European astronomers have made an intriguing discovery regarding a recently detected black hole named Gaia BH3. According to their findings, Gaia BH3 is closely linked to a nearby disrupted star cluster called ED-2. The research, published on the preprint server arXiv on April 17, sheds light on the nature and origins of these celestial entities.

Gaia BH3, situated approximately 1,900 light years away, was discovered in April 2024. This black hole is part of a wide binary system within the galactic halo and boasts a staggering mass of around 33 solar masses. In fact, it is now recognized as the most massive black hole stemming from stellar origins within our galaxy. The black hole's companion is a considerably larger, aging giant star with a mass of approximately 0.76 solar masses, making it around five times larger than the sun. The binary system consisting of Gaia BH3 and its companion has an orbital period of 11.6 years.

ED-2, on the other hand, was once an old star cluster that has now become a galactic halo stellar stream. Remarkably, this dynamically cold stream passes through our solar neighborhood. The stars in ED-2 possess an average metallicity level estimated at -2.60.

Eduardo Balbinot, leading a team of astronomers from the University of Groningen in the Netherlands, delved further into the chemical properties of the member stars in ED-2, as well as the orbital characteristics of the Gaia BH3 binary. Their investigations revealed an intriguing connection: Gaia BH3 is undoubtedly a part of the ED-2 stellar stream.

The researchers stated in their paper, "We find that the galactic orbit of the Gaia BH3 system and its metallicity are entirely consistent with being part of the ED-2 stream." The study also revealed that Gaia BH3's orbit around the galaxy is indistinguishable from that of the member stars of the ED-2 stream. Surprisingly, only 17% of the ED-2 members are positioned closer to the galactic center than Gaia BH3.

Moreover, the chemical composition of the giant star in Gaia BH3, with a mean metallicity of -2.56, closely aligns with the mean metallicity level of stars in ED-2. An examination of chemical elemental abundances, including magnesium, europium, and barium-to-iron ratios, further supports the association between Gaia BH3 and its companion.

These findings thus confirm the unquestionable correlation between Gaia BH3 and the ED-2 stream, as stated by the authors.

In addition to the association between these celestial entities, the gathered data has shed new light on the formation of Gaia BH3 and ED-2. The results suggest that Gaia BH3's progenitor formed over 13 billion years ago, while the parent system of ED-2 constituted a smaller cluster with a mass less than 42,000 solar masses.

The researchers concluded, "This implies that the black hole could have formed directly from the collapse of a massive very-metal-poor star, but that the alternative scenario of binary interactions inside the cluster environment also deserves to be explored."

These remarkable findings pave the way for further explorations into the origins and evolution of black holes and disrupted star clusters. As scientists continue to delve into the mysteries of the universe, each new discovery brings us closer to unveiling the secrets of our cosmic surroundings.

Reference:
E. Balbinot et al, The 33 M⊙ black hole Gaia BH3 is part of the disrupted ED-2 star cluster, arXiv (2024). DOI: 10.48550/arxiv.2404.11604