StarTalk• Mar 24, 2026• 51:27Interview

How We’re Trying to Detect Dark Matter Particles, with Katherine Freese

From StarTalk

Katherine Freese•Director of the Weinberg Institute for Theoretical Physics, UT Austin

Executive Summary

The James Webb Space Telescope (JWST) is challenging existing cosmological models by discovering unexpectedly mature galaxies in the early universe.
A theoretical object called a "dark star"—made of ordinary matter but powered by dark matter annihilation—may explain these early galaxies and the formation of supermassive black holes, with JWST having already identified potential candidates.
New experimental approaches for detecting dark matter, such as "paleo detectors" that search for particle tracks in ancient rocks, are being developed as conventional liquid xenon experiments have yet to yield a discovery.
Recent data from the Dark Energy Spectroscopic Instrument (DESI) has sparked debate about whether dark energy is constant or changes over time, a question with profound implications for the fate of the universe.

10 quotes

Concerns Raised

Current dark matter detection experiments using liquid xenon have not yet found a conclusive signal.
The standard cosmological model is being challenged by JWST's observations of unexpectedly mature early galaxies.
The theoretical value for vacuum energy is a staggering 120 orders of magnitude larger than the observed value of dark energy, representing a major crisis in physics.

Opportunities Identified

JWST data may provide the first observational evidence for theoretical objects like "dark stars."
Novel experiments like "paleo detectors" offer a new, complementary method for searching for dark matter interactions.
Data from experiments like DESI could reveal if dark energy is evolving, which would revolutionize our understanding of cosmology.
The search for purely dark matter galaxies via gravitational lensing could provide direct evidence of large-scale dark matter structures.

Key Themes

The 'Dark Star' Hypothesis

Physicist Katie Freese discusses her theory of "dark stars," the universe's first stars, which are composed of ordinary matter but powered by dark matter annihilation instead of nuclear fusion. These stars could grow to be a million times more massive and a billion times brighter than the sun, and the JWST has found candidate objects that fit this profile.

The existence of dark stars could solve two major cosmological puzzles: the origin of supermassive black holes in the early universe and the presence of surprisingly developed galaxies observed by JWST.

Innovative Dark Matter Detection

The discussion highlights the limitations of current dark matter searches, which primarily use large vats of liquid xenon. A novel proposed method, "paleo detectors," would search for the faint tracks left by dark matter particles interacting with ancient minerals over geological timescales, offering a new window into the particle's properties.

As conventional experiments have so far failed to detect dark matter, innovative and complementary approaches like paleo detectors are crucial for making progress in identifying this elusive substance that constitutes most of the universe's mass.

JWST's Impact on Early Universe Cosmology

The James Webb Space Telescope's observations are providing a stream of surprising data about the early universe. It has found galaxies that appear far more massive and developed than predicted by the standard model of cosmology, forcing theorists to reconsider models of galaxy and structure formation.

This new data is creating a productive crisis in cosmology, potentially pointing towards new physics or phenomena, such as dark stars, that accelerated the formation of cosmic structures.

The Evolving Mystery of Dark Energy

The episode touches on the ongoing debate about the nature of dark energy, the force driving the universe's accelerated expansion. Recent results from the DESI experiment suggest dark energy might not be a cosmological constant but could be evolving, though follow-up analysis by Freese and others has not found strong evidence for this yet.

Determining whether dark energy is constant or dynamic is one of the most important goals in modern physics, as it dictates the ultimate fate of the universe and could point to new fundamental theories, such as those involving extra dimensions.

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Topics

Cosmology Dark Matter Dark Energy Dark Stars James Webb Space Telescope (JWST)Paleo Detectors WIMPs Supermassive Black Holes Early Universe Galaxy Formation String Theory Brane Cosmology Gravitational Lensing DESI (Dark Energy Spectroscopic Instrument)Liquid Xenon Detectors

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