Rho Cassiopeiae

A rare yellow hypergiant star, Rho Cassiopeitae habitually releases quantities of ejecta equal to 10,000 planets, lifted into space by a blast wave.

The phenomenon is similar to the shock wave a jet produces, which can be heard as a sonic boom. Gas rushes outward at four times the speed of sound.

The star has been restless, its atmosphere pulsating wildly, with no cadence. Its outer atmosphere seems to be collapsing again, an event that signals another eruption -- possibly a stronger one -- could be imminent.

Because of the star's advanced age, it could go supernova in as little as 50,000 years.