Found it for the first time!

Believe in science.

The great mass of a black hole produces such a strong gravitational field that light cannot escape.

Therefore, we can not detect black holes directly by detecting visible light, X-rays or any other form of electromagnetic waves. We can only infer the existence of black holes by their effects on other nearby matter.

For example, the interaction between a black hole and a companion star in a binary system can produce light or gravitational waves, from which we can know the existence of a black hole.

However, if there is no other matter around some black holes, how can we find them?

Now is the boom in the search for black holes.

We have found supermassive black holes (supermassive black holes) with masses equivalent to billions of solar masses at the center of almost every galaxy, and have imaged one of them.

Now, researchers often detect gravitational waves from the merging of smaller black holes.

Closer to Earth, we witness the spectacular cosmic "fireworks" of supermassive black holes in the Milky way and their smaller counterparts as they devour gas clouds and stars.

However, there is a long-predicted effect that we have never observed: black holes born from the collapsing cores of massive stars, thrown out and wandering aimlessly in the universe.

Now, we have finally found their whereabouts.

Gravitational lens.

In 1919, British astronomer Arthur Stanley Arthur Stanley Eddington did a famous experiment.

Einstein's theory of special relativity and general relativity hypothesized that massive objects would cause depressions in space-time, causing light nearby to bend, a process known as gravitational lenses.

Eddington proved the existence of this phenomenon during a total solar eclipse.

When a total solar eclipse occurs, the glare of the sun is minimized so that we can see stars adjacent to the sun in the space background.

Using astrometric techniques, Eddington carefully recorded the coordinates of these stars when they were not in the same sky region as the sun and when they were in the same sky region as the sun (during the eclipse), and found that their positions changed slightly. This is because the light they emit is distorted by the sun's huge gravity, which in our view has changed its position.

In the decades that followed, scientists discovered new uses for astrometry.

Stars more than 20 times the mass of the sun form black holes at the end of their lives because their heavy cores collapse due to their own weight when thermonuclear fuel is exhausted.

The resulting stellar mass black hole (stellar-mass black hole) is about a city-sized sphere with dozens of times the mass of the sun.

Their birth is usually accompanied by bright supernovae caused by the huge energy released by the collapse of the core.

Supernova explosions are so powerful that they sometimes kick newborn black holes out of the womb that gave birth to them, making them vagrants in the universe.

Coupled with the small size and dark nature of these black holes, they are almost impossible to see.

However, Eddington's experiments inspire us that these "vagrants" can be found through the gravitational lens effect.

When a black hole passes over a star in the background in our field of view, the star brightens instantly.

For a black hole, it is highly unlikely that such an event will be observed, but since millions of stellar-mass black holes are expected to be drifting in our galaxy, as long as the sky is investigated extensively and deeply enough, some black holes may be found.

A star that suddenly brightens.

Some projects are looking for such microgravitational lens events, such as the Optical gravitational Lens experiment (OGLE) at the University of Warsaw, Poland, and Astrophysical Microlens observations (MOA) conducted in New Zealand and Japan.

In June 2011, the two projects discovered a remarkable phenomenon: in the direction of the center of the Milky way, a star suddenly brightened.

Could this be a microgravitational lens event caused by a wandering black hole? astronomers are scrambling for answers.

Using the Hubble Space Telescope, the lead author of the new study, Kailash Sahu, and colleagues magnified the star within weeks of brightening, and repeatedly observed it over the next six years.

They confirmed that the star's light was indeed magnified, indicating the existence of an invisible object that acts as a gravitational lens.

They also made a more important discovery-a slight change in the apparent position of the star in space.

"this change is 1000 times smaller than Eddington's measurements and is close to the limit of the Hubble Telescope," Sahu said. "

Something invisible magnifies and distorts the light emitted by the star.

What is the most reasonable possibility-a stellar black hole with a mass about 7.1 times that of the sun.

Sahu said that apart from black holes, there is no other possibility.

Two criteria are needed to confirm this: one is that there should be no light on the "lens", which excludes more common objects, such as brown dwarfs, and that the magnification effect should last for a long time, given the wide range of gravitational influence of the black hole. The June 2011 effect lasted about 300 days, which is also in line with the requirements.

"their analysis is very detailed."

Badri evaluation.

By calculating the degree of light deflection, Sahu and his colleagues determined that the mass of the black hole is a little more than seven times the mass of the sun.

"this is right in the middle of our expectations for the mass of stellar mass black holes."

Said Feryal zel of the University of Arizona, who was not involved in the study.

The team also calculated that it was moving at a speed of 45 kilometers per second.

Compared with nearby stars, this movement is relatively fast, and it is expected that a black hole kicked out by a dying massive star should get a higher speed.

"it is not clear when the black hole began to wander, probably nearly 100 million years ago," Sahu said.

Because we don't know where it came from, we can't be sure. "

In fact, this is not the first clue that stray black holes cause microgravitational lenses.

Before that, scientists have several other candidates.

But the difference in this incident is, Coe.