Scientists have uncovered what could be the earliest building blocks of our Milky Way galaxy, and they've given them the names "Shiva" and "Shakti."
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Recently, the Max Planck Institute for Astronomy shared exciting news about the discovery of what might be the Milky Way's earliest building blocks, known as "Shiva" and "Shakti." These remnants are believed to stem from two galaxies that merged with an earlier version of our Milky Way around 12 to 13 billion years ago, contributing to its growth.
Astronomers, drawing data from the European Space Agency's Gaia satellite and the SDSS survey, christened these components Shiva and Shakti. It's akin to uncovering traces of a foundational settlement that eventually evolved into a bustling metropolis, albeit on a cosmic scale.
Galactic collisions and mergers set a series of events in motion. Each galaxy brings its own hydrogen gas reservoir, and when they collide, these clouds become unstable, leading to the formation of numerous new stars. Prior to the collision, each galaxy hosts its own set of stars, and these "accreted stars" only represent a portion of the newly combined galaxy's stellar population. The challenge lies in distinguishing which stars originated from which precursor galaxy after the merger.
However, fundamental physics provides valuable clues. During galactic collisions, as stars mingle, most retain certain properties linked to their original galaxy's speed and direction. Stars from the same precursor galaxies exhibit similar values of energy and angular momentum, which are conserved within a galaxy's gravitational field.
In their quest, astronomers utilized Gaia data along with detailed stellar spectra from the Sloan Digital Sky Survey. This combination offered insights into the stars' chemical compositions. "We noticed that, among a specific range of metal-poor stars, there were clusters around two particular combinations of energy and angular momentum," explained researcher Khyati Malhan.
Malhan, who named the constituent galaxies Shiva and Shakti, remarked, "Shiva and Shakti might represent the earliest additions to the core of our Milky Way, setting the stage for its transformation into a larger galaxy." This discovery sheds light on the ancient origins of our cosmic home.
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