Shakti & Shiva: Building blocks of the Milky Way

In a recent study published in The Astrophysical Journal, astronomers from the Max Planck Institute for Astronomy, Germany, have identified the earliest “building blocks” of our Milky Way galaxy, dating back 12-13 billion years. These stellar groups, named ‘Shakti‘ and ‘Shiva’, provide insights into the galaxy‘s formation, akin to discovering traces of an initial settlement that grew into a large present-day city.

Shakti and Shiva: The Early Ancestors of the Milky Way

The researchers analyzed stellar datasets, finding that stars from merging galaxies were crowded around two specific signatures of energy and angular momentum. These stars, forming ‘Shakti’ and ‘Shiva’, retained basic properties linked to their origin galaxies’ speed and direction.

The study’s co-author, Khyati Malhan, named these structures after Hindu deities, with Shiva representing one of the principal deities of Hinduism, and Shakti symbolizing a female cosmic force often portrayed as Shiva’s consort.

The stars in ‘Shakti’ and ‘Shiva’ were found to have a higher angular momentum compared to those at the heart of the Milky Way, suggesting they belonged to separate galaxies that merged with our own. Additionally, these stars were low in metal content, indicating they were formed a long time ago. Stars with higher metal content are typically formed more recently.

Implications of the Discovery

The researchers believe that ‘Shakti’ and ‘Shiva’ might be the first two additions to the heart of the Milky Way, initiating its growth towards becoming a large galaxy. This discovery sheds light on the galaxy’s formation process, highlighting the merging of smaller galaxies as a key mechanism in creating the Milky Way’s structure.

For their analysis, the researchers utilized data from the European Space Agency’s Gaia satellite, combined with stellar datasets from the US Sloan Digital Sky Survey. Gaia’s dataset, launched in 2013, includes information about the positions, changes in positions, and distances of almost 1.5 billion stars within our galaxy, providing valuable insights for this study.

The identification of ‘Shakti’ and ‘Shiva’ as some of the earliest ancestors of the Milky Way opens up new avenues for understanding the galaxy’s formation and evolution. This discovery marks a significant milestone in our quest to unravel the mysteries of the universe and our place within it.

(With inputs from PTI)

Harry Byrne

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