Researchers explore the properties of globular cluster NGC 6355

A world staff of astronomers has carried out a chrono-chemodynamical evaluation of a Galactic globular cluster generally known as NGC 6355. Outcomes of the examine, introduced in a paper printed January 12 on the arXiv preprint server, ship necessary insights into the properties and chemical composition of this cluster.

Globular clusters (GCs) are collections of tightly certain stars orbiting galaxies. Astronomers understand them as pure laboratories enabling research on the evolution of stars and galaxies. Particularly, globular clusters may assist researchers higher perceive the formation historical past and evolution of early sort galaxies, because the origin of GCs appears to be carefully linked to durations of intense star formation.

At a distance of some 28,300 light years away from the Earth, NGC 6355 (also referred to as GCl-63 or ESO 519-SC15) is a globular cluster within the constellation Ophiuchus. It’s a well-known cluster that has been studied because the 1900s. Earlier observations of NGC 6355 have discovered that it has a comparatively excessive mass of about 101,000 solar masses, reddening at a stage of 0.82 and its metallicity is roughly -1.46. Absolutely the age of the cluster is estimated to be 13.2 billion years.

Not too long ago, a gaggle of astronomers led by Stefano O. Souza of the College of São Paulo in Brazil, has investigated NGC 6355 with the principle goal of shedding extra mild on its historical past and properties.

“Within the current work, we mix the chemical info with photometric and dynamical properties of the cluster to constrain its historical past. The chemical information relies on the UVES spectrograph (Dekker et al, 2000) in FLAMES-UVES mode on the ESO-VLT, the photometry on HST information, and the dynamical properties are supplied by orbital integration using the McMillan (2017) Galactic potential,” the researchers defined.

Typically, the staff analyzed the globular cluster NGC 6355 within the context of the evolution of the Galactic bulge. They carried out a deep and cautious evaluation, together with photometry, chemical abundances, and dynamics.

The examine discovered that NGC 6355 has a metallicity of −1.39, which confirms that it is among the most metal-poor clusters of the Galactic bulge. The imply abundance ratio of alpha parts to iron of NGC 6355 was measured to be 0.37, suggesting an enrichment from Sort II supernovae. All in all, the astronomers concluded that the abundance sample of NGC 6355 is appropriate with bulge discipline RR Lyrae stars and in-situ well-studied GCs.

The analysis confirmed that NGC 6355 is about 13.2 billion years outdated and refined its distance because it turned out that the cluster is nearer than beforehand thought—roughly 27,800 mild years away. Furthermore, the orbital parameters of NGC 6355 and its extinction coefficient at a stage of two.84, point out that the cluster is at present confined throughout the Galactic bulge quantity.

The authors of the paper concluded that this GC appears to have originated from the main-bulge progenitor, with a low likelihood of an ex-situ origin; nonetheless, extra spectroscopic information of the cluster stars are required with a purpose to affirm this.

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