SN 1987A is the closest supernova observed since the moment of explosion and the only one where the compact remnant has not yet been directly detected. The first JWST observations in 2022 revealed narrow argon and sulfur lines from the center, providing strong evidence for ionization by a compact object. This work fits into the broader study of supernova remnants and compact objects, alongside studies of dust, rings, and X-ray emission. However, the nature of the object, whether a neutron star or a black hole, remained an open question, and the properties of dust in the inner ejecta were poorly constrained.
Spectroscopic observations with JWST/NIRSpec (high resolution, 0.92–5.27 μm) and MIRI/MRS (4.9–27.9 μm) were used at epochs 13,500 and 13,300 days after the explosion. For each line, maps and velocity profiles were constructed, and the continuum and diffuse background were subtracted. The spatial resolution of NIRSpec allowed the compact source to be separated from the extended ring emission. Photoionization models for a pulsar wind nebula and a cooling neutron star were compared with the measured line luminosities, accounting for dust absorption and scattering.
The narrow lines [Ar VI], [Ar II], [S IV], and [S III] are confirmed, and [Ca V], [Cl II], and possibly [Fe II] are identified for the first time. All lines show a blueshift of about −250 km/s and originate from an unresolved region southeast of the center. The offset and Doppler shift give a neutron star kick velocity of 510±55 km/s. The [Ca IV] line is unusual: it is shifted to the north and has a redshift of ~700 km/s. Modeling shows that scattering by dust grains of size ~0.3 μm explains the properties of [Ca IV] and the absence of other narrow lines at short wavelengths, while dust absorption is important at λ ≳ 8 μm. Both photoionization models agree with the observations, except for the [Fe II] line, which is strongly underpredicted.
This work refines the picture of ionization in the inner ejecta and places constraints on dust properties. Unlike neighboring studies, where dust was mainly studied through thermal emission, here it manifests through its effect on emission lines, providing an independent estimate of grain size. This is the first quantitative test of the dust scattering scenario to explain line anomalies in SN 1987A.
As the ejecta expand, the optical depth of dust will decrease as t⁻², revealing new lines at short wavelengths. The difference between the pulsar wind nebula and cooling neutron star models will appear in the emergence of the [S III] 0.9533 μm, [C I] 0.9827/0.9853 μm, and [Si VI] 1.9646 μm lines. Monitoring the center in the coming years will allow us to choose the correct scenario.
The results will affect our understanding of the connection between supernova progenitor properties and the compact objects they produce, as well as models of dust formation in supernovae.
Continue monitoring the narrow lines with JWST to test temporal evolution and confirm the [Fe II] line. Refine dust models to account for the grain size distribution and composition.
An unresolved question in the astrophysics of compact objects is how often neutron stars are born with pulsar wind nebulae and how explosion properties determine the kick velocity. SN 1987A is a unique case where these parameters can be measured directly.
This section is addressed to the author of the paper and their colleagues. Neighbouring works were found by meaning-based search across our archive, not by word overlap. We do not review: we show the field around the work.
What the work does
The study uses new spectroscopic observations from JWST/NIRSpec and MIRI/MRS to analyze narrow emission lines from the center of SN 1987A. It confirms lines of [Ar VI], [Ar II], [S IV], [S III], and for the first time identifies [Ca V], [Cl II], and possibly [Fe II]; all lines are blueshifted and originate from a region southeast of the center. Modeling shows that scattering by dust with grain sizes of ~0.3 μm explains the [Ca IV] anomalies and the absence of short-wavelength lines, while both photoionization models (pulsar wind nebula and cooling neutron star) are consistent with the observations.
Where its strength is
This work provides an independent estimate of dust grain sizes based on their effect on emission lines, rather than on thermal emission, and for the first time quantitatively tests the dust-scattering scenario to explain line anomalies in SN 1987A.
Where it could go next
Worth trying
Why this may matter
Refining the properties of dust and the nature of the compact object in SN 1987A is important for understanding supernova evolution and the formation of neutron stars and black holes, as well as for interpreting future JWST observations.
Nearby works in our archive
The archive is sparse around this work: the closest review is only 0.58, against a usual 0.64. It looks like few have drilled nearby.
The neutron star kick velocity in SN 1987A (510 km/s) is 15 times the speed of Earth's orbit around the Sun. In one second, such a star would travel the distance from Moscow to Saint Petersburg.