Highly ionized neon gas detected at the center of the spiral galaxy Messier 83 by the Mid-Infrared Instrument (MIRI) aboard the NASA/ESA/CSA James Webb Space Telescope could be a telltale signature of an active galactic nucleus, according to a team of astronomers led by Space Telescope Science Institute scientists.
This Webb image shows Messier 83. Image credit: NASA / ESA / CSA / Webb / A. Adamo, Stockholm University / FEAST JWST Team.
Messier 83 is a grand-design barred spiral galaxy located 15 million light-years away in the southern constellation of Hydra.
Also known as the Southern Pinwheel Galaxy, M83, NGC 5236, LEDA 48082 and UGCA 366, the galaxy is about twice as small as the Milky Way.
Messier 83 was discovered by the French astronomer Nicolas Louis de Lacaille on February 17, 1752.
It has an apparent magnitude of 7.5 and is one of the brightest spiral galaxies in the night sky. It can be observed using a pair of binoculars most easily in May.
It is a prominent member of a group of galaxies known as the Centaurus A/M83 Group, which also counts the dusty NGC 5128 (Centaurus A) and the irregular galaxy NGC 5253 as members.
Messier 83 has long been an enigma. While massive spiral galaxies often host active galactic nuclei (AGNs), astronomers have struggled for decades to confirm one in Messier 83.
Previous observations hinted that if a supermassive black hole existed there, it must be dormant or hidden behind thick dust. However, the new Webb observations unveil signs that suggest otherwise.
“Our discovery of highly ionized neon emission in the nucleus of M83 was unexpected,” said Dr. Svea Hernandez, an astronomer with AURA for ESA at the Space Telescope Science Institute.
“These signatures require large amounts of energy to be produced — more than what normal stars can generate.”
“This strongly suggests the presence of an AGN that has been elusive until now.”
“Before Webb, we simply did not have the tools to detect such faint and highly ionised gas signatures in M83’s nucleus.”
“Now, with its incredible mid-infrared sensitivity, we are finally able to explore these hidden depths of the galaxy and uncover what was once invisible.”
Webb’s mid-infrared observations allowed the astronomers to peer through dust and detect the telltale signs of highly ionized gas in small clumps near the galactic nucleus.
The energy needed to create these signatures is significantly higher than what supernovae or other stellar processes can provide, making an AGN the most likely explanation.
However, alternative scenarios, such as extreme shock waves in the interstellar medium, are still being investigated.
“Webb is revolutionising our understanding of galaxies,” said Dr. Linda Smith, an astronomer at the Space Telescope Science Institute.
“For years, astronomers have searched for a black hole in M83 without success. Now, we finally have a compelling clue that suggests one may be present.”
“This discovery showcases how Webb is making unexpected breakthroughs.”
“Astronomers thought they had ruled out an AGN in M83, but now we have fresh evidence that challenges past assumptions and opens new avenues for exploration.”
The findings appear in the Astrophysical Journal.
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Svea Hernandez et al. 2025. JWST/MIRI Detection of [Ne v] and [Ne vi] in M83: Evidence for the Long Sought-after Active Galactic Nucleus? ApJ 983, 154; doi: 10.3847/1538-4357/adba5d
