If there’s a stellar object that’s both scaring and fascinating at the same time is the black hole. Scientists are still debating about what its nature truly is, and recent findings only add to its mystery. An accepted definition for it is “a mathematically defined region of spacetime exhibiting such a strong gravitational pull that no imminent particle or electromagnetic radiation can escape from it” , predicted by the theory of general relativity even before being discovered. Black holes come in different sizes, they are often located at the centre of galaxies (the Milky Way has its own, Sagittarius A*) and sometimes display odd behaviours. Here a small gallery of these fascinating objects:
A stellar, young black hole
(Credit: NASA)
…comparatively small in size and formed by the collapse of a star (such as the two distant dust-free quasars spotted recently by the Spitzer Space Telescope)
Abell 1795: Death By Black Hole In Small Galaxy?
(Credit: CHANDRA)
Cygnus X-1 binary star system (the first object to be considered a black hole)
(Credit:NASA)
As the NASA webpage dedicated to them explain in great detail, “don’t let the name fool you: a black hole is anything but empty space. Rather, it is a great amount of matter packed into a very small area – think of a star ten times more massive than the Sun squeezed into a sphere approximately the diameter of New York City. The result is a gravitational field so strong that nothing, not even light, can escape.” Indeed.
Sagittarius A*: New Evidence For A Jet From Milky Way’s Black Hole
(Credit: CHANDRA)
RX J1532.9+3021: Extreme Power of Black Hole Revealed
(Credit: CHANDRA)
Hubble Site is another good source of information about them, with also some cool images.
By the way: The term “black hole” was coined in 1967 by the astronomer John Wheeler, and the first one was discovered in 1971. The movie Interstellar have made black holes recently popular again. Here Kip Thorne, the physicist that created them for the movie, tells the story.