Dana Berry/NASAFor a long time, black holes were known to exist only in the imaginations of theorists. NASA/CXCWhen black holes orbit another object, they can siphon and accelerate matter, creating X-ray and radio signatures. ESA, retrieved via http://chandra.harvard.edu/resources/illustrations/blackholes2.htmlBlack holes also gravitate; we can infer a black hole's presence as it influences its companions. Teresita Ramirez/Geoffrey Lovelace/SXS Collaboration/LIGO-Virgo CollaborationSagittarius A*, at the center of the Milky Way, is the closest supermassive black hole, some 25,000 light-years distant. Digitized Sky Survey 2, N. Risinger (skysurvey.org)As our methods and surveys continue to improve, closer black holes will inevitably be discovered.

Source: Forbes May 11, 2020 06:00 UTC