Added 1 new A* page:The supermassive black hole at the center of our galaxy, the source of a radio signal designated Sagittarius A*, made the news today! New articles from the BBC and the ESO (thanks to a reader for that link : ) describe how the ESO's observations of the star, called S2, as it whipped around A* at nearly 3% the speed of light—it does this every 16 years; last time, observations of its incredible acceleration gave the proof of A*'s existence!—showed its light being subtly stretched, or redshifted—an effect which can only be due, once other factors such as the star's velocity are accounted for, to the intense gravitational field of the supermassive black hole.
So, this is the first observation of gravitational redshift due to the gravitation of a supermassive black hole, something Einstein's theory of General Relativity predicted—quite precisely, as it turns out. It means that light escaping from the gravitational field is reddened—more specifically, the frequency of the light is reduced (red light is lower frequency than blue light). This is due to gravitational time dilation: "if one is outside an isolated gravitational source, the rate at which time passes increases as one moves away from that source. As frequency is inverse of time (specifically, time required for completing one wave oscillation), frequency of the electromagnetic radiation is reduced in an area of higher gravitational potential"—so time is, in effect, speeding up for light escaping from a black hole; it is able to complete fewer oscillations per the faster periods of time it encounters as it gets farther away from the hole's gravitational pull, which means it has a lower frequency, which means it shifts toward the red (lower frequency) end of the spectrum. I think. : o
Anyway, good job, A*! : D = oo (I may need to start using more red watercolor. : o)
|
