Earth’s atmosphere is opaque to X-rays, which is probably good news for life on this planet. It is not good news for astronomers, however, because that means the best way for them to see high-energy events like black holes and neutron stars is to send a telescope into space. A bit easier than that is to send them up in the stratosphere. This is what researchers have done with XL-Calibur, a telescope that floated from Sweden to Canada on the polar winds. The rest of this article is behind a paywall. Please sign in or subscribe to access the full content.

The trip took place in July 2024 and took 6 days. Over that time, the flying observatory looked at two main sources: the Crab Nebula, the result of the supernova of 1054, and Cygnus X-1 (Cyg X-1), the first black hole ever discovered. This

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