A black hole is an astronomical object with gravity so strong that nothing—not even light—can escape once it passes its event horizon, the boundary around the singularity.
Stellar black holes form when massive stars (∼20× the Sun’s mass) exhaust their nuclear fuel, undergo supernova explosions, and collapse under gravity into a point with extreme density and curvature of spacetime. If the remnant core exceeds roughly three solar masses, no known force can resist the collapse.
Supermassive black holes—millions to billions of solar masses—reside at the centers of most galaxies, including the Milky Way. Evidence comes from tracking orbital motion of stars in their vicinity, as observed by NASA and ESA facilities, evidence that earned the 2020 Nobel Prize.
Black holes are invisible, but their presence is inferred from accretion disks—hot gas swirling around them emits powerful X-rays—and from gravitational lensing, where their mass bends light from background objects.
Observations by the Event Horizon Telescope (EHT) produced direct images of the shadow of black holes in M87 and Sagittarius A*, confirming Einstein’s predictions about light structure near the event horizon.
Some black holes move at high speeds through space, likely receiving small velocity boosts (often called kicks) from asymmetric supernova explosions or galactic interactions, as detected using Hubble’s precision astrometry.
Black holes also play key roles in cosmic evolution. Tidal disruption events—where a passing star is torn apart—produce luminous flares captured by Hubble and Chandra, providing rare glimpses into black hole activity.
Their immense gravity powers active galactic nuclei and relativistic jets, influencing both their surrounding galaxies and intergalactic environments.
1 October 2024
How far can black hole jets extend? A new record was found just recently with the discovery of a 23-million light-year long jet pair from a black hole active billions of years ago. Dubbed Porphyrion for a mythological Greek giant, the impressive jets were created by a type of black hole that does not usually create long jets -- one that is busy creating radiation from infalling gas. The featured animated video depicts what it might look like to circle around this powerful black hole system. Porphyrion is shown as a fast stream of energetic particles, and the bright areas are where these particles are impacting surrounding gas. The discovery was made using data from the Keck and Mayall (DESI) optical observatories as well as LOFAR and the Giant Metrewave Radio Telescope. The existence of these jets demonstrates that black holes can affect not only their home galaxies but far out into the surrounding universe. Your Sky Surprise: What picture did APOD feature on your birthday? (post 1995)