The new study, led by Anuroop Dasgupta, a doctoral researcher at ESO, YEMS and at the Diego Portales University in Chile, follows up observations of V960 Mon made a couple of years ago. Those observations, made with both SPHERE and the Atacama Large Millimeter/submillimeter Array (ALMA), revealed that the material orbiting V960 Mon is shaped into a series of intricate spiral arms. They also showed that the material is fragmenting, in a process known as ‘gravitational instability’, when large clumps of the material around a star contract and collapse, each with the potential to form a planet or a larger object.

Full ESO press release: Astronomers witness newborn planet sculpting the dust around it.
Open Access paper:
Dasgupta et al. (2025), VLT/ERIS observations of the V960 Mon system: a dust-embedded substellar object formed by gravitational instability?

Since ALMA captured the striking image of HL Tau in 2014—revealing intricate rings and gaps in the disk surrounding a newborn star—astronomers have been trying to understand how such complex structures could form so early. Now, combining observations from the Atacama Large Millimeter/submillimeter Array (ALMA) with advanced simulations, a research team led by Santiago Orcajo from the Instituto de Astrofísica de La Plata (CONICET and Universidad Nacional de La Plata, Argentina), in collaboration with researchers from the YEMS Millennium Nucleus in Chile—including myself—has developed a new model that traces the evolution of these disks through five distinct stages. The results strongly support a planet-driven origin for these substructures and provide fresh insight into how forming planets interact with their natal disks.

Full ALMA press release.
Open Access paper:
Orcajo et al. (2025), The Ophiuchus DIsk Survey Employing ALMA (ODISEA): A Unified Evolutionary Sequence of Planet-driven Substructures Explaining the Diversity of Disk Morphologies

Image credit: NSF/NRAO/S. Dagnello Extract from the press release: “FU Ori has been devouring material for almost 90 years to keep its eruption going. We have finally found an answer to how these young outbursting stars replenish their mass,” explains Antonio Hales, lead author of this research, published today in the Astrophysical Journal, “For the first time we have direct observational evidence of the material fueling the eruptions.” ALMA observations revealed a long, thin stream of carbon monoxide falling onto FU Orionis. This gas didn't appear to have enough fuel to sustain the current outburst. Instead, this accretion streamer is believed to be a leftover from a previous, much larger feature that fell into this young stellar system. “The range of angular scales we are able to explore with a single instrument is truly remarkable. ALMA gives us a comprehensive view of the dynamics of star and planet formation, spanning from large molecular clouds in which hundreds of stars are born, down to the more familiar scales of solar systems,” adds Sebastián Pérez of Universidad de Santiago de Chile (USACH), director of the Millennium Nucleus on Young Exoplanets and their Moons (YEMS) in Chile, and co-author of this research.

Press release by NRAO: Orion’s Erupting Star System Reveals Its Secrets.
Open Access paper:
Hales et al. (2024), Discovery of an Accretion Streamer and a Slow Wide-angle Outflow around FU Orionis

I have played a significant role in broad studies that contextualize eruptive stars, contributing to surveys that present multi-wavelength images to investigate their circumstellar environments (Zurlo et al.; Cieza et al.). My overarching research question seeks to understand the prevalence of the eruptive phase in young stellar objects and its implications for planet formation.

Open Access paper:
Zurlo et al. (2024), The environment around young eruptive stars

Credit: ESO/ALMA (ESO/NAOJ/NRAO)/Weber et al.A spectacular new image released today by the European Southern Observatory gives us clues about how planets as massive as Jupiter could form. Using ESO’s Very Large Telescope (VLT) and the Atacama Large Millimeter/submillimeter Array (ALMA), researchers have detected large dusty clumps, close to a young star, that could collapse to create giant planets. "Our group has been searching for signs of how planets form for over ten years, and we couldn't be more thrilled about this incredible discovery," says Sebastián Pérez from the University of Santiago, Chile.

Full ESO press release.
Open Access paper:
Weber et al. (2024), Spirals and Clumps in V960 Mon: Signs of Planet Formation via Gravitational Instability around an FU Ori Star?

I have been deeply involved in several research projects focused on the observational study of eruptive stars. My work has particularly concentrated on the FU Orionis system, where I have explored the intricate binary interactions and the dynamic flows of gas surrounding the system, ranging from scales of tens of AU to thousands of AU. This research has been conducted primarily in collaboration with Antonio Hales from NRAO and Philipp Weber, a promising young postdoc from the YEMS Nucleus.

Open Access paper:
Pérez et al. (2020), Resolving the FU Orionis System with ALMA: Interacting Twin Disks?

