New Study Reveals How NASA’s Roman Space Telescope Will Uncover Hidden Neutron Stars Across the Galaxy
A new astrophysical study demonstrates that the Roman Space Telescope - scheduled for launch in Sept. 2026 - will open a powerful new window into one of the Universe’s most elusive objects: isolated neutron stars. In their research paper “Astrometric microlensing probes of the isolated neutron star population with Roman” , lead author Zofia Kaczmarek from the Centre for Astronomy of Heidelberg University and colleagues present detailed simulations showing how Roman’s unprecedented precision will enable the discovery and measurement of hundreds of neutron stars that have, until now, remained largely undetectable. Such neutron stars could provide valuable answers to fundamental questions about stellar evolution and the physics of supernova explosions.
Neutron stars, the ultra-dense remnants of massive stellar explosions, are difficult to detect unless they emit radiation as pulsars or exist in binary systems. However, most neutron stars are assumed to be isolated and effectively invisible.
To overcome this problem, the new study highlights astrometric microlensing as a breakthrough technique. This effect occurs when a neutron star passes in front of a distant background star, its gravity subtly bends and shifts its light on its path to earth. This lets the stars' brightness rise and its position apparently shift. Roman - as this space telescope's name is abbreviated - will be the first mission capable of routinely detecting both the brightness change and the tiny positional shift of a microlensed background star, allowing astronomers to directly measure the mass of otherwise invisible objects.
Roman’s Expected Discovery Power
The simulations run by Zofia Kaczmarek and colleagues predict that Roman’s planned "Galactic Bulge Time Domain Survey" will detect about 11,000 microlensing events with both photometric and astrometric signals, 100 events caused by neutron stars, and about 2,500 compact objects in total, including white dwarfs and black holes. "This represents an unprecedented census of dark stellar remnants, enabling population-level studies that were previously impossible", the young scientist enthusiastically explains.
Kaczmarek, PhD student of the Heidelberg microlensing expert Prof. Dr. Joachim Wambsganss, identified a distinctive feature described as a “spur” in observable parameter space, that is unique to neutron stars. This signature allows researchers to efficiently distinguish neutron stars from other lensing objects. The authors emphasize that this method overcomes a long-standing limitation, i.e. that photometric data alone cannot reliably separate neutron stars from more common stellar lenses.
Insights into Stellar Explosions and Extreme Physics
Beyond their detection, Roman’s measurements will provide critical insights into fundamental physics, i.e. the neutron star masses and distributions, the debated “mass gap” between neutron stars and black holes, and the physics of supernova explosions, particularly “natal kicks” that launch neutron stars at high velocities. The study especially shows that observable microlensing patterns depend strongly on these kick velocities, offering a new way to test competing theoretical models.
A New Era of Dark Object Astronomy to begin
To support future discoveries, the research team has created realistic simulated datasets of microlensing events and made these datasets publicly available for the scientific community. The team also developed classification tools to identify neutron star candidates in upcoming data. But this work by Zofia Kaczmarek and colleague scientists also shows that Roman will not only detect isolated and quiescent – or literally, dark – neutron stars. It will also allow us to study them statistically for the first time.
Finally, is no doubt that with its ability to directly measure the masses of invisible objects, the Roman Space Telescope is poised to transform our understanding of the Milky Way’s hidden population. Let's look forward to a time of exciting new discoveries.
ORIGINAL PUBLICATION
Astrometric microlensing probes of the isolated neutron star population with Roman, Kaczmarek, Z. et al., Astronomy & Astrophysics, 707, A264, 2026, http://aanda.org/10.1051/0004-6361/202558238
RELATED PRESS RELEASES
https://www.aanda.org/2026-press-releases
https://www.stsci.edu/contents/news-releases/2026/news-2026-202
https://www.nasa.gov/missions/roman-space-telescope/nasas-roman-poised-to-transform-hunt-for-elusive-neutron-stars/
https://www.llnl.gov/article/54371/nasas-roman-telescope-poised-transform-hunt-elusive-neutron-stars
USEFUL LINKS
Roman Space Telescope (https://roman.gsfc.nasa.gov/)
Centre for Astronomy of Heidelberg University (ZAH) (www.zah.uni-heidelberg.de)
SCIENTIFIC CONTACT
Zofia Kaczmarek
Centre for Astronomy of Heidelberg University (ZAH)
Astronomisches Rechen-Institut (ARI)
zofia.kaczmarek@uni-heidelberg.de
CONTACT FOR MEDIA INQUIRIES
Dr. Guido Thimm
Centre for Astronomy of Heidelberg University (ZAH)
thimm@uni-heidelberg.de
