Added 1 new A* page:Reader honza1 linked me to a LiveScience article talking about a recent study—based on the orbits of stars around the supermassive black hole at the center of our galaxy, designated Sgr A*—appearing to find that our galaxy's central supermassive black hole is spinning relatively slowly: no faster than a mere 10% of the speed of light.
This Forbes article, for instance, describes the supermassive black hole at the center of galaxy NGC 1365, spinning at 84% of the speed of light—and that is in fact its maximum speed, because energy radiates away as gravitational waves, constraining further energy buildup.
The Forbes article also explains why supermassive black holes tend to spin quickly: like a spinning ice skater whose speed increases when they pull in their arms, the black hole has pulled all its mass in, lending that infinitesimally small volume vast angular momentum.
So 10% light speed—or less—for A* would be a pretty slow spin speed, but the researchers calculated that if A* was spinning any faster, its forces would have whipped away the stars currently orbiting it closely. They think they'll get a better idea of its spin speed whenever we get a sharper photo of the black hole's shadow.
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The original 16" x 6.75" watercolor art for today's new A* page is up for auction on eBay. : )
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