Phoenix, Arizona – As the NASA spacecraft New Horizons continues its remarkable journey far beyond Earth, the spacecraft’s team has made a surprising and intriguing discovery. After focusing its instruments on a dark area of the sky at the galactic poles for more than 200 hours, the team found that the background light illuminating its path is much brighter than anticipated. This unexpected finding has left scientists puzzled, as they work to unravel the mystery behind this phenomenon.
Launched in January 2006, New Horizons made history by becoming the first spacecraft to explore Pluto up close in 2015. It then went on to study the Kuiper Belt object Arrokoth in 2019, marking the most distant object ever explored by a spacecraft. Despite completing these groundbreaking missions, New Horizons continues to thrive as it roams over 61 astronomical units away from Earth, equipped with scientific instruments that are still actively gathering data.
At such vast distances from our planet, New Horizons has the unique ability to capture images of the cosmic ultraviolet background (CUVB) radiation, far from the inner Solar System’s glow of sunlight, gas, and dust. By studying background radiation like the CMB (cosmic microwave background), scientists can gain valuable insights into various astrophysical processes and cosmological theories.
Using its Alice instrument, the spacecraft’s Ultraviolet Imaging Spectrometer, New Horizons took 200-hour-long exposures of the Milky Way’s galactic poles in 2023. The data collected revealed a significant discrepancy in the expected levels of ultraviolet light in the targeted dark patch of sky. This unexpected brightness in the ultraviolet spectrum suggests the presence of unknown sources emitting high-energy ultraviolet light, challenging our current understanding of the universe beyond our galaxy.
While approximately half of the observed emission can be attributed to known sources like unresolved galaxies and stars, the origin of the remaining brightness remains a mystery to scientists. This intriguing discovery underscores the need for further exploration and research to uncover the elusive source behind this phenomenon. NASA’s upcoming UVEX (UltraViolet EXplorer) mission, scheduled for launch in 2030, holds the promise of shedding more light on this unexpected cosmic mystery.
In a study published on the pre-print server arXiv, the New Horizons team details their findings and the implications of this discovery. As scientists continue to unravel the mysteries of the universe, each unexpected finding brings us closer to understanding the complex and awe-inspiring nature of the cosmos.