The Early Builders: Shakti and Shiva Galaxies Together Formed the Milky Way

Monday - March 25 2024, 15:01 UTC - 8 months ago

Astronomers have identified two of the earliest building blocks of the Milky Way, Shakti and Shiva galaxies, that merged with our galaxy over 12 billion years ago. Using data from the Gaia satellite and the SDSS survey, these proto-galactic fragments were found to have similar energy and angular momentum values, providing insight into the galaxy's early formation. The results have been published in the Astrophysical Journal.

The Milky Way, home to our solar system and billions of other stars, is a complex and ever-evolving galaxy. Like many other galaxies, the Milky Way grew to its current size by merging with smaller galaxies. However, not all mergers are recent events. Astronomers have now identified what could be two of the earliest building blocks of the Milky Way, merging with our galaxy over 12 billion years ago .

These two galactic fragments, named Shakti and Shiva, were identified using data from ESA's Gaia satellite and the Sloan Digital Sky Survey (SDSS). This is a significant discovery, comparable to finding traces of an initial settlement that grew into a present-day city.When galaxies merge, several processes occur at the same time. One key event is the destabilization of the galaxies' hydrogen gas clouds, leading to the formation of new stars .

At the same time, stars from the individual galaxies begin to mingle and become part of the new, combined galaxy. However, it may still be possible to identify which stars came from which predecessor galaxies.This is where physics comes in. Stars from the same pre-merger galaxy share similar values for their energy and angular momentum, which are directly linked to the galaxy's speed and direction .

When these stars merge with stars from other galaxies, their energy and angular momentum values remain the same over time. By looking for groups of stars with similar, unusual values, astronomers can identify potential merger remnants.Other clues can also help identify the origin of a star. Stars that formed more recently generally have higher metal content compared to those formed earlier. This information, along with energy and angular momentum values, can narrow down the possible origin of a star .

The identification of Shakti and Shiva as two of the earliest building blocks of the Milky Way has provided valuable insight into our galaxy's early formation. A merger of this scale and timeline is comparable to finding the foundation of a huge metropolis. As we continue to study the Milky Way and other galaxies, we may uncover more about their past and what ultimately led to their existences as we know them today .

The result published in the Astrophysical Journal is a testament to the power of combining data from different missions and surveys. It opens up new possibilities for understanding the history of our galaxy and its role in the wider universe.