In a groundbreaking discovery, scientists have found a new kind of stellar chemistry in a faraway star known as A980, located 25,800 light-years away in the Ophiuchus Constellation. This unusual star, part of the rare Extreme Helium (EHe) class, has been revealed to contain a surprising amount of germanium, a metallic element not previously observed in this type of star.
Originally classified as a hydrogen-deficient carbon star—a peculiar group of stars that lack hydrogen—A980 intrigued astronomers at the Indian Institute of Astrophysics (IIA) in Bengaluru. When they observed its light using the Hanle Echelle Spectrograph on the Himalayan Chandra Telescope in Ladakh, they noticed something unexpected. The spectrum, which acts like a fingerprint for stars, showed patterns similar to another rare star, LS IV -14° 109, known as a cool EHe star.
EHe stars are fascinating because they are largely composed of helium, likely formed from the dramatic collision of two white dwarf stars—one rich in carbon and oxygen, and the other in helium. The discovery of germanium in A980, specifically in its singly-ionized form (Ge II), marks a significant first, as germanium had never been detected in EHe stars before. Ajay Saini, a Ph.D. student who led the study, expressed surprise at this finding, noting that germanium is about eight times more abundant in A980 than it is in our Sun.
The researchers believe this discovery sheds light on the complex processes that produce heavy elements in stars. Germanium is thought to form during a stellar phase called the Asymptotic Giant Branch (AGB), when stars expand and produce heavy elements like barium and strontium, before eventually shedding their outer layers to become white dwarfs.
There are two possible scenarios for A980’s unusual chemistry. One possibility is that it is the result of a merger between a helium white dwarf and a carbon-oxygen white dwarf. Alternatively, it could be a Thorne-Żytkow Object (TŻO), a theoretical type of star with a neutron star at its core, known for producing large amounts of germanium through a different process.
This discovery not only adds a new element to the cosmic story of how matter forms, but it also raises deeper questions about the evolution of rare stars and the events that occur during stellar collisions. Dr. Gajendra Pandey, co-author of the study, remarked, “This discovery pushes the boundaries of what we thought we knew about stellar chemistry.”
Published in The Astrophysical Journal, this research represents a major milestone for the Indian Institute of Astrophysics and opens new avenues for understanding the hidden stories written in starlight. High-resolution spectroscopy, the technique used in this study, has proven to be a powerful tool in uncovering the secrets of the universe, encouraging further exploration into the mysteries of stellar evolution.
-Rashmi Kumari