We used the powerful Atacama Large Millimeter/submillimeter Array to study the young star HD 100546, which is surrounded by a disk with a large gap in the dust. Our high-resolution observations revealed intricate patterns of ridges and trenches within this dust ring, and a very strong "kink" in the gas movement that suggest the presence of some kind of local perturbation. These kinks or wiggles in the velocity field hint at complex interactions in the disk, possibly involving vertical gas flows or additional hidden objects. Our findings help us understand how planets might form and shape their surroundings.

Open Access paper:
Pérez et al. (2020), Long Baseline Observations of the HD 100546 Protoplanetary Disk with ALMA.

The migration of planetary cores embedded in a protoplanetary disk is an important mechanism within planet-formation theory, relevant for the architecture of planetary systems. Consequently, planet migration is actively discussed, yet often results of independent theoretical or numerical studies are unconstrained due to the lack of observational diagnostics designed in light of planet migration. In this work we follow the idea of inferring the migration behavior of embedded planets by means of the characteristic radial structures that they imprint in the disk’s dust density distribution.

Open Access paper:
Weber et al. (2019), Predicting the Observational Signature of Migrating Neptune-sized Planets in Low-viscosity Disks.

ALMA has seen a plethora of rings and gaps in almost all protoplanetary disks it has observed at high resolution, yet the origins of these structures remain a matter of intense debate. As the quality of the observations increases, the ringed structures grow in number and complexity, challenging a simple interpretation based on planetary origins. The new ALMA observations of HD169142, a protoplanetary disk 370 light-years away in the constellation of Sagittarius, allowed a team led by Sebastian Perez, from University of Santiago (Chile) to explain the seemingly complex architecture of protoplanetary ring systems with the presence of a single migrating low-mass planet.

Full ALMA press release.
Open Access paper:
Pérez et al. (2019), Dust Unveils the Formation of a Mini-Neptune Planet in a Protoplanetary Ring.

To better understand how giant planets form, we need solid evidence of their presence in the gas-rich discs around young stars. Following up on our 2015 kinematic predictions, we explore how planets interacting with these discs create distinct patterns in the movement of gas and proposed that these are best detected in residual moment maps, which we can observe using specific molecular emissions. By running 3D simulations, we found that giant planets leave strong kinematic signatures, such as changes in gas rotation and flows, which can be detected with high-resolution instruments like the Atacama Large Millimeter/submillimeter Array. These signatures allow us to indirectly spot planets and could eventually help us estimate their mass.

Open Access paper:
Pérez et al. (2018), Observability of planet–disc interactions in CO kinematics.

In 2015, I proposed an innovative method to detect planets, particularly those still forming within protoplanetary disks. This method, now known as "disk kinematics," has emerged as one of the most promising approaches for identifying planets in formation and gaining insights into the dynamics of planet formation. The effectiveness of this method has been validated through the detection of several forming planets in nearby protoplanetary disks, marking a significant advancement in our understanding of how planets develop within these environments.

Open Access paper:
Pérez et al. (2015), Planet Formation Signposts: Observability Of Circumplanetary Disks Via Gas Kinematics

A piece in the puzzle of how planets form has been unlocked thanks to new insight on planet forming systems. Planets are thought to form in disks of gas and dust that surround new born stars. Assuming that these protoplanetary disks lie in a single plane, all proto-planets tend to be contained in that plane too, much like the planets in our Solar System revolve in coplanar orbits. In Marino et al. (2015), we demonstrated for the first time that disks are not necessarily flat and that the presence of shadows in a planet forming system requires at least two tilted disks: an inner disk practically perpendicular to its outer regions.

Press release:
Shadows cast by a warp in a planet forming system (Universidad de Chile press release)
Open Access paper:
Marino et al. (2015), Shadows Cast by a Warp in the HD 142527 Protoplanetary Disk.

• Philipp Weber (postdoc FONDECYT/YEMS)
• James Miley (postdoc FONDECYT/YEMS)
• Camilo Gonzalez-Ruilova (postdoc DICYT/YEMS)
• Fernando Castillo (masters, physics Usach)
• Ian Rickmers (undergrad, informatics engineering Usach, with F. Rannou)
• David Balero (undergrad, informatics engineering Usach, with P. Román)
• Alma Vidal (masters, informatics engineering Usach)

• Kevin Diaz (undergrad, informatics engineering Usach, with F. Rannou)
• Javiera Paterakis (undergrad, physics engineering student Usach, with F. Rannou)
• Irma Fuentes (postdoc DICYT/YEMS, with Carla Hernández)
• Belen Rickmers (undergrad, informatics engineering Usach, with F. Rannou)
• Dennis Urrutia (undergrad, informatics engineering Usach, with P. Román)
• Bayron Monsalvez (undergrad, computing Usach)
• Felipe Alarcón (Master's student UChile). Then, obtained a PhD position at Michigan University.
• Marcelos Barraza (Master's student UChile). Then, obtained a PhD position at Heidelberg University. Now a postdoc at MIT.