Space researchers have unveiled a novel celestial system on the Milky Way’s periphery, as part of the Kilo-Degree Exploration (KiDS). The recently identified system, termed Sextans II, appears to be an ultra-faint dwarf galaxy. These findings are documented in a manuscript issued November 10 on the pre-print repository arXiv.
The Kilo-Degree Exploration is a comprehensive multi-wavelength photometric quest utilizing the VLT Survey Telescope (VST) at the ESO’s Paranal Observatory in Chile. Commencing in 2011, this endeavor has charted 1,350 square degrees of the celestial canvas in four broad-band filters (u, g, r, i). While KiDS predominantly aims at deciphering the architecture of cosmic structures at large scales, it can also reveal dim, distant galactic collections of stars.
Consequently, a cadre of space scientists spearheaded by Massimiliano Gatto from the Astronomical Observatory of Capodimonte in Naples, Italy, set out to scour large expanses for obscure, faint stellar systems using KiDS. To this end, they sought out subdued stellar concentrations in the latest KiDS data release (DR4), uncovering tantalizing leads.
“We present the finding of a pronounced and focused accumulation of aged and metal-deficient stars within the KiDS’s exploration confines (data release 4),” the investigators recorded in the treatise.
The group pinpointed a notably alluring cluster of stars within the Sextans constellation featuring an absolute integrated brightness of -3.9. Subsequent scrutiny of this cluster through the 8.2-meter Subaru Telescope ascertained its position approximately 473,000 light-years distant.
The explorers initially named the newly discovered system KiDS-UFD-1 and later referred to it as Sextans II. The gathered intelligence suggests that Sextans II has a comparatively minor span, with a half-light radius close to 629 light-years, while its mass approximates 4,910 solar equivalents. This system exhibits a metallicity score of -1.5 dex, an ellipticity value of 0.46, and its formation dates back at least 10 billion years.
According to the treatise’s authors, the evidence suggests that Sextans II represents a dim, antiquated, and elementally impoverished configuration. The team led by Gatto deduced that this newly perceived celestial assembly is a dim spheroidal companion to the Milky Way, plausibly categorized as an ultra-faint dwarf (UFD) galaxy. Typically, UFDs are noted for their minimal luminosity, profound dark matter composition, and nascent chemical development.
Nevertheless, the investigators have not dismissed the chance that Sextans II could be a disintegrating globular cluster, stressing that more thorough analyses are imperative to validate its authenticity.
“The definitive classification of this entity will hinge on thorough spectroscopic monitoring of a substantial cohort of its constituent stars, which may pose challenges, given the spectrum of brightness these possible red giant branch members span,” the authors penned.
Further details:
Massimiliano Gatto et al, New Kids in Town. Sextans~II: a fresh stellary array on the outskirts of the Milky Way, arXiv (2023). DOI: 10.48550/arxiv.2311.06037
Periodical reference:
arXiv
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Reference:
Progeny in the Firmament: Novel Astral System Detected by the Kilo-Degree Exploration (2023, November 25)
accessed 25 November 2023
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