Very interesting. The previously-released M87 image had just a single "shadow", but this one (of Sag A*) has multiple bright "lumps". Maybe it's in the linked papers which I haven't gotten to yet, but why the difference? Is it due to the observation method or does it reflect a real difference? Or both?
From the announcement presentation, this happened due to this image being an average of many, many different images. Due to it's size, the motion of the accreting material around SgtA* moves much, much faster relative it than the material around M87. While the accreting material around both BHs move at similar speeds, M87 is about 2000x more massive than SgtA. Due to that, the material around M87 takes weeks to orbit it, while the material around SgtA takes hours. Since each data point can be minutes or hours apart, the final image for a single data point can vary greatly between other measurements, and thus the need to average everything. To put things in perspective, we just confirmed through this image that SgtA*'s shadow is about the size of the orbit of Mercury around the Sun. M87's shadow, on the other hand, has a radius larger than the distance of the Voyager probe to the Sun.
Yeah I was wondering the same. From the M87's images I understood that the bright part of the ring was moving towards us, that's why it was brighter.
But with this explanation, how can there be 3 bright lumps then on Sag A's ring ..
