In 2025, the NICER X-ray telescope aboard the ISS monitored the outburst of black hole 4U 1630−47, a binary system where matter from a companion star falls onto the compact object. Analysis revealed quasi-periodic oscillations (QPOs)—rhythmic flux variations with frequencies from 0.24 to 3.43 Hz—and
arXiv:2607.02228v1 · 2026-07-02