"This has been going on for some time and the date of closest approach keeps getting pushed back. Here is the latest report from the New York Times on the approach of a gas cloud called G2 towards the Galactic Center.
Black holes, which are the ultra-dense, collapsed objects predicted by Einstein's theory of general relativity, are often depicted as voracious feeders whose extraordinary gravity acts like a one-way membrane: Everything is sucked in, even light, and virtually nothing leaks out.
Now, for the first time, astronomers may have a chance to watch as a giant black hole consumes a cosmic snack.
In March or April, the gas cloud G2, which has been hurtling toward the center of the Milky Way, is expected to collide with Sagittarius A*, a black hole that lies just 26,000 light-years away from Earth."
There will be flares up in brightness in various wavebands. The variation in brightness and spectrum with time will tell us about the accretion processes taking place. In other black holes, the material appears to form a disc of accreting material. It has to lose angular momentum before it gets swallowed by the black hole. The innermost part of the accretion disc is seen by X-ray emission (reflection) and can be very variable.
The cloud is also pretty small (a few solar masses), so you're not going to get a dangerous outburst!