Mizoram University scientists in collaboration of international team discover rare brown dwarf near stellar boundary
Scientists from Mizoram University, alongside an international team, discovered TOI-7154b, a rare brown dwarf near the hydrogen-burning limit, using the PARAS-2 spectrograph at PRL’s Mount Abu Observatory in Rajasthan. The object, initially flagged as an exoplanet candidate by NASA’s TESS, orbits its Sun-like host star TOI-7154 every 8.86 days with a mass 72 times that of Jupiter, offering insights into the poorly understood boundary between stars and planets.
A team of scientists from Mizoram University, led by Dr. Lalthakimi Zadeng, collaborated with researchers from the Physical Research Laboratory (PRL) and international institutions to discover TOI-7154b, a rare brown dwarf near the stellar boundary. The object was first identified as a potential exoplanet candidate by NASA’s Transiting Exoplanet Survey Satellite (TESS) but was later confirmed as a brown dwarf through advanced spectroscopic observations. Using the PARAS-2 spectrograph at PRL’s Mount Abu Observatory in Rajasthan, astronomers conducted radial velocity measurements to determine TOI-7154b’s mass, orbital motion, and physical properties. Additional observations from the TRES spectrograph at Mount Hopkins in Arizona supported the findings. The brown dwarf orbits its host star, TOI-7154—a metal-rich G-type star similar to the Sun—every 8.86 days on an eccentric path. TOI-7154b is nearly 72 times the mass of Jupiter but smaller in size, placing it dangerously close to the hydrogen-burning limit that separates brown dwarfs from the smallest stars. Researchers highlight its significance, as such objects are rarely found in close orbits around stars, a region known as the ‘brown dwarf desert.’ The discovery underscores the capabilities of Indian astronomical instruments, including the PARAS-2 spectrograph, which provided high-precision measurements. The study, published in *The Astronomical Journal*, suggests TOI-7154b—estimated to be between four and seven billion years old—could offer critical insights into the transition between massive brown dwarfs and low-mass stars.
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