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xxxx Scientists have discovered what could be the Milky Way’s earliest building blocks and named them “Shiva” and Shakti.”

 CNN — 

Astronomers have used the Gaia space telescope to spy some of the first building blocks of the Milky Way galaxy: two ancient streams of stars named Shakti and Shiva that helped our home galaxy grow and evolve more than 12 billion years ago.

Named after Hindu deities, the star streams appear to be the remnants of two galaxies that merged with an early version of the Milky Way between 12 billion and 13 billion years ago when the first galaxies were forming across the cosmos. The structures are so old that they formed well before the most ancient parts of the Milky Way’s iconic spiral arms and central disk.

A study detailing the observations appeared Thursday in The Astrophysical Journal.

“What’s truly amazing is that we can detect these ancient structures at all,” said lead study author Dr. Khyati Malhan, postdoctoral scholar and Humboldt Research Fellow at Stockholm University in Sweden, in a statement. “The Milky Way has changed so significantly since these stars were born that we wouldn’t expect to recognise them so clearly as a group — but the unprecedented data we’re getting from Gaia made it possible.”

Observing Shakti and Shiva’s stellar wonders could help astronomers unlock the secrets of the Milky Way galaxy’s earliest days and the evolution of similarly massive galaxies throughout the cosmos, according to the researchers.

‘The first steps of our galaxy’s growth’

The Gaia space telescope, launched in 2013 by the European Space Agency, began observing the universe the following year. Astronomers have used Gaia’s observations to discover previously unknown structures in the Milky Way, helping them piece together the history of the galaxy. The telescope’s dataset has also provided astronomers with the positions, distances and movements for nearly 2 billion stars in the galaxy.

In 2022, study coauthor Hans-Walter Rix and his colleagues used Gaia to peer into the heart of the Milky Way and discovered the oldest stars ever found in the galaxy during their “galactic archaeology” observations. An analysis of data from nearly 6 million stars observed by Gaia and the Sloan Digital Sky Survey revealed two streams that appeared to stand out from the rest.

The survey data contained details about the chemical composition of the stars.

“We observed that, for a certain range of metal-poor stars, stars were crowded around two specific combinations of energy and angular momentum,” Malhan said.

Shakti and Shiva are near the Milky Way’s heart, and each stream is estimated to include the mass of about 10 million suns. Here, the ancient stars are all similar in age, orbital path and composition, which helped astronomers determine that both streams were likely threads from an outside source that wove together and became part of the Milky Way.

The distribution of Shakti (yellow) and Shiva (blue) stars can be seen near the heart of the Milky Way. 

ESA/Gaia/DPAC/K. Malhan

The researchers compared the discovery of Shiva and Shakti to finding the initial traces of an ancient settlement that eventually grew to become a large, modern city.

“The stars there are so ancient that they lack many of the heavier metal elements created later in the Universe’s lifetime. These heavy metals are those forged within stars and scattered through space when they die. The stars in our galaxy’s heart are metal-poor, so we dubbed this region the Milky Way’s ‘poor old heart,’” said Rix, director of the Max Planck Institute for Astronomy’s department of galaxies and cosmology in Germany, in a statement.

“Until now, we had only recognised these very early fragments that came together to form the Milky Way’s ancient heart. With Shakti and Shiva, we now see the first pieces that seem comparably old but located further out. These signify the first steps of our galaxy’s growth towards its present size.”

XXXXX

The Max Planck Institute for Astronomy on Thursday announced that astronomers have discovered what could be the earliest building blocks of the Milky Way, named “Shiva” and “ “Shakti. These seem to be the remnants of the two galaxies that merged between 12 and 13 billion years ago with an earlier version of the Milky Way, contributing to its growth.

Astronomers from the institute named the components Shakti and Shiva and identified them after combining data from the European Space Agency’s Gaia satellite and the SDSS survey. This can be thought of like finding traces of an initial settlement that eventually grew into a metropolitan city, albeit on a cosmic scale.

—SUBHAM—

TAGS- Milkyway, Galaxy, Shiva, Shakti, New discovery