Astronomers spot blue straggler star hosting brown dwarf companion

A team of astronomers from several institutions has made the first confirmed discovery of a rogue blue star hosting a brown dwarf companion in a very compact binary system.

This discovery, made by a team from the Indian Institute of Astrophysics (IIA), Aryabhatta Research Institute of Observational Sciences (ARIES), Gauhati University and INAF-Catania Astrophysical Observatory, Italy, could reshape astronomers’ understanding of how stars evolve.

Brighter and bluer

Stray blue stars have long puzzled scientists, appearing brighter and bluer than main sequence closures in star clusters, defying standard stellar evolution because all cluster stars are expected to be of similar age, according to the Ministry of Science and Technology.

The team comprised Ali Hasan Sheikh, Biman J. Medhi from Gauhati University, Sergio Messina from INAF-Catania, Annapurni Subramanium and Ram Sagar from IIA and Neelam Panwar from ARIES. He found that the system has an exceptionally short orbital period of about 5.6 hours (0.234 days) and contains the lightest companion ever detected around a rogue blue star with a mass of about 0.056 times the mass of the Sun, placing it well below the hydrogen burning limit.

The study, published in the journal ‘Monthly Notices of the Royal Astronomical Society: Letters’, reveals the shortest-period binary system ever discovered in the “brown dwarf desert”, a region where such companions are thought to be extremely rare.

Accurate models

“What the researchers detected, accompanied by a rapidly rotating blue rogue star and a substellar brown dwarf, is an object too massive to be a planet, but too small to have ignited as a true star. The study advances fundamental scientific knowledge by improving our understanding of how stars evolve, interact and survive in extreme environments, which is essential for creating accurate models of stellar and cosmic evolution,” the ministry said. he said.

He added that the results help develop theoretical models of stellar evolution, binary interactions and substellar objects that are widely used in interpreting data from ground-based observatories and space missions.