Researchers at the Max Planck Institute for Astronomy have identified what might be the earliest components of the Milky Way galaxy, naming them "Shiva" and "Shakti."
These remnants are believed to have originated from two galaxies that merged with an earlier version of the Milky Way over 12 to 13 billion years ago, playing a pivotal role in its formation and expansion.
Researchers at the institute have christened these elements Shakti and Shiva -- a female cosmic force, often deemed a consort of Shiva, and the latter a Hindu deity with the ultimate destructive force.
Researchers synthesised information from the European Space Agency's Gaia satellite and the SDSS (Sloan Digital Sky Survey) for their findings.
The discovery involved uncovering remnants of a founding settlement that evolved into a metropolitan city, albeit on a cosmic magnitude.
According to researchers, galactic collisions and mergers set various processes into motion. As galaxies converged, their individual reservoirs of hydrogen gas become destabilised, leading to the formation of numerous new stars. Prior to the collision, each galaxy harbours its own set of stars.
The combined galaxy boasts a blend of both original and newly formed stars. The challenge lay in discerning the origins of specific stars—determining which ones belonged to each predecessor galaxy once the merger is complete.
Researchers distinguished the older stars from new studying the angular momentum – the momentum associated with orbital motion or rotation.
"For stars moving in a galaxy’s gravitational field, both energy and angular momentum are conserved: they remain the same over time. Look for large groups of stars with similar, unusual values for energy and angular momentum – and chances are, you might find a merger remnant," they said in a press release issued on March 21.
In their investigation, astronomers analysed data from the Gaia satellite along with stellar spectra data from the SDSS. The SDSS offered intricate insights into the chemical compositions of the stars.
Khyati Malhan, one of the two researchers, said, "We noticed that, among a certain group of metal-poor stars, there was a clustering around two distinct combinations of energy and angular momentum."
"We noticed that within a specific range of metal-poor stars, there was a clustering around two particular combinations of energy and angular momentum," she said.
Malhan was the one who dubbed the two merging galaxies Shiva and Shakti.
She added, "Shakti and Shiva could be the initial building blocks of our Milky Way's core, kickstarting its expansion into a larger galaxy."
Hans-Walter-Rix, the other researcher, said, "Shakti and Shiva might be the first two additions to the ‘poor old heart’ of our Milky Way, initiating its growth towards a large galaxy."
