Discovery of thionylimide, HNSO, in space: the first N-, S- and O-bearing interstellar molecule
Pith reviewed 2026-05-24 02:31 UTC · model grok-4.3
The pith
Thionylimide (HNSO) is detected for the first time in interstellar space as the initial molecule containing N, S and O together.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
The central claim is the first detection in space of thionylimide (HNSO) toward G+0.693-0.027. This molecule is the first species detected in the interstellar medium containing simultaneously N, S and O. Numerous Ka = 0, 1 and 2 transitions belonging to HNSO covering Jup = 2 to 10 are identified, including several completely unblended features. A molecular column density of (8 ± 1)×10^{13} cm^{-2} is derived, yielding a fractional abundance relative to H2 of ~6×10^{-10}. HNSO is likely formed through the reaction of the NSO radical and atomic H on the surface of icy grains.
What carries the argument
Assignment of multiple unblended Ka = 0, 1 and 2 rotational transitions of HNSO spanning Jup = 2 to 10 in the line survey data.
If this is right
- HNSO acts as a link between N-, S- and O-bearing interstellar chemistry.
- The detection opens routes to searching for a new family of NSO-bearing molecules.
- Grain-surface chemistry involving NSO + H is a viable formation path for such species.
- The measured abundance places HNSO as a minor component relative to SO and SO2.
Where Pith is reading between the lines
- Targeted searches for HNSO in other high-density clouds could reveal whether this chemistry operates beyond the Galactic Center.
- Detection of related NSO radicals or larger analogs would test the proposed grain-surface route.
- Updated chemical models incorporating HNSO may alter predicted sulfur budgets in dense gas.
Load-bearing premise
The observed lines are produced by HNSO and are not significantly contaminated by lines from other species.
What would settle it
Laboratory spectra showing that HNSO does not emit at the observed frequencies with the reported intensities would disprove the identification.
Figures
read the original abstract
We present the first detection in space of thionylimide (HNSO) toward the Galactic Center molecular cloud G+0.693-0.027, thanks to the superb sensitivity of an ultradeep molecular line survey carried out with the Yebes 40$\,$m and IRAM 30$\,$m telescopes. This molecule is the first species detected in the interstellar medium containing, simultaneously, N, S and O. We have identified numerous $K$$_a$ = 0, 1 and 2 transitions belonging to HNSO covering from $J$$_{\rm up}$ = 2 to $J$$_{\rm up}$ = 10, including several completely unblended features. We derive a molecular column density of $N$ = (8 $\pm$ 1)$\times$10$^{13}$ cm$^{-2}$, yielding a fractional abundance relative to H$_2$ of $\sim$6$\times$10$^{-10}$, which is about $\sim$37 and $\sim$4.8 times less abundant than SO and SO2, respectively. Although there are still many unknowns in the interstellar chemistry of NSO-bearing molecules, we propose that HNSO is likely formed through the reaction of the NSO radical and atomic H on the surface of icy grains, with alternative routes also deserving exploration. Finally, HNSO appears as a promising link between N- , S- and O- interstellar chemistry and its discovery paves the route to the detection of a new family of molecules in space.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript reports the first detection of thionylimide (HNSO) in space toward the Galactic Center molecular cloud G+0.693-0.027. This is presented as the first interstellar molecule containing N, S, and O simultaneously. Identification relies on numerous Ka=0,1,2 transitions (J_up from 2 to 10) observed with Yebes 40m and IRAM 30m telescopes, including several unblended lines. A column density of (8 ± 1)×10^{13} cm^{-2} is derived, corresponding to a fractional abundance of ~6×10^{-10} relative to H_2. Formation on icy grains via NSO + H is proposed.
Significance. If the line identification holds, the result is significant because it supplies the first direct observational link between N-, S-, and O-bearing interstellar chemistry and indicates a new family of molecules worth searching for. The evidentiary basis—multiple Ka ladders with several completely unblended features—matches the standard used for prior new-molecule detections and is not undermined by circular fitting or parameter reduction.
Simulated Author's Rebuttal
We thank the referee for their positive assessment of our manuscript and for recommending acceptance. We are pleased that the detection and its significance are viewed as meeting the standards for new interstellar molecule identifications.
Circularity Check
No significant circularity
full rationale
The paper reports a direct observational detection of HNSO through identification of multiple Ka=0,1,2 transitions (Jup=2-10) in Yebes 40m and IRAM 30m spectra toward G+0.693-0.027, with several unblended lines. Column density N=(8±1)×10^13 cm^-2 is obtained via standard LTE line fitting to the observed intensities; fractional abundance is then computed relative to independently measured H2. No derivation reduces by the paper's own equations to a fitted input, no self-citation chain is load-bearing for the detection claim, and no ansatz or uniqueness theorem is invoked. The result is self-contained against external spectral catalogs and prior molecule detections.
Axiom & Free-Parameter Ledger
free parameters (1)
- molecular column density N =
(8 ± 1)×10^13 cm^{-2}
axioms (1)
- domain assumption Observed spectral features match laboratory frequencies of HNSO and arise predominantly from this species without major blending
Reference graph
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