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Vega is said to rotate at about 87 percent of the speed that would tear it apart. If it ever reached that speed, what would an observer on Earth witness?

Ralph Heide, El Segundo, California
RELATED TOPICS: STARS | VEGA
Hot, rapidly spinning stars can sometimes break up as they expan, creating hot, gaseous disks.
A hot star, such as Vega, will gradually increase its luminosity and also grow in size as it ages. As the star expands, it should actually spin slower to conserve angular momentum — just like an ice skater stretching out her arms. At the same time, the core is becoming more dense and compact as hydrogen is “burned” to helium ash, and thus the inner layers of the star should spin faster. Interestingly, observations show that the core and outer layers of the stars mostly synchronize their spin through viscosity so the speed of the star’s surface remains roughly constant during this time.

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