Image black hole

Black holes

The figure shows a binary system made up of a star and a black hole. The star is on the top-left; moving diagonally towards the bottom-right, the figure shows the external gas that is dragged away and sucked in by the black hole. The gas is attracted to the black hole and rotates around it. Then it spirals very slowly down into the hole, almost like a vortex.

These extremely compact celestial bodies were once big stars, six or seven times bigger than the Sun, which collapsed under the action of their own gravity into an incredibly small area, even smaller than the area occupied by the Earth.

Their force of attraction is so strong that it traps, not only mass particles but also electromagnetic radiation, such as light. As a consequence these holes are not visible given that they don’t emit any signal at all, let alone light waves. However, their presence can be detected by observing the effects that these objects have on nearby matter.

A black hole cannot be seen directly but, as the figure shows, the effects caused by its strong pull on its fellow star makes it easier for us to discover them: these effects are represented in the figure by the gas which is dragged away from the star and by the ensuing vortex that the gas creates around the invisible black hole.

According to theorists, the nearest black hole to us is only 15 light years away, it would take us about 4400 million years to walk such a distance.

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