What We Have Learned from NICER About Neutron Star Radii
Abstract
The cores of neutron stars have a combination of density, temperature, and neutron-proton asymmetry that cannot be replicated in laboratories or understood using first-principles quantum chromodynamics. Thus, observations of neutron stars are necessary to understand this regime. In particular, precise and accurate measurements of neutron star radii are highly informative about cold, catalyzed matter at a few times nuclear saturation density. X-ray observations with NASA's Neutron star Interior Composition Explorer (NICER) have yielded radius measurements for a few nonaccreting neutron stars, which have advanced substantially our understanding of dense matter. In this review we discuss the NICER radius measurements and their implications and demonstrate that the systematic errors thus far explored in NICER analyses have at most a minor effect on the inferred radii of neutron stars.
Versions
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BibTeX
@misc{miller2026what,
title = {{What We Have Learned from NICER About Neutron Star Radii}},
author = {M. C. Miller},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.36169},
eprint = {2609.36169},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.36169},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - UNPB
TI - What We Have Learned from NICER About Neutron Star Radii
AU - M. C. Miller
PY - 2026
DA - 2026/09/28
PB - arXiv
DO - 10.48550/arxiv.2609.36169
UR - https://arxiv.org/abs/2609.36169
AB - The cores of neutron stars have a combination of density, temperature, and neutron-proton asymmetry that cannot be replicated in laboratories or understood using first-principles quantum chromodynamics. Thus, observations of neutron stars are necessary to understand this regime. In particular, precise and accurate measurements of neutron star radii are highly informative about cold, catalyzed matter at a few times nuclear saturation density. X-ray observations with NASA's Neutron star Interior Composition Explorer (NICER) have yielded radius measurements for a few nonaccreting neutron stars, which have advanced substantially our understanding of dense matter. In this review we discuss the NICER radius measurements and their implications and demonstrate that the systematic errors thus far explored in NICER analyses have at most a minor effect on the inferred radii of neutron stars.
ER -