The existence of black holes has been proposed in the early 20th century as a resolution to the general relativity theory of Albert Einstein. But it was not until the mid-20th century that astronomers started finding black holes using indirect methods that involved observing surrounding objects and space.
Since the 1980s, scientists have studied the different types of black holes, particularly supermassive black holes (SMBHs). These observations gave them an opportunity to test the laws of physics. A new study from a team of international astronomers described a sun-like star with strange orbital characteristics, which is part of a black hole binary system.
Discovery of the Nearest Black Hole to Earth Implies Existence of Many Others in the Galaxy
Nearest Black Hole to the Solar System
According to Phys.org, the team relied on data from the Gaia Observatory of the European Space Agency (ESA) to observe the sun-like star with strange orbital characteristics.
They spent nearly a decade measuring the positions, distances, and motions of almost 1 billion cosmic objects, including comets, stars, asteroids, and galaxies. The Gaia mission aims to construct the most accurate 3D space catalog ever and so astronomers tracked every movement of objects as they orbit the center of the Milky Way galaxy.
Based on the study "A Sun-like star orbiting a black hole," astronomers examined 168,065 stars in the Gaia Data Release 3 (GDR3) that have two-body orbits and found a promising candidate. The G-type star called Gaia DR3 4373465352415301632 or Gaia BH1 is determined to have a binary black hole binary companion, given the size of the orbit and the mass of its unseen companion, which is about 10 solar masses.
Kareem El-Badry, a Harvard Society Fellow astrophysicist, said that they confirmed the Gaia solution is correct and ruled out other non-black hole alternatives by observing the star with several telescopes to analyze radial velocity measurements. These observations convinced them that the sun-like star is indeed orbiting a nearby black hole.
These methods were also used for hunting exoplanets, which allowed astronomers to observe and measure the gravitational forces influencing Gaia BH1's orbit. El-Badry indicated that these findings could point to the first black hole observed in the Milky Way galaxy without observing its X-ray emissions or other energetic releases.
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Finding Black Holes in the Milky Way Galaxy
The Milky Way galaxy is thought to have hundreds of millions of black holes, but only a few dozen have been revealed so far through detecting their X-ray emissions. According to Science, the newly found black hole could be the nearest to the Solar System, which is only about 1,000 light-years away from Earth.
In fact, it is even visible to the naked eye. Todd Thompson, an astronomer at Ohio State University, commented that the team of astronomers who conducted the study has good evidence to support their claim.
The invisible nature of black holes usually frustrates astronomers; but recent findings of several naked, non-accreting candidates using a technique employed in detecting exoplanets give them hope of finding more.
El-Badry and his colleagues are excited about the Gaia Data Release 4 (GDR 4), which could include all data gathered during the 4 mission. It will most likely have the most updated astrometric, photometric, and radial-velocity catalogs of all cosmic objects observed. The fifth mission, GDR 5, will include the nominal and extended missions. The team is confident that it will reveal dozens of similar systems, like the Gaia BH1.
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