In the universe, black holes are one of the most curious, extraordinary and unusual entities. Many people do not know that our galaxy has a black hole at its center.
In this article we're going to tell you some interesting facts about the black hole at the center of our galaxy.
Curiosities about black holes
It is impossible to observe a black hole directly.
The name black hole comes from the fact that light cannot escape its reach, as the speed required to do so exceeds the speed of light, which is considered impossible according to the laws of physics; therefore, it does not emit light. However, we can observe the consequences of a black hole. By examining the area surrounding a black hole, we can witness its impact on the environment.
For example, you can observe how a star is torn apart when it gets too close to a black hole. This phenomenon led to the first observations of a black hole, including images captured of the one in the galaxy M87. If you want to better understand how these mysterious objects are detected, you can visit the page on the process of detecting black holes using images.
At the center of the Milky Way, there is a black hole
There's no cause for concern. We're safe, as this supermassive black hole, known as Sagittarius A*, is located 25.000 light-years away. For more details about its size and characteristics, check out the black hole in the Milky Way.
Stellar black holes form from dying stars
The formation of stellar black holes occurs after the demise of extremely massive stars, as the star's gravity overcomes the inherent pressure that holds its structure together. When the pressure from nuclear reactions decreases, gravity causes the star's core to collapse, resulting in the outer layers being ejected into space in a phenomenon known as a supernova. The remaining core continues to collapse under immense density, ultimately creating a black hole in the absence of volume. If you'd like to understand how a black hole forms, visit How a Black Hole Forms.
The nature of black holes is relative
Imagine a scenario where a person tragically falls into a black hole while an observer is present to witness this event. The observer would notice that the time experienced by the person falling into the black hole appears to slow down compared to their own time, effectively coming to a standstill near the black hole. This phenomenon is explained by Einstein's theory of general relativity, which states that time is influenced by the speed at which we travel , particularly at immense speeds approaching the speed of light. To delve deeper into this topic, see What does a black hole sound like?
It was not until the advent of X-ray astronomy that the first black hole was discovered.
Discovered in the 1960s, Cygnus X-1 was the first black hole identified and has a mass ten times that of the Sun. To learn the story of its discovery, you can visit .
Black holes only become dangerous when you get too close.
While it's generally safe to study black holes from a distance, getting too close poses significant risks. This also suggests that a black hole is unlikely to engulf an entire universe, as the gravitational influence diminishes greatly with increasing distance.
A black hole is very close to Earth
A massive black hole, approximately 12 times the mass of the Sun, has been discovered just 1.550 light-years from the solar system . This black hole is accompanied by a star very similar to our Sun. For more details about these nearby objects, see nearby black holes.
Interesting facts about our galaxy's black hole
The supermassive black hole at the center of our galaxy, known as Sagittarius A* (Sgr A*), is one of the most fascinating objects in the universe. Located at the heart of the Milky Way, about 26,000 light-years from Earth, this supermassive black hole has a mass equivalent to approximately 4 million times that of our Sun. Although the black hole itself does not emit light, we can infer its presence from the behavior of nearby stars, which orbit at incredibly high speeds due to its immense gravity. This image shows details of how it appears from Earth.
One of the most interesting facts is that despite being so massive, Sagittarius A is relatively small in size. The event horizon, which is the boundary beyond which not even light can escape, is only about 24 million kilometers in diameter, which is huge in human terms, but tiny compared to its colossal mass.
Another curious fact is that this black hole appears to be "quiet" compared to other supermassive black holes. Although it may have been much more active in the past, it is not currently absorbing large amounts of material. This is a relief, because if Sagittarius A* were in a more active phase, the amount of energy released could affect the conditions for life in our galaxy.
Also in 2022, the Event Horizon Telescope (EHT) captured the first image of Sagittarius A's shadow. Although the image is a bit blurry, it's an important milestone, as it confirmed many theories about black holes, including their existence at the center of our galaxy. For a more technical explanation, see .
Other curiosities of Sagittarius A
The stars near Sagittarius A*, known as "S stars," are key to measuring the black hole's mass. These stars have extremely fast and eccentric orbits. For example, the star S2, which is about 17 light-years from Sagittarius A*, completes an orbit in just 16 years and reaches speeds of up to 7,650 km/s (2.5% of the speed of light) at its closest point. You can learn more about these movements in What Happens When a Black Hole Goes from Dormant to Active.
While supermassive black holes like Sagittarius A "feed" on gas, dust, and stars that stray too close, ours appears to be on a "diet" basis. It's thought to absorb only a small amount of matter, which could explain why it doesn't emit large bursts of energy like other active black holes.
Despite the enormous mass of Sagittarius A*, it has no significant impact on the solar system . We are far enough away that its gravitational influence does not noticeably affect the orbits of the planets or the conditions for life on Earth. In fact, the gravity of the nearest black hole to the solar system (which is not supermassive) has more influence on us than Sagittarius A*.
