In many matters related to physics, especially in astronomy, we often hear discoveries and news about “black holes.” But, after all, what is a black hole?

Basically, a black hole is a celestial object that has a very large concentrated mass for the space it occupies. In this way, nothing can escape its gravitational field, not even the light. That is, its gravitational field is so intense that not even the speed of light is greater than its escape velocity.

And what is escape velocity?

The escape velocity is one in which the intensity is sufficient for an object to “escape” from the action of the gravitational field. On the surface of the earth, for example, the escape velocity is approximately 11.2 km/s. This means that in order for an object to detach itself from the gravity action of our planet, it must be launched with a velocity greater than 11.2 km/s.

In the case of black holes, even the speed of light (exactly 299,792,458 m/s) is not fast enough to “escape” from its gravitational field. Thus, light entering a black hole can no longer exit, so that it can not be observed by the techniques used to analyze the light emitted or reflected by the celestial objects..

If black holes can not be observed, how are they found?

Black holes are observed indirectly. What happens is that it is possible to perceive some effects that it causes in its near regions. For example, due to its immense gravitational field, the black hole ends up exerting a gravitational force on the bodies around it, producing movement in bodies that are close to it. When you notice this movement you can also detect a black hole..

In addition, when this process occurs and a black hole absorbs matter from nearby bodies, this matter is compressed, which causes it to significantly heat up and emit large amounts of X-ray radiation. This radiation is noticeable, and even that was how the first detections of black holes were made: through sensors that captured this X-ray emission..

It is also possible to discover the mass of a black hole by measuring the speed with which objects move towards them in the neighboring regions.

Did you like to know more about black holes? Keep an eye on our blog and find out several other curiosities from the world of physics.