Astronomers finally solve the gamma-Cas X-ray mystery after 50 years

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May 2, 2026, 3:43 AM

• •Gamma-Cas, a bright star in Cassiopeia, has emitted unusual X-rays.
• •The X-rays originate from a white dwarf companion accreting material from gamma-Cas.
• •XRISM data confirmed the white dwarf's role, solving a long-standing mystery.
• •The discovery provides insights into binary star systems and their evolution.

Astronomers have identified the source of unusual X-rays from the bright star gamma-Cas: an unseen white dwarf companion star. The white dwarf pulls in material from its larger neighbor, generating the X-rays. This discovery, confirmed by XRISM data, resolves a mystery that puzzled scientists for over fifty years. The findings offer new insights into binary star evolution, prompting further investigation into how these systems form and change over time.

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