JWST discovers a new barred spiral galaxy
An international team of astronomers reports the discovery of a new massive barred spiral galaxy. The newfound galaxy, designated M1149-BSG-z5, was identified using the James Webb Space Telescope (JWST). The finding was detailed in a paper published June 23 on the preprint server arXiv.
The bars are out there
For astronomers, bars are important structures in galaxies, highly related to galaxy secular evolution. Although bars are common in nearby disk galaxies, at high redshifts, the cosmic environment is drastically different from the local universe, and bar structure formation is expected to be suppressed.
One of the tools that has helped uncover many of these high-redshift barred galaxies is JWST. Observations with this space telescope have found that barred galaxies emerge as early as a redshift of about 4.0, with observed fractions of 3–7% at a redshift of 3.5.
New barred galaxy at the Epoch of Reionization
Now, a group of astronomers led by Xiaohan Wang of Tsinghua University in Beijing adds a new galaxy to this list.
"M1149-BSG-z5 was identified in the NIRISS (Near-Infrared Imager and Slitless Spectrograph) imaging parallel field of JWST Cycle-2 program 'Medium-band Astrophysics with the Grism of NIRCam in Frontier Fields,'" the researchers wrote in the paper.
The newfound galaxy M1149-BSG-z5 has a redshift of 5.1 and hosts a stellar bar with a length of approximately 14,700 light-years. This makes it the highest-redshift barred galaxy known to date.
The properties of M1149-BSG-z5
According to the study, M1149-BSG-z5 has an effective radius of about 8,500 light-years, and its spiral arms extend to a radius of some 17,900 light-years. The mass of the galaxy was estimated to be 28 billion solar masses, and its star-formation rate was found to be at a level of 144 solar masses per year.
Furthermore, the study found that M1149-BSG-z5 hosts an active galactic nucleus (AGN), with a relatively low black-hole-to-stellar mass ratio of about 0.001. This is lower than those of many high-redshift AGNs and comparable to local AGNs.
The astronomers conclude that the properties of M1149-BSG-z5, together with its high metallicity (about 50% solar) and its location on the BPT (Baldwin, Phillips, and Terlevich) diagram, which is used to determine whether a galaxy's gas is being ionized by intense star formation or by an active, supermassive black hole, make it a high-redshift massive, chemically evolved galaxy.
When compared with other galaxies, M1149-BSG-z5 turns out to be larger than typical galaxies at a redshift of about 5.0 and comparable to barred galaxies with redshifts between 2.0 and 4.0. The authors of the paper note that the nearest galaxy to M1149-BSG-z5 is about 69,000 light-years away, which suggests that interaction may play a role in the bar formation of the newly detected system.
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Publication details
Xiaohan Wang et al, A massive barred spiral galaxy at z = 5.102 discovered by JWST, arXiv (2026). DOI: 10.48550/arxiv.2606.25022
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Citation: JWST discovers a new barred spiral galaxy (2026, July 3) retrieved 17 July 2026 from https://phys.org/news/2026-07-jwst-barred-spiral-galaxy.html
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