Hubble telescope spots ‘impossible’ light from a galaxy that shouldn’t have been visible
Astronomers have spotted an ancient galaxy shining through the cosmic fog of the early universe, revealing a detailed view that was thought impossible.
using the NASA‘S Hubble Space Telescopewith data from James Webb Space Telescope (JWST) and the European Southern Observatory’s Very Large Telescope (VLT), researchers detected “ionizing” ultraviolet photons – energetic light capable of stripping electrons from hydrogen atoms – coming from the galaxy, called MXDFz4.4. This is the earliest such detection on record, coming about 250 million years after the end of a major cosmic transition. era of reionizationResearchers reported in a study published on June 23 The Astrophysical Journal.
after hundreds of millions of years big bangThe space between the galaxies was filled with a fog of neutral hydrogen gas that blocked this type of light. Over time, radiation from the first stars and galaxies ionized that gas, allowing the fog to clear and light to travel freely across the universe – a process that astronomers are still working to fully understand.
“It was thought that it was impossible,” Elias Govaerts, a postdoctoral fellow at the Space Telescope Science Institute (STSCI) in Baltimore and first author of the new study, told Live Science. “The really special thing about this galaxy is that it’s passing through such a large part of the intergalactic medium [the ionized plasma between galaxies]. It’s the most distant, so it’s the most intergalactic medium to go through.”
What makes MXDFz4.4 unusual is the combination of its size and star-formation rate. The galaxy is about 100 times smaller in terms of area galaxyYet it forms stars about 10 times faster, packing a large number of massive young stars into a compact space. According to Govaerts, the crowding effect helps the galaxy punch clear channels through the gas surrounding it, allowing ionized light to escape the galaxy and, ultimately, the faint space between galaxies. The team estimates that somewhere between half and all of the galaxy’s ionized light is escaping.
The discovery, made in October, occurred somewhat by chance. While preparing an unrelated funding proposal just days before a key deadline, Govaerts examined an existing, deeper Hubble image to see if anyone had looked for such a signal before. Within a few hours he got a promising signal. “It was pretty quick that I got the idea that OK, there’s something here and it’s exciting,” Govaerts said. “We were excited from day one, but then it took several months to mature and extract all the properties about the galaxy.”
An illustration of the galaxy MXDFz4.4 as it appeared about 1.4 billion years after the Big Bang, as the era of reionization was ending.
(Image credit: NASA, ESA, Leah Hustak (STScI))
The discovery relied on an unusually rich set of observations: an extremely deep Hubble image taken from 40 hours of observations; JWST Imaging at multiple wavelengths is used to characterize the stars and star-formation history of the galaxy; And one of the deepest spectra ever taken from a single piece of sky, collected over nearly six days of observation time with the VLT’s Multi-Unit Spectroscopic Explorer instrument. That spectrum confirmed the galaxy’s distance through its Lyman-alpha emission line – which serves as a “hydrogen fingerprint,” or the glow left by excited hydrogen gas, that astronomers can use to measure cosmic distances and time.
According to the study’s co-author, no other galaxy from this early period had previously shown detectable ionizing light, making MXDFz4.4 one of a kind until now. Mark RafelskiDeputy Chief of Mission for Hubble Space Telescope At STSCI, the statement noted. .
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Researchers say the vigorous star formation bursts seen in MXDFz4.4 may have played a key role in clearing the hydrogen fog of the early universe and that more galaxies like it are still waiting to be found.
Govaerts, I., et al (2026). MXDFz4.4: a LyC emitter 250 Myr after the reionization era and the first examination of Lyα morphology as a tracer of LyC escape at high redshift. The Astrophysical Journal1005(1), 34. https://doi.org/10.3847/1538-4357/ae75b0
