A few thousand light-years away from Earth, there is a large extraterrestrial object that is traveling alone across our galaxy. Even though it’s not so enormous, its mass is more than that of our sun. Astronomers have a hunch that it might be the first solitary black hole in the Milky Way to be discovered to have a mass comparable to that of our sun. Alternately, it could turn out to be one of the neutron stars with the greatest mass.
This wanderer was first seen in 2011. It wasn’t seen. Instead, astronomers discovered it when its gravity momentarily amplified the light of a more distant star. Back then, nobody knew for certain what it was. Now, two groups of astronomers have reviewed Hubble Space Telescope photos. They are still uncertain as to what the heavy item is, but they have cut down the possibilities.
One group hypothesizes that this strange outlier is a seven-times-massive black hole. “We report the first unequivocal observation and mass measurement of an isolated stellar-mass black hole,” its 94 authors write. They discuss it in an upcoming publication.
Not so fast, argues another 45-person scientific team. They estimate that it weighs just two to four times as much as our closest star. If true, this would make it a black hole with an extraordinarily low mass or a neutron star with an oddly high mass. This organization will publish their results in a forthcoming issue.
Neutron stars and stellar-mass black holes may emerge when huge stars with at least several times the mass of the sun collapse due to their own gravity. This occurs toward the conclusion of the lifetimes of these stars. Astronomers currently think that around a billion neutron stars and approximately 100 million black holes of stellar-mass lurk inside our galaxy.
Both of these sorts of items are difficult to detect. Neutron stars are minuscule, being about the size of a city. In addition, they emit minimal light. Regardless of their size, black holes produce no light. To discover these items, scientists often study their effects on the surrounding environment.
Kailash Sahu argues, “The only way we can detect them is if they impact something else.” He is an astronomer at Maryland’s Space Telescope Science Institute.
The enormous mystery
Scientists have discovered roughly two dozen stellar-mass black holes to far. (These are small in comparison to their supermassive counterparts, which reside at the core of the majority of galaxies, including our own.) These relatively small black holes were discovered by analyzing changes in their neighbors. A black hole and a regular star will spiral together on occasion. Imagine it as a dance.
However, this is a risky dance, since the black hole pulls stuff from the companion star. As the material of the star descends into the black hole, X-rays are emitted. Planetary orbiting telescopes can detect this radiation. Scientists will have difficulty determining the size of a black hole before it devoured a star. And because a black hole’s mass is a defining property, seeing black holes that consume stars might cause confusion. “If we want to understand the characteristics of black holes, it’s essential to identify solitary ones,” Sahu explains, referring to the new lonesome black hole.
Researchers have been searching the sky for such solitary black holes for more than a decade. Scientists have searched for warped starlight in an attempt to detect these outlaws.
According to Einstein’s theory of general relativity, the gravity of any huge object, even an unseen one, would distort the space in its vicinity. This bending amplifies and distorts the background starlight. This phenomenon is termed gravitational lensing by astronomers. By detecting variations in the brightness and apparent location of stars, astronomers may determine the mass of a lens-like moving object. This approach has already uncovered many exoplanets.
In 2011, scientists reported the discovery of a star that suddenly became more than 200 times brighter. Observations done using telescopes in Chile and New Zealand were unable to determine if the apparent location of the star was also shifting. And this knowledge would be crucial for determining the mass of the lens-like item. If the object is massive, its gravity would warp space to the point that the star would seem to move. Even a “huge” alteration in the star’s location would have been very minute and difficult to detect. And it is difficult to see tiny features in photos acquired by terrestrial telescopes. (The chaotic atmosphere of our planet just obscures them.)
To circumvent this issue, two separate groups of astronomers resorted to Hubble. This telescope, which orbits well above the upper atmosphere, can catch very detailed photos. Both groups discovered that the position of the star varied over many years.
The team lead by Sahu now believes the apparent motion of the star was caused by an object about seven times as massive as the sun. Such a huge star should have shown very bright in the Hubble photos. However, researchers saw nothing. The team now assumes that the unknown object must be a black hole since it is so dense and dark.
Casey Lam, an astronomer, led a group of researchers to a different conclusion. Lam is employed at Berkeley University of California. She and her colleagues determined that the lensing item had a lesser mass. It was perhaps two to four times the size of our sun. In such a scenario, they said, it may be a black hole or a neutron star.
Jessica Lu of Berkeley thinks it’s a fascinating item. Lam’s teammate. Lu thinks the unidentified item is either a huge neutron star or a small black hole. It’s in the ‘mass gap’
Will M. Farrar states that the new findings are exciting from any angle. He is an astronomer from Recent York’s Stony Brook University who did not participate in either of the two new analyses. Working “in the vanguard of what is quantifiable” is tremendously exciting, according to him.