December 4, 1997: Some stars in double-star systems have found a quick way to lose weight by dumping their extra pounds onto their companions. Astronomers using the Hubble telescope have discovered such a case in the double-star system Phi Persei. A "rapid diet" program has trimmed an aging, once massive star to a lean one solar mass, while the once mild-mannered, moderately massive companion has bulked up to a hefty nine solar masses and is spinning so violently that it's flinging gas from its surface.
Taken from the perspective of the Hubble telescope's observations of Phi Persei, this artist's depiction provides a taste of the double-star system's unstable existence. The star shedding pounds is represented as the white, semicircular object looming in the upper right of the illustration. The red, pancake-shaped object surrounding it is a gas disk. The gas is material the star is losing because of its rapid rotation. The small, hot sub-dwarf in the lower left of the illustration is the star that is benefiting from its companion's weight-loss program.See the rest: