Astronomers estimate that there are around 100 million black holes roaming the stars in our galaxy, but so far they have not identified a single black hole. However, after six years of meticulous observations, the Hubble Space Telescope has provided the first direct evidence of a lone black hole drifting through interstellar space by precisely measuring the mass of the phantom object. It's about a black hole in the Milky Way.
In this article, we'll tell you about the characteristics, origin, and much more about the lone black hole in the Milky Way.
what is a black hole
First of all, you have to know well what a black hole is since there are many myths about it. A black hole is an astronomical phenomenon that arises when a massive star collapses under the influence of its own gravity. giving rise to a region of space with incredibly high density and extremely strong gravitational pull. Under these conditions, matter is compressed in such a way that its volume is reduced to practically zero, creating a singularity, a point of infinite density at the center of the black hole.
The distinguishing feature of a black hole is its event horizon, which is an imaginary boundary around it beyond which neither light nor anything else can escape. This means that any object that crosses this boundary will be hopelessly trapped inside the black hole, giving the appearance of a "hole" in space.
Black holes are not directly visible, since they do not emit light, but their presence can be inferred through their effects on surrounding matter. To better understand their formation, one can look at how black holes form in other stars, as this process is crucial for identifying the origin of black holes in the Milky Way.
Black hole in the Milky Way
So far, all black hole masses have been inferred statistically or through interactions in binary star systems or galactic nuclei, making this a very special discovery.
The newly discovered rogue black hole lies about 5.000 light-years away in the Carina-Sagittarius spiral arm of the Milky Way galaxy. However, their findings allowed astronomers to estimate that the nearest isolated stellar-mass black hole to Earth might be only 80 light-years away, which is relatively close considering that the nearest star to our solar system, Proxima Centauri, is just over 4 light-years away. Stellar-mass black holes are often found with companion stars, making this one unusual and highlighting the importance of understanding more about black holes in our universe.
Black holes in the Milky Way are born from rare giant stars at least 20 times the mass of the Sun, which make up less than one-thousandth of the total number of stars in the Milky Way. These stars explode as supernovae, whose cores are crushed by gravity and become black holes. Since the self-explosion is not perfectly symmetrical, this black hole could propel itself and shoot through our galaxy, becoming a rogue black hole. For more information, you can explore fun facts about the black hole in our galaxy.
Detection of black holes
Telescopes can't photograph a wayward black hole because it emits no light. However, a black hole warps space, which then bends and amplifies the light from a star, or whatever is temporarily behind it.
So, to detect black holes, ground-based telescopes monitor the brightness of millions of stars in rich star fields and in the direction of the central bulge of the Milky Way, looking for a sudden, pronounced brightening that reveals massive black holes. Objects pass between us and the stars.
The distortion of space caused by the gravitational pull of a foreground object passing in front of a distant star temporarily bends and amplifies the light from the background star as it passes in front of it. Astronomers use this phenomenon, called gravitational microlensing, to study stars and exoplanets. But the foreground black hole's signature is unique among other microlensing events, making it critical for understanding our galaxy.
The strong gravity of the black hole will extend the duration of the lensing effect by more than 200 days. Also, if the intermediate object is a foreground star, it can cause a brief color shift in the measured starlight because the light from the foreground and background stars temporarily mix. But no color changes were observed during gravitational microlensing events.
Hubble was then used to measure the black hole's mass, distance, and speed. That led Kailash Sahu's team at the Space Telescope Science Institute in Baltimore, Maryland, to estimate its mass at about seven solar masses. The first image of a black hole, for example, has revolutionized our understanding of these phenomena, as seen in the first image of a black hole obtained by the Event Horizon Telescope team.
Alternative explanation of the black hole in the Milky Way
For its part, another team of astronomers led by Casey Lam of the University of California, Berkeley, who also studied the phenomenon, reported slightly lower measurements of its mass, which means that the object could be a black hole or a neutron star. , so yes they do. I do not rule out the second possibility.
Therefore, they estimate that the mass of the invisible compact object is between 1,6 and 4,4 times the mass of the Sun. At the high end of the range, the object will be a black hole; at the high end of the range, the object will be a black hole; at the high end of the range, the object will be a black hole. At the low end, it would be a neutron star.
Although there are an estimated 100 million isolated black holes roaming our galaxy, for Hubble astronomers, finding even the slightest hint of one is like looking for a needle in a haystack.
“As much as we want to say that it is definitely a black hole, we have to consider all the options. This includes less massive black holes and perhaps even neutron stars," explained Jessica Lu of the Berkeley team. "But whatever it is, this object is the first dark star remnant found in the Milky Way without the company of another starRam added.
Obtaining the measurements was a difficult task for both teams because another very bright star was very close to the observed object. "It's like trying to measure the tiny movements of a firefly next to a bright light bulb," Sahu said. "We had to carefully subtract light from nearby bright stars to accurately measure the deflection from the faint source."
Sahu's team estimates that the isolated black hole travels through the Milky Way at 100.000 miles per hour, fast enough to travel from Earth to the Moon in less than three hours. That's faster than most other nearby stars in this region of our galaxy.
I hope this information helps you learn more about the black hole discovered in the Milky Way and its characteristics.