The supermassive blackhole at the center of our Milkyway. Discovering which two physicist received the Nobel this year.
You can watch the single star at the center of this video, how it's going around the blackhole in circles at extremely high speed compared with other stars around. Its speed here is around 2.5% the speed of light. The Nobel winners proved that it can't be anything but a supermassive blackhole sitting at this point.
The blackhole's mass is : 4 million suns.
Diameter : a third of distance between sun and earth. 0.3 AU.
Note, a supermassive blackhole is still comparatively as small as any other star. Not that it takes out 10% of the galactic space to sit at its center.