Astronomers discover remains of Loki galaxy swallowed by the Milky Way

An international team of astronomers has identified 20 ancient stars that share similar chemical and orbital characteristics, suggesting they all originated from a dwarf galaxy that researchers have dubbed “Loki.” Scientists believe that this small galaxy was absorbed by Via Láctea billions of years ago during the formation process of our galaxy. The study was published in the journal Monthly Notices of the Royal Astronomical Society.

The research represents a significant advance in understanding how galaxies form and grow. “We may have detected one of several small systems that contributed to the formation of our Via Láctea,” said Federico Sestito, postdoctoral research astronomer at Universidade of Hertfordshire and co-author of the study.

Identificação through chemical and orbital characteristics

The detection of stars of common origin depended on a combination of advanced methodologies. The researchers used high-resolution spectroscopy, orbital motion analysis and theoretical simulations to interpret the properties of the 20 stars. Chemical measurements proved to be essential for advancing research, offering data that previous studies did not have.

“In the past, we had to observe these ancient stars with peculiar movements; however, we did not have chemical information, which is now available with this work,” explained Sestito. Researchers analyzed samples of:

• Elementary Composição of stars (especially metallicity levels)
• Velocidade and orbital trajectory in the galactic disk
• Assinaturas Heavy Element Spectrographs
• Simulações comparisons with galactic halos and dwarf galaxies

The metal poverty of the 20 stars confirmed that they formed very early in the universe. Essas primordial stars contain only traces of heavier elements such as iron, clear evidence of their origin at an earlier time. The stars’ unique positioning close to Via Láctea’s disk — where younger, metal-rich stars typically inhabit — provided a second strong indicator of their common origin.

Dinâmica absorption of dwarf galaxies

Via Láctea did not emerge in isolation. Over billions of years, our galaxy absorbed multiple smaller galaxies, incorporating their stars and structure into the formation of today’s galactic system. The identification of Loki contributes to mapping this complex process of galaxy merger and growth.

Chemical analyzes revealed that the 20 stars were enriched by specific violent processes. The team detected signatures of high-energy supernovae, hypernovae, rapidly rotating massive stars and neutron star mergers. Notavelmente, found no evidence of white dwarf explosions. Essa’s absence indicates that Loki was likely a “short-lived energetic dwarf galaxy” characterized by intense and rapid star formation.

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Desafios in detecting hidden galaxies

Identificar old galaxies within Via Láctea present significant difficulties. While Embora is relatively simple to locate small fragmented and accumulated galaxies on the outskirts of our galaxy, finding them in the central disk is a considerably more difficult task. The disk is densely populated with billions of younger stars with similar chemical composition, making selection and mapping extremely laborious.

Sestito highlights the scientific importance of this research to understand fundamental processes. “The most metal-poor stars in our galaxy, which are also among the oldest, are extremely important celestial objects. Elas could open a window into the early processes related to the formation of Via Láctea, the origin of the elements and the properties of the first stars,” said the astronomer.

Muitas other ancient galaxies like Loki may remain hidden in the vicinity of Via Láctea, still awaiting identification. The Sestito team’s current work focuses on the systematic search for these primordial systems that shaped our galaxy.

Perspectivas Futures for Observational Astronomy

The coming years will promote technological advances that will dramatically expand detection capabilities. Novas multi-object spectroscopic facilities will provide chemical data from thousands of stars simultaneously, overcoming current observation limitations.

“Although this work may be limited by the number of stars observed, the future looks promising. Teremos multi-object spectroscopic facilities that will obtain chemical information from thousands of stars,” predicted Sestito. With this larger volume of data, astronomers will be able to identify multiple ancestral stellar populations and accurately map the primordial components that formed Via Láctea. Detailed understanding of these ancient dwarf galaxies will contribute to more accurate models of galactic evolution and the history of the early universe.