Discovering the Building Blocks of the Milky Way: An Inside Look

When it comes to space exploration, there are numerous branches of science that make up this application area. One of those branches is astrophysics, which seeks to understand the physical properties and behavior of celestial objects and phenomena using the principles of physics. Astrophysicists study astronomical objects, such as galaxies, black holes, stars, and planets, and try to figure out how certain phenomena influence their evolution, formation, and behavior.

Astrophysicists utilize a wide range of tools and spectroscopic techniques in their work, including observational data from telescopes, theoretical models, computational simulations, and experimental studies, to investigate and explain the fundamental principles underlying the structure and dynamics of the cosmos. For studies of galaxy formation astrophysicists use optical spectroscopy to analyze visible light emissions and infrared spectroscopy to study obscured regions, providing insights into properties like chemical composition, star formation rates, and the dynamics of galaxies.

Recently, astronomers identified two streams of stars that could help explain the formation of the universe. Named after the Hindu deities Shakti and Shiva, these two clusters of stars were discovered to be two building blocks for the Milky Way galaxy (1). Shakti and Shiva contain stars that have similar chemical compositions in stars that existed 12–13 billion years ago, and they are currently approximately 30,000 light years away from the center (1). The research team, led by Khyati Malhan, utilized data from Gaia Data Release 3 and spectroscopy to analyze Shakti and Shiva (2). The findings of their study were published in The Astrophysical Journal.

View from space to a spiral galaxy and stars. Universe filled with stars, nebula and galaxy. Elements of this image furnished by NASA. Image Credit: © Tryfonov - stock.adobe.com

The Milky Way Galaxy was formed as a byproduct of the Big Bang that occurred approximately 13.8 billion years ago (1). It is the home of eight planets orbiting the Sun, a medium-sized stars, and is known for its swirling arms containing other stars and nebula. Understanding the formation of the Milky Way galaxy could help astronomers expand their knowledge of the origin of the universe, including the formation of other celestial bodies.

Read More: How NASA Scientists are Using Spectroscopy to Study Exoplanets

The researchers’ long-term goal with the findings of their study is to essentially create a story of the universe, tracing its formation and evolution from the Big Bang to modern day. To that end, the researchers determined that both Shakti and Shiva exhibit characteristics indicative of an accreted origin in terms of their orbit-space distribution, but their abundance patterns suggest attributes typically associated with an in situ population (2). This apparent contradiction may be explained by interpreting the abundance patterns because of rapid enrichment (2).

From using Gaia Data Release 3 astrometry and spectroscopy, the researchers proposed two theories to explain how Shakti and Shiva formed. The first proposal was that Shakti and Shiva were formed by resonant orbit trapping induced by the rotating bar of the Milky Way (2). The second theory is that Shakti and Shiva were protogalactic fragments that rapidly formed stars and coalesced early in the galaxy's history (2). These substructures are located on prograde orbits inside the solar circle and have significant stellar masses, indicating their importance in understanding the dynamics and formation history of the Milky Way (2).

In conclusion, this study builds upon previous studies using Gaia data and spectroscopy to analyze populations of stars that formed around the beginning of the universe in order to better understand the Milky Way’s formation.

Author’s Note: The James Webb Space Telescope (JWST) is helping to rewrite the original theories associated with our understanding of time, the Big Bang, and galaxy formation. We encourage readers to investigate these new findings (3–5).

References

(1) Dunham, W. Scientists identify Milky Way's ancient building blocks Shakti and Shiva. Reuters. Available at: https://www.reuters.com/science/scientists-identify-milky-ways-ancient-building-blocks-shakti-shiva-2024-03-22/ (accessed 2024-03-26).

(2) Malhan, K.; Rix, H.-W. Shiva and Shakti: Presumed Proto-Galactic Fragments in the Inner Milky Way. Astrophys. J. 2024, 964 (2), 104. DOI: 10.3847/1538-4357/ad1885

(3) Mann, A. The James Webb Space Telescope Prompts a Rethink of How Galaxies Form. Proc. Natl. Acad. Sci. U.S.A. 2023, 120 (32), e2311963120. DOI: 10.1073/pnas.2311963120

(4) Kohut, P. The Unity Principle-The Key to Explaining Shocking James Webb Telescope Observations. J. Mat. Sci. Apl. Eng. 2024, 3 (1), 01 5. https://www.mkscienceset.com/articles_file/278-_article1707919458.pdf (accessed 2024-03-24).

(5) Stann, E. Astronomers Suggest More Galaxies Were Formed in the Early Universe Than Previously Thought. Phys.org. Home Page. https://phys.org/news/2023-01-astronomers-galaxies-early-universe-previously.html (accessed 2024-03-24).