The history of our galaxy has been further explained by the European Space Agency’s (ESA) Gaia (Global Astrometric Interferometer for Astrophysics) space telescope which has found two unforeseen streams of stars that formed and fused more than 12 billion years ago. Notably, the two streams have been named after the Hindu god ‘Shiva’ and goddess ‘Shakti’ and contributed to the formation of the early Milky Way. Given their extraordinary age, it is possible that they originated before the spiral arms and disc of our current galaxy.
Khyati Malhan of the Max Planck Institute for Astronomy (MPIA) in Germany’s Heidelberg, who presided over the research stated, “When we visualised the orbits of all these stars, two new structures stood out from the rest among stars of a certain chemical composition. We named them Shakti and Shiva.” The researchers were able to ascertain the content and makeup of individual Milky Way stars as well as their orbits through the use of Gaia observations.
She mentioned, “What’s truly amazing is that we can detect these ancient structures at all. 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.”
The mass of each stream is equivalent to roughly 10 million Suns and the stars are between 12 and 13 billion years old, all of which are in relatively similar orbits and have comparable compositions. The distribution pattern points to the possibility that they originated as separate elements that early on in the Milky Way’s existence joined with it. Both streams are oriented toward the centre of the Milky Way. Using a technique known as “galactic archaeology,” Gaia investigated this region of the Milky Way in 2022 and discovered that it was home to the earliest stars in the entire galaxy, all of which were born before the Milky Way’s disc had even fully formed.
Co-author Hans-Walter Rix, who is also affiliated with MPIA and served as the primary “galactic archaeologist” for the 2022 study remarked, “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’.”
He pointed out, “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.”
The two streams are not the same, despite their close similarities. ‘Shiva’ stars revolve closer to the centre of the Milky Way whilst ‘Shakti’ stars orbit more circularly. The streams’ names are aptly inspired by a Hindu philosophical pair of deities who come together to form the universe (or macrocosm).
The Milky Way’s current tidy spiral pattern is considerably different from what it looked like around 12 billion years ago. Our galaxy is considered to have formed when several irregular, lengthy strands of gas and dust came together, created stars and wrapped around one another to initiate the formation of our galaxy. Shaki and Shiva appear to be two of these elements, further Gaia data releases could provide more information.
Additionally, leveraging Gaia data, Khyati and Hans-Walter created a dynamical map of additional known elements that were involved in the birth of our galaxy. Among them are Pontus, Arjuna/Sequoia/I’itoi, LMS1/Wukong and Gaia-Sausage-Enceladus. Gaia has spent the last ten years constructing the intricate family tree of the Milky Way, which includes all of these star clusters.
Timo Prusti, Project Scientist for Gaia at ESA conveyed, “Revealing more about our galaxy’s infancy is one of Gaia’s goals, and it’s certainly achieving it. We need to pinpoint the subtle yet crucial differences between stars in the Milky Way to understand how our galaxy formed and evolved. This requires incredibly precise data – and now, thanks to Gaia, we have that data. As we discover surprise parts of our galaxy like the ‘Shiva’ and ‘Shakti’ streams, we’re filling the gaps and painting a fuller picture of not only our current home but our earliest cosmic history.”
Meanwhile, the Working Group for Planetary System Nomenclature of the International Astronomical Union (IAU) has approved “Shiv-Shakti,” the landing site for the country’s lunar mission Chandrayaan 3. Six months have passed since Prime Minister Narendra Modi revealed the name of the location of the Vikram lander’s touchdown. Now, the spot has gained international recognition.
The gazzette read, “Compound word from Indian mythology that depicts the masculine (‘Shiva’) and feminine (‘Shakti’) duality of nature; Landing site of Chandrayaan-3’s Vikram lander.” “Shiva-Shakti” is a compound name in which ‘Shiva’ is the identified masculine consciousness and ‘Shakti’ is the identified feminine divine energy.
The International Astronomical Union Working Group for Planetary System Nomenclature has accepted the name Statio “Shiv-Shakti” for the landing site of Chandrayaan-3’s Vikram lander, according to the Gazetteer of Planetary Nomenclature, which offers comprehensive information regarding planetary names approved by the organisation.
