Astronomers may have discovered that the closest black holes to Earth could be lurking in the Hyades Cluster, located only about 150 light-years from the Sun.
In fact, these black holes may have been ejected from the dense star cluster millions of years ago to wander the galaxy alone. However, they will still be ten times closer than the black hole that was previously considered the closest to Earth.
The Hyades appears in the constellation Taurus, an open cluster of hundreds of stars. Open clusters like these are groups of stars that are thought to have formed at the same time from the same massive cloud of gas and dust. For this reason, stars in this type of cluster are known to share basic characteristics such as chemical composition and ages.
In order to discover what could be the closest black holes to our planet, a team led by Stefano Torniamenti, a postdoctoral researcher at the University of Padua, created simulations of the motions and evolutions of stars in the Hyades. The simulation was also created using the black holes in the equation. The scientists then compared the results of these simulations with actual observations made previously of the velocities and positions of open star clusters. The latest data set is owed to the Gaia space telescope.
“Our simulations cannot simultaneously match the mass and volume of the Hyades unless some black holes were present at the center of the cluster today, or until recently.” He said in a statement.
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Torniamenti and his colleagues found that the models that best fit observations of the Hyades are those that include two or three black holes within the star cluster. Beyond that, simulations that included star cluster black holes that were theoretically ejected no more than 150 million years ago also matched the Gaia data.
This is because, the team says, if those black holes had been violently ejected from the Hyades when the cluster was about a quarter of its current age — about 625 million years — the star cluster would not have evolved enough to remove evidence of its existence. their previous existence.
The researchers explain that even if black holes were ejected from the Hyades by now, they would still be the closest black holes to Earth despite their rogue status. This is according to simulations that indicate that if black holes are not currently located in the Hyades, they are still nearby.
The previous holders of the closest black hole to Earth were Gaia BH1 and Gaia BH2, which, as their names suggest, were discovered by Gaia data this year only.
Gaia BH1 is located 1,560 light-years from Earth, while Gaia BH2 is located about 3,800 light-years away. Although this means that both black holes are in Earth’s backyard (in cosmic terms, at least), they are still more than 10 to 20 times away from the Hyades cluster and a possible pair or trio of black holes.
This new research and the previous discovery of Gaia BH1 and BH2 exemplify how Gaia, which launched in 2013, has reshaped astronomy. The space telescope allowed astronomers to study the positions and velocities of individual stars in groups such as the Hyades for the first time.
Gaia is able to achieve such breakthroughs because it can precisely measure the positions and movements of billions of stars against the background sky. Tracking stellar movements with such high precision helps reveal the gravitational influences that attract these stars, even if this influence comes from hidden objects such as black holes with a small stellar mass.
“This observation helps us understand how the presence of black holes affects the evolution of star clusters,” said lead author and researcher at the University of Barcelona, Marc Giles. “These results also give us insight into how these mysterious objects are distributed across the galaxy.”
The team’s research was published in June in the journal Monthly Notices of the Royal Astronomical Society.
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