Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have identified “Shadow Blaster,” a dust-obscured galaxy from 11 billion years ago, as the most plausible counterpart to the high-energy neutrino event IC 210922A. Detected by the IceCube Neutrino Observatory in 2021, the 750 teraelectronvolt neutrino lacked an obvious origin until researchers utilized gravitational lensing to resolve the distant, compact starburst galaxy. According to the study published in Nature Astronomy by Y. Urata et al., the galaxy’s dense, gas-rich core and position within the neutrino’s localization region suggest that similar compact starbursts may contribute significantly to the high-energy neutrino background.
How does gravitational lensing reveal hidden galaxies?
Gravitational lensing acts as a natural cosmic telescope, allowing researchers to study objects that would otherwise be too faint or distant to resolve. In the case of JCMT0402−0424, nicknamed Shadow Blaster, the gravity of a massive foreground galaxy bends and magnifies light from the background source. According to the research team, this process split the light into four distinct images, enabling ALMA to capture spatial scales within the galaxy that were previously inaccessible. By modeling these distortions, astronomers reconstructed the galaxy’s intrinsic structure, revealing an extended star-forming region of roughly 1,700 light-years alongside a highly compact core.
What is the connection between Shadow Blaster and IceCube?
On September 22, 2021, the IceCube Neutrino Observatory recorded IC 210922A, a neutrino with an energy level of approximately 750 teraelectronvolts. While typical astronomical events rarely produce such energy, the localization region remained largely empty during initial optical and X-ray surveys. Follow-up observations using the James Clerk Maxwell Telescope and the Submillimeter Array eventually identified Shadow Blaster. According to the study, the statistical probability of finding such a bright submillimeter galaxy at random within that specific region is 1% or lower, making it the leading candidate for the neutrino’s source.
Could compact starburst galaxies explain the neutrino background?
The discovery of Shadow Blaster provides new evidence that “Cosmic Noon” galaxies—those existing roughly 11 billion years ago—may be responsible for a portion of the diffuse astrophysical neutrino flux. Population modeling by Urata et al. suggests that compact-core dusty starburst galaxies could account for between 15% and 20% of the neutrinos detected by IceCube in the teraelectronvolt to petaelectronvolt range. While this confirms these galaxies are not the sole source of all high-energy neutrinos, it positions them as a meaningful contributor to the cosmic background.
Frequently Asked Questions
- What is a high-energy neutrino? It is a nearly massless subatomic particle that travels through the universe at nearly the speed of light, carrying information about the most violent events in space.
- Why was Shadow Blaster hard to find? The galaxy is heavily obscured by thick clouds of interstellar dust, making it nearly invisible to traditional optical telescopes.
- Is the link between the galaxy and the neutrino confirmed? No. While Shadow Blaster is the most plausible candidate due to its rare properties and location, researchers acknowledge that a chance alignment cannot be ruled out.
- What is ALMA? The Atacama Large Millimeter/submillimeter Array is an international astronomy facility located in Chile, designed to observe the universe at millimeter and submillimeter wavelengths.
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