Researchers discover 2MASS J18082002-5104378 B, a member from the 1^st generation of stars.

Do you get amazed by all the stars that you see in the night sky? A recent study published in the journal ‘The Astrophysical Journal’ shows that scientists have now found something even more exciting, a 13.5-billion-year-old star which is almost entirely made of materials spewed from the Big Bang. The fact that astronomers found one of the oldest stars means that it is quite likely that more similar stars are out there in the universe.

It is quite different from usual stars because it has very low metal content and mass. Despite that, it is present in the ‘Thin Disk’ of the Milky Way which is a rarity. The age of this star has created some doubts in the minds of the researchers that our galactic neighborhood could be 3 billion years older than previous estimates. Kevin Schlaufman, an Assistant Professor of Physics and Astronomy at the John Hopkins University who is the Lead Author of the study, talked about the importance of this finding and said,

“This star is maybe one in 10 million. It tells us something very important about the first generations of stars.”

The research indicates that this star could only be a generation away from the Big Bang as it offers extraordinarily low metallicity. This newly-discovered star broke all the records for the smallest complement of heavy metals for a star. It has been estimated that it has nearly as much heavy metal content as Mercury. On the other hand, the amount of heavy metal content that our sun has is equal to around 14 Jupiters. Similarly, the mass of this star is outstandingly low even when compared to the lightest stars known to humanity. Scientists have a 30-star-group called the ‘Ultra Metal-poor Stars’. The mass of each star in this group is approximately equal to the Sun. Contrary to that, the star detected by the researching team is only 14% the mass of the sun.

The first stars of the universe, after the Big Bang, were composed of Hydrogen, Helium, and traces of Lithium. Those stars brewed heavier metals in their cores which were spread to all parts of the universe through ‘Supernovae’. Consequently, the next generation of stars was equipped with these metals as they were a part of the star-forming clouds. This process continued for billions of years and the metallicity of stars increased with every cycle of star birth and death.

A couple of decades back, it was believed that only massive stars were possible in the earliest stages of our universe which died quickly by burning all the fuel they had. However, technological advancements changed things dramatically, since then, as astronomical simulations showed that stars with extremely low mass could still exist, 13 billion years after the Big Bang. The latest discovery provides physical evidence for all those claims.

The name given to this new ultra metal-poor star is ‘2MASS J18082002-5104378 B’. According to the study, it is a part of a two-star system orbiting around a common point. Prior to this research, another team of astronomers found the primary star of this star system. They used a high-resolution optical spectrum of its light to measure its composition. The dark lines in the spectrum of a star help in identifying the elements it contains and the analysis of this star showed that it had extremely low metallicity.

Likewise, the researchers of that group detected an unusual behavior in the star system which pointed towards the presence of a black hole or neutron star. The team of Schlaufman began their study to confirm that idea but were able to discover much smaller, secondary star of the system. What made this discovery even bigger was that the astronomers were able to infer the mass of this star. They studied the wobble of the primary star caused by the gravitational tug of 2MASS J18082002-5104378 B to achieve this feat. Schlaufman mentioned that this is a vital finding because it has opened up the possibility of observing even older stars. He said,

“If our inference is correct, then low-mass stars that have a composition exclusively the outcome of the Big Bang can exist. Even though we have not yet found an object like that in our galaxy, it can exist.”