Search for 'Planet Nine' Yields Unexpected Discovery

Astronomers have long been on the hunt for "Planet Nine," a hypothetical planet that lies within our solar system just beyond Neptune. Scientific evidence has alternately pointed to and against the existence of such a planet, but the search is still on, stoked by the 2006 demotion of Pluto to "dwarf planet." This time, scouring the cosmos may have yielded a concrete result—it's just not the kind astronomers were hoping for.

A small team of researchers at the Institute for Advanced Study and Princeton University spent half a year sifting through data from the Victor M. Blanco Telescope's Dark Energy Camera Legacy Survey (DECaLS). Gathered in 2019 by the telescope's Dark Energy Camera, or DECam, the archive consists of wild-field optical imaging data from the green, red, and z bands. Though these filters make it possible to search for distant space objects via photometric redshift, no ...