Harvard scientists will attempt to determine if hypothesized ninth planet is actually a black hole

Scientists at Harvard say a new detection method may allow them to finally settle whether or not a miniature black hole—or an undiscovered planet—lies in the outer regions of the Solar System. 

Gravitational perturbations of minor planets and small astronomical objects far past the orbit of Neptune have led many astronomers to conclude that a planet exists outside even the orbit of Pluto. The hypothetical planet has been dubbed "Planet Nine," following the eight other known planets in orbit around the Sun. 

Yet some scientists have theorized that, instead of a planet, the gravitational anomaly could be explained by the presence of a small black hole, one about the size of a grapefruit.

Harvard astronomers say they plan to use the Vera C. Rubin Observatory, currently under construction in Chile, to observe any possible "accretion flares" from the theoretical black hole consuming any astronomical objects that fall into it. These flares are the "only way to illuminate" a black hole, Harvard Frank B. Baird Jr. Professor of Science Avi Loeb said in a university press release this week. 

Any black hole discovered by the scientists would qualify as "planet-mass," rendering it much smaller than the monstrous black holes that are postulated to exist at the centers of most galaxies. 

Citing the relative proximity of the theoretical Planet Nine, Loeb said that discovering such a new astronomical object in our solar system would be "like discovering a cousin living in the shed behind your home which you never knew about."