Can light be bent by gravity

Black holes

The gravitation of a black hole is so strong that even light can no longer escape - this means that these objects can never be observed directly. However, their existence is proven beyond doubt by indirect methods.

Due to their strong gravity, black holes bend space around them. Therefore, light rays in their environment no longer run in a straight line, but are bent. Albert Einstein's general theory of relativity had predicted such curvatures of space and astronomers have now been able to confirm this many times by observing the sky. The greater the attraction of an object, the greater the deflection effect - until the rays of light at a black hole are forced onto a circular path and can no longer leave it.

Centaurus A

The entire mass of a black hole is concentrated in a single point with an infinitely high density and an infinitely strong gravitational field, a so-called singularity. Nevertheless, a size can be assigned to these objects, for which astronomers use the event horizon. Beyond this limit, neither light nor matter can escape the black hole. Black holes differ from each other particularly in terms of their mass and the history of their formation. They can be divided into the following groups:

  • Super massive black holes have a mass of about 105 until 1010 Solar masses. So far it is unclear how they came about and how they developed. Researchers assume that there is a supermassive black hole in almost every galaxy center. The black hole, which is located in the center of the Milky Way, also belongs to this category with 3.6 million solar masses. If the black hole is surrounded by a rotating disk of gas and dust, the material can heat up and begin to glow extremely brightly. Such phenomena are called Seyfert galaxies or quasars.

  • Stellar black holes have a mass of a few to a few tens of solar masses. Stars with more than ten solar masses end in huge cosmic explosions, so-called supernovae. They repel their shell as a gas cloud into interstellar space, their core collapses under the strong gravity within a few seconds to minutes to form a black hole.

  • Researchers suspect another group medium-weight black holesthat are said to have a mass of several hundred to several thousand solar masses. So far, however, no objects of this class have been clearly identified. Astronomers found the first indications of medium-weight black holes in young star clusters, globular star clusters and dwarf galaxies. Researchers assume that these objects are created by collisions between several stars.