A Mirror Built With Nanometer Accuracy<\/p>\n
The heart of the telescope lies in its mirror, a component that must meet unusually strict requirements. X-rays<\/a> do not behave like visible light and can only be reflected at very shallow angles. This requires surfaces shaped with nanometer-level precision.<\/p>\n To meet this challenge, the team used a precision electroforming method developed at SPring-8. As reported by the study published in Publications of the Astronomical Society of the Pacific<\/a>, they produced a nickel mirror measuring60 mm in diameter and 200 mm in height.<\/p>\n This mirror differs from conventional designs in one key aspect. It is a single seamless shell. Without joints or seams, there are fewer opportunities for misalignment or deformation. As Ikuyuki Mitsuishi<\/a>, the project leader at Nagoya University\u2019s Graduate School of Science explained:<\/p>\n \u201d The mirror is like a very precise funnel for X-rays. If any part of the funnel is even slightly out of place, the X-rays miss their target and the image blurs.\u201d He added, \u201cIt must also survive the intense vibrations of a sounding rocket launch while retaining its optical precision.\u201d <\/p>\n Recreating Starlight in the Lab<\/p>\n Before sending the telescope <\/a>into space, researchers needed to verify its performance under realistic conditions. This posed a fundamental difficulty, since starlight reaches Earth as nearly parallel rays due to the vast distances involved.<\/p>\n To replicate this, the team designed a dedicated testing system at SPring-8. According to the researchers, they placed a 10-micrometer X-ray source roughly 900 meters away from the mirror. At that distance, the rays remain sufficiently parallel to simulate those coming from distant stars.<\/p>\n This approach enabled precise measurement of the telescope\u2019s angular resolution. Ryuto Fujii<\/a>, first author of the study, stated that:<\/p>\n \u201cIt\u2019s the first ground-based system capable of accurately evaluating the performance of\u00a0high-resolution X-ray space telescopes<\/a>\u00a0at hard X-ray energies, and it is available to researchers worldwide who want to develop and test similar technology.\u201d<\/p>\n A Successful Test In Space With FOXSI-4<\/p>\n The telescope was later flown aboard FOXSI-4<\/a>, a sounding rocket mission launched from Alaska on April 17, 2024. The mission carried seven X-ray telescopes designed to observe the Sun\u2019s activity. <\/p>\n Based on the mission data, the instrument successfully observed an active solar flare<\/a>, confirming its capabilities in real conditions. This flight marked the first participation of a domestically developed Japanese high-resolution X-ray telescope in an international sounding rocket program.<\/p>\n Researchers identified that the main limitation in image sharpness comes from tiny imperfections along the mirror surface. These findings provide a clear direction for improvement. An updated version of the telescope is planned for FOXSI-5<\/a>, scheduled for 2026.<\/p>\n![\"Compact](\"https:\/\/www.newsbeep.com\/ca\/wp-content\/uploads\/2026\/04\/Compact-X-ray-mirror-design-shown-inside-the-telescope-and-ready-for-launch-1200x723.jpg.webp.webp\")
Compact X-ray mirror design shown inside the telescope and ready for launch. Credit: Fujii & al.<\/p>\n![\"X](\"https:\/\/www.newsbeep.com\/ca\/wp-content\/uploads\/2026\/04\/X-rays-travel-900-meters-before-reflection-and-detection-in-a-vacuum-setup-1200x919.jpg.webp.webp\")
X-rays travel 900 meters before reflection and detection in a vacuum setup. Credit: Fujii & al.<\/p>\n