They may be smaller than we know
Earlier this month, a team of scientists found a compact object that stumped them: it is between 2.09 and 2.71 times the mass of the Sun, making either a massive neutron star—the dense, end stage of stellar life—or a super small black hole, the lightest known.
I know, this feels a little cheap given primordial black holes are theorized to be small and have a place on this list. But primordial black holes belong to the realm of theory—this object was observed with a radio telescope. It’s a reminder that the ranges of black hole masses are a moving target, and each observation lends itself to better understanding how the objects are born and grow.
