Black Hole
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.
Sources
APODs including "Black Hole"
Huge Void Implicated in Distant Universe
27 August 2007
What has created this huge empty volume in the universe? No one is yet sure, and even the extent of the estimated billion-light year void is being researched. The void is not a hole in space like a black hole, but rather a vast region of the universe that appears to be mostly devoid of normal matter and even dark matter. The void is still thought to contain dark energy, though, and is clearly traversable by light. The void's existence is being postulated following scientific curiosity about how unusually cold spots came to appear on WMAP's map of cosmic microwave background (CMB) radiation. One possibility was that this CMB region was not actually very cold but light from the spot somehow became more cosmologically redshifted than normal along the way. Other voids in the universe are known to exist, but this void appears to have an unusually large gravitational effect, and so might possibly be the largest in our entire visible universe. Investigating this, a recent study found an unusually low number of cosmic radio sources between Earth and the CMB cold spot, which led to the inference of this giant void. An artist's depiction of the huge cosmic void is shown above.