Shiva, Shakti in Milky Way galaxy? Here's what scientists have found

The astrophysicist examined two new substructures, Shiva and Shakti, in the orbit-metallicity space of the inner Milky Way using Gaia DR3 spectroscopy and astrometry.

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Courtesy: X (Khyati Malhan)

Scientists have discovered two objects and have called them ‘Shiva’ and ‘Shakti,’ which may be among of the Milky Way's oldest ‘building blocks.’ According to Dr Khyati Malhan and Hans-Walter Rix of the Max Planck Institute for Astronomy, Shiv and Shakti, that are names after Hindu deities are thought to be the remains of two galaxies that combined with an early Milky Way between 12 and 13 billion years ago, helping our home galaxy grow at first.

How The Oldest ‘Building Blocks’ Have Been Identified?

According to the official post, the astrophysicist examined two new substructures, Shiva and Shakti, in the orbit-metallicity space of the inner Milky Way using Gaia DR3 spectroscopy and astrometry. Two limited, high contrast over densities were recognized in the (Lz,E) distribution of metal-poor (−2.5<[M/H]<−1.0) and brilliant (G<16) stars. 

As per study, either these prograde substructures were created by some form of resonant orbit trapping of the field stars by the rotating bar; a plausible scenario proposed by Dillamore et al. (2023). Or, Shakti and Shiva were proto-galactic fragments that formed stars rapidly and coalesced early, akin to the constituents of the Poor Old Heart of the Milky Way; just less deep in the Galactic potential and still discernible in orbit space.

The study further says that Shiva and Shakti are located close to the center of the Milky Way, and each stream is thought to contain the mass of roughly ten million suns. Because of the ancient stars' identical ages, orbits, and compositions, astronomers were able to conclude that both streams were probably remnants of an external source that eventually merged to form the Milky Way.

The Gaia Space Telescope

The European Space Agency launched the Gaia space telescope in 2013, and it started surveying the universe the following year. By using Gaia's data, astronomers have been able to put together the history of the galaxy by finding previously undiscovered structures in the Milky Way. Astronomers now have access to the locations, distances, and motions of about two billion stars in the galaxy thanks to the telescope's collection.

During their "galactic archaeology" studies in 2022, study coauthor Hans-Walter Rix and his colleagues utilized Gaia to look into the center of the Milky Way and uncovered the oldest stars yet discovered in the galaxy. Two streams that seemed to stand out from the almost 6 million stars that Gaia and the Sloan Digital Sky Survey saw were identified through data processing.