Not all stars shine: the Universe harbors objects so compact and so massive that their light cannot escape. Black holes are among these extreme stars. Their gravitational field is so intense that no form of matter or radiation can cross their horizon, the boundary beyond which everything disappears.
Stellar black holes are born from the gravitational collapse of very massive stars. When the core of a dying star exceeds the limit allowing the formation of a neutron star, it contracts inexorably until it becomes a black hole. This process, described by general relativity, gives rise to one of the most mysterious and fascinating objects in the cosmos.
Black holes can have very varied masses: some weigh only a few times the mass of the Sun, while others, nestled at the centers of galaxies, reach millions or billions of solar masses. These galactic giants influence the dynamics of surrounding stars and play a major role in the evolution of galaxies.
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Sagittarius A*: Observations and Mysteries of the Galactic Black Hole 
Gravitational Waves: Vibrations in the Cosmic Fabric 
Primordial Black Holes: The Invisible Vestiges of the Young Universe 
The curvature of time, a non-intuitive concept!
Sagittarius A: Cosmic Monster Lurking at the Center of Our Galaxy
On the trail of invisible black holes: gravitational impact and effects on nearby stars
The Monster of NGC 1277: A Black Hole That Defies Theories
Central area of the Milky Way
The first image of a black hole