Using the James Webb Space Telescope, researchers have detected a mysterious, unidentified emission signal in deep space that appeared twice in observations from August and November 2023, leaving astronomers without an explanation for its origin. Led by University of Minnesota astrophysicist Mason Huberty, the team published their findings in The Astrophysical Journal, detailing how the signal emerged from a patch of space in the southern constellation Fornax where earlier observations by both the Hubble Space Telescope and James Webb showed no visible object.
Unexplained Signal Baffles Astronomers
The unusual detection surfaced within the Hubble Ultra Deep Field, a heavily studied region of the sky containing nearly 10,000 galaxies extending billions of light-years into the universe. While the Hubble Space Telescope spent more than 270 hours surveying the area, and earlier James Webb observations including an October 2022 JADES survey recorded nothing at the specific location, the recent targeted observations revealed a single bright emission line at a wavelength of approximately 1.6 micrometers. Researchers successfully ruled out instrument error because the signal appeared across four sets of combined exposures taken at different angles and 88 days apart.
Investigating the Empty Void
To uncover previously hidden celestial objects, the research team utilized the Near Infrared Spectrograph (NIRSpec) instrument rather than pointing only at known targets. By opening the instrument’s tiny shutters and blocking out interfering foreground objects, the team gathered seven total detections. Six of those signals matched galaxies already recorded in the Hubble Ultra Deep Field, but the seventh detection stood apart as a solitary near-infrared emission line unaccompanied by additional spectral lines.
The absence of accompanying spectral lines makes the signal extremely difficult to identify without knowing its precise distance from Earth. Calculating that distance requires determining the source’s redshift, which remains impossible with only a single emission line. Because the signal is bright enough that it should have appeared in earlier data like the October 2022 survey, scientists suspect the phenomenon may not have been present at that time, pointing either to a brief powerful flare from an extremely dim object or an unobserved transient event.
Hypotheses and Future Observations
The research team outlined four primary hypotheses to explain the mysterious emission, though none provide a fully satisfactory explanation for the data. The possibilities include a galaxy originating in the early universe, a younger galaxy, a supernova, or a black hole tearing apart a star. However, each theory presents contradictions:
- An early universe galaxy would struggle to send light through the neutral hydrogen that filled the early cosmos and should have appeared in prior imaging.
- A black hole devouring a star can produce a strong emission line without much accompanying light, but current evidence remains insufficient for confirmation.
Concluding their study in The Astrophysical Journal, the team emphasized that follow-up observations are essential to confirm the redshift and determine the physical origin of the emission.
Researchers maintain that deeper and more sensitive spectroscopy will be required to locate potential additional emission lines and definitively establish the true nature of the source.