The Gaia space telescope made a groundbreaking discovery, finding two ancient streams of stars named Shakti and Shiva, which played a crucial role in the formation and evolution of our Galaxy over 12 billion years ago.
Shakti and Shiva, named after Hindu deities, are remnants of two galaxies that merged with the Milky Way during the early stages of the formation of the first galaxies in the universe. What makes these streams unique is their age, having formed long before the most ancient parts of spiral arms and the central disk of the Milky Way.
Utilizing data from the GAIA telescope, scientists were able to observe these ancient structures, a feat in itself. The changing nature of the Milky Way over the lifespan of these stars made it challenging to identify them as a cohesive group, but Gaia made it possible.
These star streams, located near the core of the Milky Way, offer astronomers a glimpse into the early days of our galaxy and the evolution of large-scale galaxies in the Universe. Each stream is estimated to have a mass of around 10 million suns, with stars in Shakti and Shiva sharing similar ages, orbital paths, and compositions, indicating their external origin and integration into the Milky Way. Studying Shakti and Shiva provides scientists with deeper insights into how the initially small Milky Way transformed into the vast collection of stars we see today.