Understanding planet and satellite formation with ALMA and VLT Lecture by Dr. Trisha Bhowmik, FONDECYT Postdoctoral fellow, Universidad Diego Portales, Santiago, Chile (9 February, 2026)

 

The Energy Club of the Department of Physics organized an insightful guest lecture on the fundamental processes of planetary and satellite formation. The event commenced with a formal introduction of the guest speaker, Dr. Trisha Bhowmik, by Dr. S. P. Das, who highlighted her significant contributions to the field of astrophysics and her current research in Chile. The seminar aimed to bridge the gap between our understanding of the Solar System’s architecture and the diverse configurations observed in distant protoplanetary environments.

Dr. Bhowmik’s presentation focused on the ODISEA project (Ophiuchus DIsk Survey Employing ALMA), which provides a comprehensive look at 100 planet-forming disks within the Ophiuchus molecular cloud. Using the Atacama Large Millimeter/submillimeter Array (ALMA) at 400 GHz, her team analyzed 55 faint disks at a high resolution of 7 au and 45 brighter disks at 28 au. This high-resolution imaging allowed for the study of radial profiles and substructures such as rings and gaps, which serve as footprints of early planet formation.

A compelling segment of the talk addressed a major discrepancy between theoretical models and observational data. While planet formation theory suggests that younger, "embedded" disks (≤ 1 Myr) should be largely featureless compared to older Class II disks, Dr. Bhowmik’s findings revealed a surprising similarity: 66% of embedded disks and 57% of Class II disks were found to be featureless. She proposed that pressure bumps within the gas disks might be responsible for this phenomenon, as they can trap dust grains and halt the structural evolution that leads to visible rings and gaps.

The lecture then transitioned from the macro-scale of disks to the micro-scale search for exo-satellites around brown dwarfs (BDs) and giant exoplanets. Given that our Solar System contains over 200 moons, it is statistically probable that giant exoplanets host similar companions. Dr. Bhowmik detailed the use of High-Contrast Imaging (HCI) via the SPHERE instrument on the Very Large Telescope (VLT). She explained the "negative fake injection" technique, which models and suppresses the glare of a host companion to reveal faint nearby signals, focusing on targets like GQ Lup B and PZ Tel B.

The seminar concluded with a discussion on the current limits of detection. While confirmed exo-satellites remain elusive, Dr. Bhowmik presented post-processed residual images and mass-limited plots that set crucial benchmarks for future observations with ELT-class telescopes. Following the technical presentation, Prof. Dr. R. G. Sonkawade delivered the presidential remarks, emphasizing the importance of high-resolution instrumentation in solving cosmic mysteries. The program concluded with a formal vote of thanks by Dr. V. S. Kumbhar, acknowledging the efforts of the Energy Club and the speaker for an enriching academic session.