Stars more than 20 times the mass of the sun may have their cores collapse into black holes when they reach the end of their lives.

Astronomers have calculated, based on big data, that stars capable of producing black holes are expected to account for about one in a thousand of the proportion of stars, meaning that in the Milky Way alone, there are at least 100 million potential stellar black holes.

The cosmic black holes that scientists have discovered so far have basically been special binary star systems, where black holes are more easily detected, and where the mutual motion of a black hole and another celestial body can produce special gravitational waves. But NASA, with the help of the Hubble telescope, has discovered an isolated black hole 5,150 light-years away from Earth.

Isolated 'wandering black hole' spotted through gravitational lensing:

Black holes devour approaching light, which makes them very dark, making them difficult to spot directly in space.

Black holes exist in binary star systems, and scientists can determine the location of a black hole by the orbit of the companion star's motion, and the light it produces, but isolated black holes can't be clued in by the companion star.

The Hubble telescope has found isolated "wandering black holes" and has gotten its clues mainly through gravitational lensing produced by the black hole's gravity.

Black holes have a very high mass and a powerful gravitational field, and the gravitational field produced by a black hole can distort the surrounding space, giving it a magnifying glass-like effect, which is called gravitational lensing.

The Hubble telescope, as well as ground-based astronomical observatories, can detect 2,000 gravitational lenses a year, only a few of which are caused by black holes.

The larger the mass of the object that produces gravitational lensing, the longer it takes for gravitational lensing to produce brightening, and the more pronounced the brightening will be. Gravitational lensing produced by black holes, which generally lasts for a longer period of time, is an important distinction between black holes and other celestial objects.

Scientists first discovered isolated "wandering black holes" from a gravitational lensing event that lasted 270 days.

Because of the very long duration of the gravitational lensing, scientists thought that there might be a massive black hole in the region, and through two years of observations, scientists did not find a companion star for the black hole, so it is likely that this black hole is an isolated black hole.

The Hubble telescope conducted six years of observations and finally determined that an isolated black hole exists in the region.

Isolated black holes are difficult to observe and full of mystery:

Isolated black holes are very difficult to observe because of the limited capacity of human astronomical observation, and this part of the black hole is a very critical part for the universe.

Hawking once said that the dark matter unknown to mankind is likely to be scattered in the universe, isolated primordial black holes, due to the small size of this part of the black hole, and exists alone, so it will produce seemingly mysterious gravitational effect and mass, and thus be mistaken by astronomers as dark matter.

Primordial black holes are basically isolated "wandering black holes", but they do not go through a stellar phase, but are formed directly through pressure at the beginning of the universe, when matter and energy are relatively dense, and are therefore small, even the size of a grapefruit.

While primordial black holes can theoretically form, scientists have not observed any primordial black holes so far.

By searching for isolated black holes in the universe, scientists may be able to find definitive evidence of the existence of primordial black holes, which could help astronomers gain a more comprehensive understanding of the universe.

Astronomers have detected a massive object at the edge of our solar system, and although astronomers believe the massive object may be Planet Nine, the object has not been observed, so some astronomers believe that inside our solar system, there may be primordial black holes.

But in order to find primordial black holes, astronomers would have to acquire more powerful black hole observation capabilities and find isolated black holes in the universe.

Summary:

Human observation of the universe is very limited, especially for black holes.

The limitation of astronomical observation ability makes the detection of black holes very difficult, and therefore many unknown phenomena. With the launch of a series of space telescope projects such as the James Webb Space Telescope, perhaps in the future mankind will be able to see more secrets of the universe, so that mankind has a new understanding of the universe.