NASA's New Horizons spacecraft, currently over 8.5 billion kilometers from Earth, has achieved a groundbreaking milestone by capturing the first-ever map of the galaxy using Lyman-alpha emissions. This achievement, detailed in a study led by the Southwest Research Institute (SwRI), provides a novel perspective on the galactic region surrounding our solar system.
Lyman-alpha, a specific ultraviolet wavelength emitted and scattered by hydrogen atoms, is crucial for understanding the composition, temperature, and movement of distant stars and galaxies. The extensive observations, which included scans covering approximately 83% of the sky, were conducted using the Alice instrument aboard New Horizons.
The findings, published on April 21, 2025, in The Astronomical Journal, indicate a roughly uniform background Lyman-alpha sky brightness ten times stronger than expected. This suggests that hot interstellar gas bubbles, like the one encompassing our solar system, may be regions of enhanced hydrogen gas emissions. The research also found no significant contribution from a hypothesized hydrogen wall at the heliosphere's edge. These new insights offer valuable tools for modeling galaxy evolution and exploring the processes that lead to the formation of new planetary systems.