A secret may be hidden in the hearts of the fluffy star clusters that spread across the sky. A swarm of more than 100 stellar masses. black hole.
The star cluster in question is called Palomar 5. This is a star stream that stretches over 30,000 light-years and is located about 80,000 light-years away.
Globular clusters like this are often thought of as “fossils” of the early universe. They are very dense, spherical, and typically contain about 100,000 to 1 million very old stars. some, Like NGC 6397almost as old as the universe itself.
In any globular cluster, all its stars formed at the same time from the same gas cloud. There are over 150 known objects in the Milky Way globular cluster;These objects are e.g. history of the universe,or dark matter content The galaxy they orbit.
But there’s another type of star group that’s getting more attention. It is a tide, a long river of stars across the sky.
Previously, these were difficult to identify, but thanks to the Gaia Space Observatory, mapped data See more of the Milky Way in 3D with high precision these flows has been came to light.
Watch the video below for an overview of the findings.
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“We don’t know how these streams form, but one idea is that the star cluster collapsed,” said Marc Giles, an astrophysicist at the University of Barcelona in Spain. Explained in 2021 When researchers first announced their detection.
“However, we cannot be sure because the recently discovered streams do not have star clusters associated with them.
“Therefore, to understand how these streams formed, we need to study the stars that contain the star systems associated with them. Palomar 5 is a unique case, making it a Rosetta Stone for understanding stream formation, which is why we studied it in detail.”
Palomar 5 looks unique in that it has both a very wide and loose distribution of stars and a long tidal current that spans more than 20 degrees of the sky, so that’s what Gierres and his team focused on.
The researchers used detailed N-body simulations to reconstruct the orbits and evolution of each star in the cluster to see how they got to where they are today.
Recent evidence suggests that group of black holes It is possible that it exists in the central region of a globular cluster, and gravitational interactions with black holes are known. push the stars awayscientists included a black hole as part of the simulation.
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Their results showed that the population of stellar-mass black holes within Palomar 5 could have resulted in the configuration we see today. Orbital interactions can cause stars to fly out of the cluster and into the currents, but only if the number of black holes is much larger than predicted.
Stars escaping from clusters more efficiently and easily than black holes would have changed the black hole proportion, increasing it considerably.
“The number of black holes is approximately three times higher than expected based on the number of stars in the cluster, meaning that more than 20 percent of the total mass of the cluster is made up of black holes.” Giles said..
“They each have about 20 times the mass of the Sun and were formed in a supernova at the end of the life of a massive star, when the cluster was still very young.”
According to the research team’s simulations, this star cluster will completely disappear in about 1 billion years. Just before this happens, what remains of this cluster consists entirely of black holes, orbiting the center of the galaxy. This suggests that Palomar 5 is nothing special after all, and like everything else we’ve discovered, it will completely dissolve into the stellar stream.
It also suggests that other globular clusters are likely to eventually suffer the same fate. And it confirms that globular clusters may be the perfect place to look for black holes that eventually collide, or for an elusive class of black holes. intermediate black holebetween a stellar-mass lightweight and a supermassive heavyweight.
Related: Hear the sound of a black hole ‘kicking’ the universe in an astonishing first audio source
“Most of the binaries are black hole Mergers form within star clusters. ” Astrophysicist Fabio Antonini said: He holds a Ph.D. from Cardiff University, UK.
“The big unknown in this scenario is how many black holes there are in a star cluster, which is hard to constrain observationally because black holes are invisible. Our method provides a way to find out how many black holes there are in a star cluster by observing the stars they emit.”
This study natural astronomy.
A previous version of this article was published in July 2021.