luminous cores powered by supermassive black holes, were most common during this time, serving as key markers for studying the early universe. The term ‘cosmic noon’ signifies the peak of galactic and large-scale structure development.

The Cosmic Web: Structure and Evolution

The DESI map visualizes the universe as a vast ‘cosmic web‘ of galaxy filaments interspersed with voids. This structure, shaped by gravitational interactions, reveals how matter has aggregated over billions of years. The map includes data on 34 million galaxies and quasars, alongside over 20 million nearby stars within the Milky Way. Light from these objects, some traveling billions of years to reach Earth, allows scientists to trace the universe’s evolutionary history. The web-like structure provides a record of how galaxies have shifted and clustered over time.

Dark Energy and Cosmic Expansion

Dark energy, comprising roughly 70% of the universe, drives its accelerated expansion. The DESI map aids in studying this force by analyzing changes in galaxy distributions across cosmic history. Preliminary data suggests dark energy may not be constant, challenging the cosmological constant model. Instead, it implies dark energy’s density could evolve, potentially requiring revisions to the Standard Model of Cosmology. Researchers compare galaxy clustering at different epochs to assess dark energy’s influence over the past 11 billion years.

Quasars and Cosmic Ray Insights

During cosmic noon, quasars—powered by supermassive black holes—were abundant, acting as luminous markers across the cosmos. These quasars offer critical insights into the intergalactic medium and the coevolution of galaxies with their central black holes. Recent studies, including an analysis of radio spectral energy distributions (SEDs) of 160 galaxies led by Fatemeh Tabatabaei, indicate cosmic ray electrons were more energetic in this era. This suggests turbulent magnetic fields may have accelerated cosmic rays, allowing them to decouple from fields. The infrared–radio correlation (IRRC) remains consistent with redshift, despite evolving radio SEDs, underscoring the value of radio observations in studying star formation at high redshifts.

DESI’s Observations and Future Goals

DESI’s observations will continue through 2028, expanding the map by 20% and targeting fainter, more distant galaxies. Future studies will focus on regions near the Milky Way, where stellar interference has limited observations, and the southern sky, requiring the telescope to peer through more of Earth’s atmosphere. The first results from the full dataset are expected in 2027, promising deeper insights into dark energy’s behavior and the universe’s fate. As the map grows, it will refine existing cosmological models, addressing tensions in current theories and potentially revealing new phenomena that could redefine understanding of the cosmos.

Uncertainties and Ongoing Research

Despite the DESI map‘s groundbreaking data, uncertainties persist. The exact nature of dark energy and its potential evolution over time remain poorly understood. Some researchers argue observed variations in dark energy’s density could result from measurement errors or incomplete data rather than intrinsic properties of dark energy. Additionally, the relationship between supermassive black holes and galaxy formation during cosmic noon is debated. While some studies suggest a direct link, others highlight the complexity of feedback mechanisms regulating star formation. These uncertainties emphasize the need for ongoing observation and theoretical refinement to distinguish between competing models of cosmic evolution.

The DESI map represents a major milestone in astrophysics, offering a detailed snapshot of the universe’s structure and evolution. By capturing light from galaxies across cosmic time, it provides a unique perspective on the forces shaping the cosmos. As researchers analyze this data, the map may uncover new truths about dark energy, galaxy formation, and the universe’s ultimate destiny. This achievement underscores the power of collaborative science in unraveling the mysteries of the cosmos.