At the centre of some black holes is 'an area where space and time exists'(dailymail.co.uk)
Colonies of aliens living on planets within black holes may not be as far-fetched as it sounds.
Some black holes have a complex internal structure that allows photons, particles and planets to orbit a central singularity, according to one scientist.
A singularity is the region in a black hole when space and time become infinite.
Home to aliens? Planets that orbit inside a charged and rotating black hole could exist, a scientist said. The outer ring in this image depicts a planet in orbit, while the inner rainbow ring shows orbiting photons
However, Professor Vyacheslav Dokuchaev claims that at the centre of certain black holes, and under the right conditions, is an area where the fabric of space and time exists once more.
If a charged and rotating black hole is large enough, he said, it can weaken the tidal forces that are beyond the event horizon - the point where nothing, not even light, can escape a black hole's gravity.
Scientists have long known that photons can survive in stable periodic orbits inside such charged black holes.
However Professor Dokuchaev said that a black hole's inner Cauchy horizon - the area where dimensions switch back again - can also accommodate particles and even planets.
These manage to exist without ever getting sucked all the way into the black hole and would derive light and heat from the orbiting protons and from the energy of the central singularity, he said.
An artist's impression of the tremendous gravitational pull of a giant black hole on a passing star(R) which is first stretched by tidal forces until it is torn apartProfessor Dokuchaev, from the Institute for Nuclear Research of the Russian Academy of Sciences in Moscow, speculates that these conditions could prove self-sufficient for alien life.
He said: 'This internal black hole domain, hidden by two horizons from the whole external universe, is indeed a suitable place.
'Advanced civilisations may live safely inside the supermassive black holes in the galactic nuclei without being visible from the outside.'
Earlier this year scientists discovered that the black hole M87 is almost twice as big as had previously been thought.
It was observed in M87, by far the largest and most distant galaxy some 50million light years away.
Researchers said that it may have formed as a result of hundreds of smaller black holes merging into one at some point in the past.
As a point of comparison, the black hole at the centre of the Milky Way is 1,000 times smaller.