Mystery of Cassiopeia star solved after 50 years ⚡ экспресс
The star γ Cassiopeiae, visible to the naked eye, is a prime example of Be stars (rapidly rotating giants with disks) and has intrigued astronomers for half a century with its unusually powerful hard X-rays. Observations with the XRISM satellite (Resolve instrument) captured Doppler shifts in spectral lines: hot plasma and fluorescence from cooler gas moved in sync with the orbit of a white dwarf companion. This directly linked the emission to accretion (infalling matter) onto the white dwarf for the first time. The slight broadening of the lines indicated that the glow originates on its surface, not in the accretion disk. The discovery confirms that these enigmatic sources are Be+white dwarf systems, which make up ~10% of massive stars, and provides a key to their evolutionary models.
For fifty years, astronomers couldn't understand the powerful X-rays from the star Gamma Cassiopeiae. They suspected an invisible companion, but had no proof. Japan's XRISM telescope, armed with high-resolution spectroscopy, caught tiny shifts in the emission lines. Those oscillations precisely matched the motion not of the main star, but of its tiny partner.
It turned out to be a white dwarf – a superdense stellar leftover whose maximum mass was worked out by Chandrasekhar. Gas from the big star streams toward the dwarf and, like water down a drain, spirals into a searing hot disk. There it heats to millions of degrees, giving off that very X-ray glow. The find is like solving a magic trick: we finally see where the matter disappears.
Such pairings, it turns out, aren't rare: one in ten massive stars with a disk conceals a white dwarf. This helps us grasp how supernovae and neutron stars are born. The cosmos is teeming with invisible drains, gobbling up their neighbors.
🎯 A white dwarf is so dense that a sugar-cube-sized chunk of it would outweigh a truck.