Maps of energetic neutral atom flux from 2009 to 2022 and from 0.71 keV to 4.29 keV. Click to enlarge. [Noh et al. 2025]
In 2009, a small octagonal spacecraft called the Interstellar Boundary Explorer (IBEX) began mapping the edge of our solar system. IBEX measures the flux of
energetic neutral atoms: fast-moving, electrically neutral atoms that form when high-energy positively charged ions from the solar wind steal an electron from neutral atoms of the interstellar medium. In addition to the expected ebb and flow of energetic neutral atoms, IBEX found something completely unexpected: a narrow, curved region where these atoms are especially prevalent, shown in the images above and to the right. This feature, known as the IBEX ribbon, is still something of a mystery, though many researchers have converged on the idea that the ribbon is generated just past the heliopause — the boundary of our solar system — up to a few hundred astronomical units beyond that boundary. To enable detailed studies of the IBEX ribbon, Sung Jun Noh (Los Alamos National Laboratory) and collaborators applied a new statistical technique to the IBEX measurements, allowing them to sharpen images of the ribbon and extract its properties in regions where the signal was previously thought too weak. This results of this new analysis support the idea that the ribbon arises beyond the boundary of our solar system. To learn more about efforts to understand the IBEX ribbon, be sure to check out the original research article linked below.
Citation
“Characteristics of the IBEX Ribbon and Their Implications for a Source Region Outside the Heliopause,” Sung Jun Noh et al 2025 ApJ 980 8. doi:10.3847/1538-4357/ada36a
