News Brief
Mount Abu Telescope
In a significant development, a team of scientists from the Physical Research Laboratory (PRL), Ahmedabad, have discovered a new exoplanet, TOI-6038A b, a dense sub-Saturn-sized planet in a wide binary system, according to a ISRO statement.
The planet has a mass of 78.5 Earth masses and a radius of 6.41 Earth radii, orbiting a bright, metal-rich F-type star every 5.83 days in a circular orbit.
TOI-6038A b lies in the transition region between Neptune-like and gas giant exoplanets, classified as a “Sub-Saturn”—a category absent in our solar system. This makes it a unique subject for studying planetary formation and evolution.
This marks the second exoplanet discovery using the advanced PARAS-2 spectrograph, attached to the 2.5-meter telescope at PRL's Mount Abu Observatory in Gurushikhar, Mount Abu.
It is also the fifth exoplanet detection using the combined efforts of the PARAS-1 and PARAS-2 spectrographs, underscoring India's growing expertise in astronomical instrumentation.
The PARAS-2 spectrograph is Asia's highest-resolution stabilised radial velocity (RV) spectrograph.
The precise RV data from PARAS-2, along with high-spatial resolution speckle imaging from PRL’s telescope, played a crucial role in confirming the planetary nature of the transit signal.
TOI-6038A b has a high density of 1.62 g/cm³, placing it among the denser sub-Saturns.
Scientists believe it formed through unique mechanisms such as high-eccentricity tidal migration (HEM) or early disk-driven migration.
The presence of this wide binary companion raises questions about its influence on the planet’s orbit.
"While the companion could influence the planet's orbit via secular perturbations, initial analyses suggest these effects may not fully explain its close-in orbit," ISRO said.
Notably, TOI-6038A b is only the fifth sub-Saturn exoplanet discovered in a binary system.
Preliminary analysis of TOI-6038A b’s internal structure suggests it has a massive rocky core, making up approximately three-fourths (0.75) of its total mass, with the remaining mass consisting of a hydrogen-helium envelope.
This provides key insights into the transition between terrestrial planets and gas giants.
The brightness of the TOI-6038A system makes it an ideal candidate for atmospheric characterisation and spin-orbit alignment studies, which could refine existing theories on exoplanet migration.
Additionally, further investigations into undetected companions in the system may help scientists understand the forces shaping its evolution.