US EditionAstronomers Solve 50-Year Mystery of a Naked-Eye Star’s Extreme X-Rays
XRISM observations confirm Gamma Cassiopeiae's intense X-rays come from a magnetic white dwarf accreting material, representing about 10% of massive Be stars, researchers say.
- On Tuesday, March 24, 2026, researchers published findings in Astronomy & Astrophysics confirming that Gamma Cassiopeiae's intense X-ray emissions originate from a hidden white dwarf companion detected by Japan's XRISM space telescope.
- For 50 years, astronomers have been baffled by Gamma Cassiopeiae, a massive Be-type star emitting X-rays 40 times more powerful than expected, with plasma temperatures exceeding 100 million degrees.
- Observations using the high-precision Resolve instrument aboard XRISM tracked the system over 203 days, revealing plasma velocity shifts matching the white dwarf's orbital motion rather than the Be-type star.
- This discovery confirms the existence of a new class of binary systems, identifying Gamma Cassiopeiae and similar objects as Be-type stars paired with magnetic white dwarfs, resolving a long-standing debate.
- Astrophysicist Yaël Nazé of the University of Liège stated that understanding these interactions enables researchers to create specific models for this stellar class, updating binary evolution theory accordingly.
14 Articles
14 Articles
Astronomers solve 50-year mystery of a naked-eye star’s extreme X-rays
A star you can see with the naked eye has kept astronomers guessing for decades with its unusually powerful X-rays. Now, thanks to highly precise observations from Japan’s XRISM space telescope, scientists have finally uncovered the source: a hidden white dwarf companion pulling in material and generating extreme heat. This discovery not only solves a 50-year-old mystery surrounding Gamma Cassiopeiae, but also confirms the existence of a long-pr…
A research led by astronomers from the University of Liège in Belgium has identified the origin of the mysterious X-ray emissions of the star γ Cassiopeia (better known by its nickname “γ Cas”), located in the constellation of Cassiopea . Based on observations made by the Japanese XRISM space telescope, scientists demonstrated that extreme radiation is produced by a white magnetic dwarf orbiting the star, and not by the γ Cas itself, as some hyp…
A research led by the University of Liège in Belgium identified the origin of the unusual X-ray emissions of the star Gamma Cassiopeiae. The finding solved a scientific enigma that persisted since 1976.The data from the Japanese XRISM space telescope allowed to determine that the radiation comes from a white magnetic dwarf orbiting the star.The study was published in March in Astronomy & Astrophysics magazine.The evidence also confirmed the exis…
A Bright Star Hid a Massive Secret for 50 Years: Mystery of Gamma Cassiopeiae Finally Solved
A naked-eye star’s 50-year mystery is solved—its bizarre X-rays come from a hidden, feeding white dwarf. Easily visible in the night sky within the constellation Cassiopeia, the star γ Cas has puzzled astronomers for more than 50 years. It produces X-rays with energies and temperatures far beyond what is expected from a typical massive star. [...]
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